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Turtles are an
order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
of
reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates ( lizards and snakes) and rhynchoce ...
s known as Testudines, characterized by a special
shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard o ...
developed mainly from their ribs. Modern turtles are divided into two major groups, the
Pleurodira The Pleurodira are one of the two living suborders of turtles, the other being the Cryptodira. The division between these two suborders represents a very deep evolutionary divide between two very different types of turtles. The physical differen ...
(side necked turtles) and
Cryptodira The Cryptodira ('' el, hidden neck'') are a suborder of Testudines that includes most living tortoises and turtles. Cryptodira differ from Pleurodira (side-necked turtles) in that they lower their necks and pull the heads straight back into the ...
(hidden necked turtles), which differ in the way the head retracts. There are 360 living and recently extinct
species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
of turtles, including land-dwelling
tortoise Tortoises () are reptiles of the family Testudinidae of the order Testudines (Latin: ''tortoise''). Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like other ...
s and freshwater
terrapin Terrapins are one of several small species of turtle (order Testudines) living in fresh or brackish water. Terrapins do not form a taxonomic unit and may not be closely related. Many belong to the families Geoemydidae and Emydidae. The name "t ...
s. They are found on most continents, some islands and, in the case of
sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhead, ...
s, much of the ocean. Like other
amniotes Amniotes are a clade of tetrapod vertebrates that comprises sauropsids (including all reptiles and birds, and extinct parareptiles and non-avian dinosaurs) and synapsids (including pelycosaurs and therapsids such as mammals). They are distingu ...
(reptiles, birds, and
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s) they breathe air and do not lay eggs underwater, although many species live in or around water. Turtle shells are made mostly of bone; the upper part is the domed
carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the under ...
, while the underside is the flatter plastron or belly-plate. Its outer surface is covered in
scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number w ...
made of
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...
, the material of hair, horns, and claws. The carapace bones develop from ribs that grow sideways and develop into broad flat plates that join up to cover the body. Turtles are
ectotherm An ectotherm (from the Greek () "outside" and () "heat") is an organism in which internal physiological sources of heat are of relatively small or of quite negligible importance in controlling body temperature.Davenport, John. Animal Life a ...
s or "cold-blooded", meaning that their internal temperature varies with their direct environment. They are generally opportunistic
omnivore An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nut ...
s and mainly feed on plants and animals with limited movements. Many turtles migrate short distances seasonally. Sea turtles are the only reptiles that migrate long distances to lay their eggs on a favored beach. Turtles have appeared in myths and folktales around the world. Some terrestrial and freshwater species are widely kept as pets. Turtles have been hunted for their meat, for use in traditional medicine, and for their shells. Sea turtles are often killed accidentally as
bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...
in fishing nets. Turtle habitats around the world are being destroyed. As a result of these pressures, many species are extinct or threatened with extinction.


Naming and etymology

The word ''turtle'' is derived from the French or ('turtle,
tortoise Tortoises () are reptiles of the family Testudinidae of the order Testudines (Latin: ''tortoise''). Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like other ...
'). It is a
common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...
and may be used without knowledge of taxonomic distinctions. In North America, it may denote the order as a whole. In Britain, the name is used for
sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhead, ...
s as opposed to freshwater
terrapin Terrapins are one of several small species of turtle (order Testudines) living in fresh or brackish water. Terrapins do not form a taxonomic unit and may not be closely related. Many belong to the families Geoemydidae and Emydidae. The name "t ...
s and land-dwelling tortoises. In Australia, which lacks true tortoises (family Testudinidae), non-marine turtles were traditionally called tortoises, but more recently turtle has been used for the entire group. The name of the order, ''Testudines'' ( ), is based on the
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
word for tortoise, ; and was coined by German naturalist
August Batsch August Johann Georg Karl Batsch (28 October 1761 – 29 September 1802) was a German naturalist. He was a recognised authority on mushrooms, and also described new species of ferns, bryophytes, and seed plants. Life and career Batsch was bor ...
in 1788. The order has also been historically known as ''Chelonii'' ( Latreille 1800) and ''Chelonia'' (Ross and Macartney 1802), which are based on the Ancient Greek word for tortoise: (). Testudines is the official order name due to the
principle of priority 270px, '' valid name. Priority is a fundamental principle of modern botanical nomenclature and zoological nomenclature. Essentially, it is the principle of recognising the first valid application of a name to a plant or animal. There are two asp ...
. The term chelonian is used as a formal name for members of the group.


Anatomy and physiology


Size

The largest living species of turtle (and fourth-largest
reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates ( lizards and snakes) and rhynchoce ...
) is the
leatherback turtle The leatherback sea turtle (''Dermochelys coriacea''), sometimes called the lute turtle or leathery turtle or simply the luth, is the largest of all living turtles and the heaviest non- crocodilian reptile, reaching lengths of up to and weight ...
, which can reach over in length and weigh over . The largest known turtle was '' Archelon ischyros'', a
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...
sea turtle up to long, wide between the tips of the front flippers, and estimated to have weighed over . The smallest living turtle is ''
Chersobius signatus ''Chersobius signatus'' is the world's smallest species of tortoise (family Testudinidae). The species is commonly known as the speckled tortoise and also known locally as the speckled padloper and internationally as the speckled Cape tortoise. ...
'' of South Africa, measuring no more than in length and weighing .


Shell

The shell of a turtle is unique among
vertebrate Vertebrates () comprise all animal taxon, taxa within the subphylum Vertebrata () (chordates with vertebral column, backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the ...
s and serves to protect the animal and provide shelter from the elements. It is primarily made of 50–60 bones and consists of two parts: the domed, dorsal (back)
carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the under ...
and the flatter, ventral (belly) plastron. They are connected by lateral (side) extensions of the plastron. The carapace is fused with the vertebrae and ribs while the plastron is formed from bones of the
shoulder girdle The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists of ...
,
sternum The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Sha ...
, and
gastralia Gastralia (singular gastralium) are dermal bones found in the ventral body wall of modern crocodilians and tuatara, and many prehistoric tetrapods. They are found between the sternum and pelvis, and do not articulate with the vertebrae. In ...
(abdominal ribs). During development, the ribs grow sideways into a carapacial ridge, unique to turtles, entering the
dermis The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided i ...
(inner skin) of the back to support the carapace. The development is signaled locally by proteins known as
fibroblast growth factor Fibroblast growth factors (FGF) are a family of cell signalling proteins produced by macrophages; they are involved in a wide variety of processes, most notably as crucial elements for normal development in animal cells. Any irregularities in the ...
s that include
FGF10 Fibroblast growth factor 10 is a protein that in humans is encoded by the ''FGF10'' gene. Function The protein encoded by this gene is a member of the fibroblast growth factor (FGF) family. FGF family members possess broad mitogenic and cell ...
. The shoulder girdle in turtles is made up of two bones, the scapula and the
coracoid A coracoid (from Greek κόραξ, ''koraks'', raven) is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is prese ...
. Both the shoulder and pelvic girdles of turtles are located within the shell and hence are effectively within the rib cage. The trunk ribs grow over the shoulder girdle during development. The shell is covered in
epidermal The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water relea ...
(outer skin) scales known as
scute A scute or scutum (Latin: ''scutum''; plural: ''scuta'' "shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of birds. The term is also used to describe the anterior po ...
s that are made of
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...
, the same substance that makes up hair and fingernails. Typically, a turtle has 38 scutes on the carapace and 16 on the plastron, giving them 54 in total. Carapace scutes are divided into "marginals" around the margin and "vertebrals" over the vertebral column, though the scute that overlays the neck is called the "cervical". "Pleurals" are present between the marginals and vertebrals. Plastron scutes include gulars (throat), humerals, pectorals, abdominals, and anals. Side-necked turtles additionally have "intergular" scutes between the gulars. Turtle scutes are usually structured like mosaic tiles, but some species, like the
hawksbill sea turtle The hawksbill sea turtle (''Eretmochelys imbricata'') is a critically endangered sea turtle belonging to the family Cheloniidae. It is the only extant species in the genus ''Eretmochelys''. The species has a global distribution, that is large ...
, have overlapping scutes on the carapace. The shapes of turtle shells vary with the adaptations of the individual species, and sometimes with sex. Land-dwelling turtles are more dome-shaped, which appears to make them more resistant to being crushed by large animals. Aquatic turtles have flatter, smoother shells that allow them to cut through the water. Sea turtles in particular have streamlined shells that reduce drag and increase stability in the open ocean. Some turtle species have pointy or spiked shells that provide extra protection from predators and
camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...
against the leafy ground. The lumps of a tortoise shell can tilt its body when it gets flipped over, allowing it to flip back. In male tortoises, the tip of the plastron is thickened and used for butting and ramming during combat. Shells vary in flexibility. Some species, such as
box turtle Box turtle is the common name for several species of turtle. It may refer to those of the genus '' Cuora'' or '' Pyxidea'', which are the Asian box turtles, or more commonly to species of the genus '' Terrapene'', the North American box turtles. ...
s, lack the lateral extensions and instead have the carapace bones fully fused or
ankylosed Ankylosis is a stiffness of a joint due to abnormal adhesion and rigidity of the bones of the joint, which may be the result of injury or disease. The rigidity may be complete or partial and may be due to inflammation of the tendinous or muscular ...
together. Several species have hinges on their shells, usually on the plastron, which allow them to expand and contract.
Softshell turtle The Trionychidae are a taxonomic family of a number of turtle genera, commonly known as softshell turtles. The family was erected by Leopold Fitzinger in 1826. Softshells include some of the world's largest freshwater turtles, though many can ad ...
s have rubbery edges, due to the loss of bones. The leatherback turtle has hardly any bones in its shell, but has thick connective tissue and an outer layer of leathery skin.


Head and neck

The turtle's skull is unique among living
amniote Amniotes are a clade of tetrapod vertebrates that comprises sauropsids (including all reptiles and birds, and extinct parareptiles and non-avian dinosaurs) and synapsids (including pelycosaurs and therapsids such as mammals). They are distin ...
s (which includes reptiles, birds and mammals), it is solid and rigid with no openings for muscle attachment (
temporal fenestrae The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...
). Muscles instead attach to recesses in the back of the skull. Turtle skulls vary in shape, from the long and narrow skulls of softshells to the broad and flattened skull of the
mata mata Matamata () is a town in Waikato, New Zealand. It is located near the base of the Kaimai Ranges, and is a thriving farming area known for Thoroughbred horse breeding and training pursuits. It is part of the Matamata-Piako District, which takes ...
. Some turtle species have developed large and thick heads, allowing for greater muscle mass and stronger bites. Turtles that are carnivorous or
durophagous Durophagy is the eating behavior of animals that consume hard-shelled or exoskeleton bearing organisms, such as corals, shelled mollusks, or crabs. It is mostly used to describe fish, but is also used when describing reptiles, including fossil t ...
(eating hard-shelled animals) have the most powerful bites. For example, the durophagous '' Mesoclemmys nasuta'' has a bite force of . Species that are
insectivorous A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores we ...
,
piscivorous A piscivore () is a carnivorous animal that eats primarily fish. The name ''piscivore'' is derived . Piscivore is equivalent to the Greek-derived word ichthyophage, both of which mean "fish eater". Fish were the diet of early tetrapod evoluti ...
(fish-eating), or
omnivorous An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nut ...
have lower bite forces. Living turtles lack teeth but have beaks made of keratin sheaths along the edges of the jaws. These sheaths may have sharp edges for cutting meat, serrations for clipping plants, or broad plates for breaking
mollusks Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estim ...
. The necks of turtles are highly flexible, possibly to compensate for their rigid shells. Some species, like sea turtles, have short necks while others, such as
snake-necked turtle Chelidae is one of three living families of the turtle suborder Pleurodira, and are commonly called Austro-South American side-neck turtles. The family is distributed in Australia, New Guinea, parts of Indonesia, and throughout most of South Ame ...
s, have long ones. Despite this, all turtle species have eight neck vertebrae, a consistency not found in other reptiles but similar to mammals. Some snake-necked turtles have both long necks and large heads, limiting their ability to lift them when not in water. Some turtles have folded structures in the
larynx The larynx (), commonly called the voice box, is an organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about ...
or
glottis The glottis is the opening between the vocal folds (the rima glottidis). The glottis is crucial in producing vowels and voiced consonants. Etymology From Ancient Greek ''γλωττίς'' (glōttís), derived from ''γλῶττα'' (glôtta), v ...
that vibrate to produce sound. Other species have
elastin Elastin is a protein that in humans is encoded by the ''ELN'' gene. Elastin is a key component of the extracellular matrix in gnathostomes (jawed vertebrates). It is highly elastic and present in connective tissue allowing many tissues in the bo ...
-rich
vocal cord In humans, vocal cords, also known as vocal folds or voice reeds, are folds of throat tissues that are key in creating sounds through vocalization. The size of vocal cords affects the pitch of voice. Open when breathing and vibrating for speech ...
s.


Limbs and locomotion

Due to their heavy shells, turtles are slow-moving on land. A
desert tortoise The desert tortoise (''Gopherus agassizii''), is a species of tortoise in the Family (biology), family Testudinidae. The species is native to the Mojave Desert, Mojave and Sonoran Deserts of the southwestern United States and northwestern Mexic ...
moves at only . By contrast, sea turtles can swim at . The limbs of turtles are adapted for various means of locomotion and habits and most have five toes. Tortoises are specialized for terrestrial environments and have column-like legs with elephant-like feet and short toes. The
gopher tortoise The gopher tortoise (''Gopherus polyphemus'') is a species of tortoise in the family Testudinidae. The species is native to the southeastern United States. The gopher tortoise is seen as a keystone species because it digs burrows that provide s ...
has flattened front limbs for digging in the substrate. Freshwater turtles have more flexible legs and longer toes with
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, giving them thrust in the water. Some of these species, such as
snapping turtles The Chelydridae is a family of turtles that has seven extinct and two extant genera. The extant genera are the snapping turtles, '' Chelydra'' and '' Macrochelys''. Both are endemic to the Western Hemisphere. The extinct genera are '' Acherontem ...
and
mud turtle ''Kinosternon'' is a genus of small aquatic turtles from the Americas known commonly as mud turtles. Geographic range They are found in the United States, Mexico, Central America, and South America. The greatest species richness is in Mexico, a ...
s, mainly walk along the water bottom, as they would on land. Others, such as terrapins, swim by paddling with all four limbs, switching between the opposing front and hind limbs, which keeps their direction stable. Sea turtles and the
pig-nosed turtle The pig-nosed turtle (''Carettochelys insculpta''), also known as the pitted-shelled turtle or Fly River turtle, is a species of turtle native to northern Australia and southern New Guinea. It is the only living member of the family Carettochel ...
are the most specialized for swimming. Their front limbs have evolved into flippers while the shorter hind limbs are shaped more like rudders. The front limbs provide most of the thrust for swimming, while the hind limbs serve as stabilizers. Sea turtles such as the
green sea turtle The green sea turtle (''Chelonia mydas''), also known as the green turtle, black (sea) turtle or Pacific green turtle, is a species of large sea turtle of the family Cheloniidae. It is the only species in the genus ''Chelonia''. Its range exten ...
rotate the front limb flippers like a bird's wings to generate a propulsive force on both the upstroke and on the downstroke. This is in contrast to similar-sized freshwater turtles (measurements having been made on young animals in each case) such as the
Caspian turtle The Caspian turtle or striped-neck terrapin (''Mauremys caspica'') is a species of turtle in the family Geoemydidae (=Bataguridae), living in the eastern Mediterranean region from southwestern former USSR and central Iran to Saudi Arabia, Bahrai ...
, which uses the front limbs like the oars of a rowing boat, creating substantial negative thrust on the recovery stroke in each cycle. In addition, the streamlining of the marine turtles reduces drag. As a result, marine turtles produce a propulsive force twice as large, and swim six times as fast, as freshwater turtles. The swimming efficiency of young marine turtles is similar to that of fast-swimming fish of open water, like
mackerel Mackerel is a common name applied to a number of different species of pelagic fish, mostly from the family Scombridae. They are found in both temperate and tropical seas, mostly living along the coast or offshore in the oceanic environment. ...
. Compared to other reptiles, turtles tend to have reduced tails, but these vary in both length and thickness among species and between sexes. Snapping turtles and the big-headed turtle have longer tails; the latter uses it for balance while climbing. The
cloaca In animal anatomy, a cloaca ( ), plural cloacae ( or ), is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles and birds, an ...
is found underneath and at the base, and the tail itself houses the reproductive organs. Hence, males have longer tails to contain the penis. In sea turtles, the tail is longer and more
prehensile Prehensility is the quality of an appendage or organ that has adapted for grasping or holding. The word is derived from the Latin term ''prehendere'', meaning "to grasp". The ability to grasp is likely derived from a number of different origi ...
in males, who use it to grasp mates. Several turtle species have spines on their tails.


Senses

Turtles make use of
vision Vision, Visions, or The Vision may refer to: Perception Optical perception * Visual perception, the sense of sight * Visual system, the physical mechanism of eyesight * Computer vision, a field dealing with how computers can be made to gain und ...
to find food and mates, avoid predators, and orient themselves. The
retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then p ...
's light-sensitive cells include both rods for vision in low light, and
cones A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. A cone is formed by a set of line segments, half-lines, or lines con ...
with three different
photopigment Photopigments are unstable pigments that undergo a chemical change when they absorb light. The term is generally applied to the non-protein chromophore moiety of photosensitive chromoproteins, such as the pigments involved in photosynthesis and p ...
s for bright light, where they have full-color vision. There is possibly a fourth type of cone that detects
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiatio ...
, as hatchling sea turtles respond experimentally to ultraviolet light, but it is unknown if they can distinguish this from longer wavelengths. A freshwater turtle, the
red-eared slider The red-eared slider or red-eared terrapin (''Trachemys scripta elegans'') is a subspecies of the pond slider (''Trachemys scripta''), a semiaquatic turtle belonging to the family Emydidae. It is the most popular pet turtle in the United States ...
, has an exceptional seven types of cone cell. Sea turtles orient themselves on land by night, using visual features detected in dim light. They can use their eyes in clear surface water, muddy coasts, the darkness of the deep ocean, and also above water. Unlike in terrestrial turtles, the
cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical powe ...
, the curved surface that lets light into the eye, does not help to focus light on the retina, so focusing underwater is handled entirely by the lens, behind the cornea. The cone cells contain oil droplets placed to shift perception toward the red part of the spectrum, improving color discrimination. Visual acuity, studied in hatchlings, is highest in a horizontal band with retinal cells packed about twice as densely as elsewhere. This gives the best vision along the visual horizon. Sea turtles do not appear to use
polarized light Polarization (also polarisation) is a property applying to transverse waves that specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of th ...
for orientation as many other animals do. The deep-diving leatherback turtle lacks specific adaptations to low light, such as large eyes, large lenses, or a reflective tapetum. It may rely on seeing the
bioluminescence Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some ...
of prey when hunting in deep water. Turtles have no ear openings; the
eardrum In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit sound from the a ...
is covered with scales and encircled by a bony
otic capsule The bony labyrinth (also osseous labyrinth or otic capsule) is the rigid, bony outer wall of the inner ear in the temporal bone. It consists of three parts: the vestibule, semicircular canals, and cochlea. These are cavities hollowed out of the s ...
, which is absent in other reptiles. Their hearing thresholds are high in comparison to other reptiles, reaching up to 500 Hz in air, but underwater they are more attuned to lower frequencies. The
loggerhead sea turtle The loggerhead sea turtle (''Caretta caretta'') is a species of oceanic turtle distributed throughout the world. It is a marine reptile, belonging to the family Cheloniidae. The average loggerhead measures around in carapace length when fully ...
has been shown experimentally to respond to low sounds, with maximal sensitivity between 100 and 400 Hz. Turtles have
olfactory The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, it ...
(smell) and vomeronasal receptors along the nasal cavity, the latter of which are used to detect chemical signals. Experiments on green sea turtles showed they could learn to respond to a selection of different odorant chemicals such as
triethylamine Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. It is also abbreviated TEA, yet this abbreviation must be used carefully to avoid confusion with triethanolamine or tetraethylammonium, for which TEA ...
and
cinnamaldehyde Cinnamaldehyde is an organic compound with the formula(C9H8O) C6H5CH=CHCHO. Occurring naturally as predominantly the ''trans'' (''E'') isomer, it gives cinnamon its flavor and odor. It is a phenylpropanoid that is naturally synthesized by the sh ...
, which were detected by olfaction in the nose. Such signals could be used in navigation.


Breathing

The rigid shell of turtles is not capable of expanding and making room for the lungs, as in other amniotes, so they have had to evolve special adaptations for respiration. The lungs of turtles are attached directly to the carapace above while below, connective tissue attaches them to the organs. They have multiple lateral (side) and medial (middle) chambers (the numbers of which vary between species) and one terminal (end) chamber. The lungs are ventilated using specific groups of abdominal muscles attached to the organs that pull and push on them. Specifically, it is the turtle's large liver that compresses the lungs. Underneath the lungs, in the coelomic cavity, the liver is connected to the right lung by the
root In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the sur ...
, and the stomach is directly attached to the left lung, and to the liver by a
mesentery The mesentery is an organ that attaches the intestines to the posterior abdominal wall in humans and is formed by the double fold of peritoneum. It helps in storing fat and allowing blood vessels, lymphatics, and nerves to supply the intesti ...
. When the liver is pulled down, inhalation begins. Supporting the lungs is a wall or
septum In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interatr ...
, which is thought to prevent them from collapsing. During exhalation, the contraction of the
transversus abdominis muscle The transverse abdominal muscle (TVA), also known as the transverse abdominis, transversalis muscle and transversus abdominis muscle, is a muscle layer of the anterior and lateral (front and side) abdominal wall which is deep to (layered below) th ...
propels the organs into the lungs and expels air. Conversely, during inhalation, the relaxing and flattening of the oblique abdominis muscle pulls the transversus back down, allowing air back into the lungs. Although many turtles spend large amounts of their lives underwater, all turtles breathe air and must surface at regular intervals to refill their lungs. Depending on the species, immersion periods vary between a minute and an hour. Some species can respire through the cloaca, which contains large sacs that are lined with many finger-like projections that take up dissolved
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well ...
from the water.


Circulation

Turtles share the linked
circulatory The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
and pulmonary (lung) systems of vertebrates, where the three-chambered heart pumps deoxygenated blood through the lungs and then pumps the returned
oxygenated blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...
through the body's tissues. The cardiopulmonary system has both structural and physiological adaptations that distinguish it from other vertebrates. Turtles have a large lung volume and can move blood through non-pulmonary blood vessels, including some within the heart, to avoid the lungs while they are not breathing. They can hold their breath for much longer periods than other reptiles and they can tolerate the resulting low oxygen levels. They can moderate the increase in acidity during anaerobic (non-oxygen-based) respiration by chemical buffering and they can lie dormant for months, in
aestivation Aestivation ( la, aestas (summer); also spelled estivation in American English) is a state of animal dormancy, similar to hibernation, although taking place in the summer rather than the winter. Aestivation is characterized by inactivity and a ...
or
brumation Dormancy is a period in an organism's life cycle when growth, development, and (in animals) physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be clos ...
. The heart has two atria but only one ventricle. The ventricle is subdivided into three chambers. A muscular ridge enables a complex pattern of blood flow so that the blood can be directed either to the lungs via the
pulmonary artery A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The largest pulmonary artery is the ''main pulmonary artery'' or ''pulmonary trunk'' from the heart, and ...
, or to the body via the
aorta The aorta ( ) is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes ...
. The ability to separate the two outflows varies between species. The leatherback has a powerful muscular ridge enabling almost complete separation of the outflows, supporting its actively swimming lifestyle. The ridge is less well developed in freshwater turtles like the sliders (''
Trachemys ''Trachemys'' is a genus of turtles belonging to the family Emydidae. Members of this genus are native to the Americas, ranging from the Midwestern United States south to northern Argentina, but one subspecies, the red-eared slider (''T. script ...
''). Turtles are capable of enduring periods of anaerobic respiration longer than many other vertebrates. This process breaks down sugars incompletely to
lactic acid Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natur ...
, rather than all the way to carbon dioxide and water as in aerobic (oxygen-based) respiration. They make use of the shell as a source of additional buffering agents for combating increased acidity, and as a sink for lactic acid.


Osmoregulation

In sea turtles, the bladder is one unit and in most freshwater turtles, it is double-lobed. Sea turtle bladders are connected to two small accessory bladders, located at the sides to the neck of the urinary bladder and above the pubis. Arid-living tortoises have bladders that serve as reserves of water, storing up to 20% of their body weight in fluids. The fluids are normally low in
solute In chemistry, a solution is a special type of homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. If the attractive forces between the solvent ...
s, but higher during droughts when the reptile gains
potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosp ...
salts from its plant diet. The bladder stores these salts until the tortoise finds fresh drinking water. To regulate the amount of salt in their bodies, sea turtles and
diamondback terrapin The diamondback terrapin or simply terrapin (''Malaclemys terrapin'') is a species of turtle native to the brackish coastal tidal marshes of the Northeastern and southern United States, and in Bermuda. It belongs to the monotypic genus ''Malaclem ...
s secrete excess salt in a thick sticky substance from their tear glands. Because of this, sea turtles may appear to be "crying" when on land.


Thermoregulation

Turtles, like other reptiles, have a limited ability to regulate their body temperature. This ability varies between species, and with body size. Small pond turtles regulate their temperature by crawling out of the water and basking in the sun, while small terrestrial turtles move between sunny and shady places to adjust their temperature. Large species, both terrestrial and marine, have sufficient mass to give them substantial
thermal inertia In thermodynamics, a material's thermal effusivity, thermal inertia or thermal responsivity is a measure of its ability to exchange thermal energy with its surroundings. It is defined as the square root of the product of the material's thermal co ...
, meaning that they heat up or cool down over many hours. The
Aldabra giant tortoise The Aldabra giant tortoise (''Aldabrachelys gigantea'') is a species of tortoise in the family Testudinidae. The species is endemic to the islands of the Aldabra Atoll in the Seychelles. It is one of the largest tortoises in the world.Pritcha ...
weighs up to some and is able to allow its temperature to rise to some on a hot day, and to fall naturally to around by night. Some giant tortoises seek out shade to avoid overheating on sunny days. On Grand Terre Island, food is scarce inland, shade is scarce near the coast, and the tortoises compete for space under the few trees on hot days. Large males may push smaller females out of the shade, and some then overheat and die. Adult sea turtles, too, have large enough bodies that they can to some extent control their temperature. The largest turtle, the leatherback, can swim in the waters off
Nova Scotia Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland". Most of the population are native Engl ...
, which may be as cold as , while their body temperature has been measured at up to warmer than the surrounding water. To help keep their temperature up, they have a system of countercurrent heat exchange in the blood vessels between their body core and the skin of their flippers. The vessels supplying the head are insulated by fat around the neck.


Behavior


Diet and feeding

Most turtle species are opportunistic omnivores; land-dwelling species are more
herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...
and aquatic ones more
carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other so ...
. Generally lacking speed and agility, most turtles feed either on plant material or on animals with limited movements like mollusks, worms, and insect larvae. Some species, such as the African helmeted turtle and snapping turtles, eat fish, amphibians, reptiles (including other turtles), birds, and mammals. They may take them by
ambush An ambush is a long-established military tactic in which a combatant uses an advantage of concealment or the element of surprise to attack unsuspecting enemy combatants from concealed positions, such as among dense underbrush or behind mo ...
but also scavenge. The
alligator snapping turtle The alligator snapping turtle (''Macrochelys temminckii'') is a large species of turtle in the family Chelydridae. The species is native to freshwater habitats in the United States. ''M. temminckii'' is one of the heaviest freshwater turtles in ...
has a worm-like appendage on its tongue that it uses to lure fish into its mouth. Tortoises are the most herbivorous group, consuming grasses, leaves, and fruits. Many turtle species, including tortoises, supplement their diet with eggshells, animal bones, hair, and droppings for extra nutrients. Turtles generally eat their food in a straightforward way, though some species have special feeding techniques. The
yellow-spotted river turtle The yellow-spotted Amazon river turtle (''Podocnemis unifilis''), also known commonly as the yellow-headed sideneck turtle and the yellow-spotted river turtle, and locally as the taricaya, is one of the largest South American river turtles. It ...
and the
painted turtle The painted turtle (''Chrysemys picta'') is the most widespread native turtle of North America. It lives in slow-moving fresh waters, from southern Canada to northern Mexico, and from the Atlantic to the Pacific. They have been shown to prefer l ...
may
filter feed Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...
by skimming the water surface with their mouth and throat open to collect particles of food. When the mouth closes, the throat constricts and water is pushed out through the nostrils and the gap in between the jaws. Some species employ a "gape-and-suck method" where the turtle opens its jaws and expands its throat widely, sucking the prey in. The diet of an individual within a species may change with age, sex, and season, and may also differ between populations. In many species, juveniles are generally carnivorous but become more herbivorous as adults. With Barbour's map turtle, the larger female mainly eats mollusks while the male usually eats
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, o ...
s.
Blanding's turtle Blanding's turtle (''Emydoidea blandingii'') is a semi-aquatic turtle of the family Emydidae. This species is native to central and eastern parts of Canada and the United States. It is considered to be an endangered species throughout much of its ...
may feed mainly on snails or crayfish depending on the population. The
European pond turtle The European pond turtle (''Emys orbicularis''), also called commonly the European pond terrapin and the European pond tortoise, is a species of long-living freshwater turtle in the family Emydidae. The species is endemic to the Western Palearct ...
has been recorded as being mostly carnivorous much of the year but switching to
water lilies ''Water Lilies'' (or ''Nymphéas'', ) is a series of approximately 250 oil paintings by French Impressionist Claude Monet (1840–1926). The paintings depict his flower garden at his home in Giverny, and were the main focus of his artistic ...
during the summer. Some species have developed specialized diets such as the hawksbill, which eats
sponges Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through t ...
, the leatherback, which feeds on
jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella ...
, and the Mekong snail-eating turtle.


Communication and intelligence

While popularly thought of as mute, turtles make various sounds to communicate. Tortoises may bellow when courting and mating. Various species of both freshwater and sea turtles emit short, low-frequency calls from the time they are in the egg to when they are adults. These vocalizations may serve to create group cohesion when migrating. The oblong turtle has a particularly large vocal range; producing sounds described as clacks, clicks, squawks, hoots, various kinds of chirps, wails, ', grunts, growls, blow bursts, howls, and drum rolls. Play behavior has been documented in some turtle species. In the laboratory,
Florida red-bellied cooter The Florida red-bellied cooter or Florida redbelly turtle (''Pseudemys nelsoni'') is a species of turtle in the family Emydidae. Etymology The specific name, ''nelsoni'', is in honor of American biologist George Nelson (born 1873). Geographic ...
s can learn novel tasks and have demonstrated a long-term memory of at least 7.5 months. Similarly, giant tortoises can learn and remember tasks, and master lessons much faster when trained in groups. Tortoises appear to be able to retain
operant conditioning Operant conditioning, also called instrumental conditioning, is a learning process where behaviors are modified through the association of stimuli with reinforcement or punishment. In it, operants—behaviors that affect one's environment—are c ...
nine years after their initial training. Studies have shown that turtles can navigate the environment using landmarks and a map-like system resulting in accurate direct routes towards a goal. Navigation in turtles have been correlated to high cognition function in the medial cortex region of the brain.


Defense

When sensing danger, a turtle may flee, freeze or withdraw into its shell. Freshwater turtles flee into the water, though the Sonora mud turtle may take refuge on land as the shallow temporary ponds they inhabit make them vulnerable. When startled, a softshell turtle may dive underwater and bury itself under the sea floor. If a predator persists, the turtle may bite or discharge from its cloaca. Several species produce foul-smelling chemicals from musk glands. Other tactics include threat displays and Bell's hinge-back tortoise can play dead. When attacked, big-headed turtle hatchlings squeal, possibly startling the predator.


Migration

Turtles are the only reptiles that migrate long distances, more specifically the marine species that can travel up to thousands of kilometers. Some non-marine turtles, such as the species of ''
Geochelone ''Geochelone'' is a genus of tortoises. ''Geochelone'' tortoises, which are also known as typical tortoises or terrestrial turtles, can be found in southern Asia. They primarily eat plants. Species The genus consists of two extant species: A n ...
'' (terrestrial), ''
Chelydra ''Chelydra'' is one of the two extant genera of the snapping turtle family, Chelydridae, the other being ''Macrochelys'', the much larger alligator snapping turtle. The snapping turtles are native to the Americas, with ''Chelydra'' having th ...
'' (freshwater), and ''
Malaclemys The diamondback terrapin or simply terrapin (''Malaclemys terrapin'') is a species of turtle native to the brackish coastal tidal marshes of the Northeastern and southern United States, and in Bermuda. It belongs to the monotypic genus ''Malaclem ...
'' (estuarine), migrate seasonally over much shorter distances, up to around , to lay eggs. Such short migrations are comparable to those of some lizards, snakes, and crocodilians. Sea turtles nest in a specific area, such as a beach, leaving the eggs to hatch unattended. The young turtles leave that area, migrating long distances in the years or decades in which they grow to maturity, and then return seemingly to the same area every few years to mate and lay eggs, though the precision varies between species and populations. This "natal homing" has appeared remarkable to biologists, though there is now plentiful evidence for it, including from genetics. How sea turtles navigate to their breeding beaches remains unknown. One possibility is imprinting as in
salmon Salmon () is the common name for several commercially important species of euryhaline ray-finned fish from the family Salmonidae, which are native to tributaries of the North Atlantic (genus ''Salmo'') and North Pacific (genus ''Oncorhynchus' ...
, where the young learn the chemical signature, effectively the scent, of their home waters before leaving, and remember that when the time comes for them to return as adults. Another possible cue is the orientation of the
earth's magnetic field Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic ...
at the natal beach. There is experimental evidence that turtles have an effective magnetic sense, and that they use this in
navigation Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...
. Proof that homing occurs is derived from genetic analysis of populations of loggerheads, hawksbills, leatherbacks, and olive ridleys by nesting place. For each of these species, the populations in different places have their own
mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial DN ...
genetic signatures that persist over the years. This shows that the populations are distinct and that homing must be occurring reliably.


Reproduction and lifecycle

Turtles have a wide variety of mating behaviors but do not form pair-bonds or social groups. In green sea turtles, females generally outnumber males. In terrestrial species, males are often larger than females and fighting between males establishes a
dominance hierarchy In biology, a dominance hierarchy (formerly and colloquially called a pecking order) is a type of social hierarchy that arises when members of animal social groups interact, creating a ranking system. A dominant higher-ranking individual is som ...
for access to mates. For most semi-aquatic and bottom-walking aquatic species, combat occurs less often. Males of these species instead may use their size advantage to mate forcibly. In fully aquatic species, males are often smaller than females and rely on
courtship display A courtship display is a set of display behaviors in which an animal, usually a male, attempts to attract a mate; the mate exercises choice, so sexual selection acts on the display. These behaviors often include ritualized movement ("dances"), ...
s to gain mating access to females.


Courtship and mounting

Courtship varies between species, and with habitat. It is often complex in aquatic species, both marine and freshwater, but simpler in the semi-aquatic mud turtles and snapping turtles. A male tortoise bobs his head, then subdues the female by biting and butting her before mounting. The male scorpion mud turtle approaches the female from the rear, and often resorts to aggressive methods such as biting the female's tail or hind limbs, followed by a mounting. Female choice is important in some species, and female green sea turtles are not always receptive. As such, they have evolved behaviors to avoid the male's attempts at copulation, such as swimming away, confronting the male followed by biting or taking up a refusal position with her body vertical, her limbs widely outspread, and her plastron facing the male. If the water is too shallow for the refusal position, the females resort to beaching themselves, as the males do not follow them ashore. All turtles fertilize internally; mounting and copulation can be difficult. In many species, males have a concave plastron that interlocks with the female's carapace. In species like the
Russian tortoise The Russian tortoise (''Testudo horsfieldii''), also commonly known as the Afghan tortoise, the Central Asian tortoise, Horsfield's tortoise, four-clawed tortoise, and the (Russian) steppe tortoise, is a threatened species of tortoise in the fam ...
, the male has a lighter shell and longer legs. The high, rounded shape of box turtles are particular obstacles for mounting. The male
eastern box turtle The eastern box turtle (''Terrapene carolina carolina'') is a subspecies within a group of hinge-shelled turtles normally called box turtles. ''T. c. carolina'' is native to the eastern part of the United States. The eastern box turtle ...
leans backward and hooks onto the back of the female's plastron. Aquatic turtles mount in water, and female sea turtles support the mounting male while swimming and diving. During copulation, the male turtle aligns his tail with the female's so he can insert his penis into her cloaca. Some female turtles can store sperm from multiple males and their egg clutches can have multiple sires.


Eggs and hatchlings

Turtles, including sea turtles, lay their eggs on land, although some lay eggs close near water that rises and falls in level, submerging the eggs. While most species build nests and lay eggs where they forage, some travel miles. The
common snapping turtle The common snapping turtle (''Chelydra serpentina'') is a species of large freshwater turtle in the family Chelydridae. Its natural range extends from southeastern Canada, southwest to the edge of the Rocky Mountains, as far east as Nova Scotia ...
walks on land, while sea turtles travel even further; the leatherback swims some to its nesting beaches. Most turtles create a nest for their eggs. Females usually dig a flask-like chamber in the substrate. Other species lay their eggs in vegetation or crevices. Females choose nesting locations based on environmental factors such as temperature and humidity, which are important for developing embryos. Depending on the species, the number of eggs laid varies from one to over 100. Larger females can lay eggs that are greater in number or bigger in size. Compared to freshwater turtles, tortoises deposit fewer but larger eggs. Females can lay multiple clutches throughout a season, particularly in species that experience unpredictable
monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...
s. Most mother turtles do no more in the way of parental care than covering their eggs and immediately leaving, though some species guard their nests for days or weeks. Eggs vary between rounded, oval, elongated, and between hard- and soft-shelled. Most species have their sex determined by temperature. In some species, higher temperatures produce females and lower ones produce males, while in others, milder temperatures produce males and both hot and cold extremes produce females. There is experimental evidence that the embryos of '' Mauremys reevesii'' can move around inside their eggs to select the best temperature for development, thus influencing their sexual destiny. In other species, sex is determined genetically. The length of incubation for turtle eggs varies from two to three months for temperate species, and four months to over a year for tropical species. Species that live in warm temperate climates can delay their development. Hatching young turtles break out of the shell using an
egg tooth An egg tooth is a temporary, sharp projection present on the bill or snout of an oviparous animal at hatching. It allows the hatchling to penetrate the eggshell from inside and break free. Birds, reptiles, and monotremes possess egg teeth as ha ...
, a sharp projection that exists temporarily on their upper beak. Hatchlings dig themselves out of the nest and find safety in vegetation or water. Some species stay in the nest for longer, be it for overwintering or to wait for the rain to loosen the soil for them to dig out. Young turtles are highly vulnerable to predators, both in the egg and as hatchlings. Mortality is high during this period but significantly decreases when they reach adulthood. Most species grow quickly during their early years and slow down when they are mature.


Lifespan

Turtles can live long lives. The oldest living turtle and land animal is said to be a Seychelles giant tortoise named Jonathan, who turned 187 in 2019. A
Galápagos tortoise The Galápagos tortoise or Galápagos giant tortoise (''Chelonoidis niger'') is a species of very large tortoise in the genus '' Chelonoidis'' (which also contains three smaller species from mainland South America). It comprises 15 subspecies (1 ...
named Harriet was collected by
Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended fr ...
in 1835; it died in 2006, having lived for at least 176 years. Most wild turtles do not reach that age. Turtles keep growing new scutes under the previous scutes every year, allowing researchers to estimate how long they have lived. They also age slowly. The survival rate for adult turtles can reach 99% per year.


Systematics and evolution


Fossil history

Zoologists have sought to explain the evolutionary origin of the turtles, and in particular of their unique shells. In 1914, Jan Versluys proposed that bony plates in the dermis, called
osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amp ...
s, fused to the ribs beneath them, later called the "Polka Dot Ancestor" by Olivier Rieppel. The theory accounted for the evolution of fossil
pareiasaur Pareiasaurs (meaning "cheek lizards") are an extinct clade of large, herbivorous parareptiles. Members of the group were armoured with scutes which covered large areas of the body. They first appeared in southern Pangea during the Middle Permian ...
s from ''
Bradysaurus ''Bradysaurus'' was a large, early and common pareiasaur, the fossils of which are known from the '' Tapinocephalus'' Assemblage Zone (Capitanian age) of the South African Karoo. Along with the similarly large dinocephalia, the bradysaurs const ...
'' to '' Anthodon'', but not for how the ribs could have become attached to the bony dermal plates. More recent discoveries have painted a different scenario for the evolution of the turtle's shell. The
stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other structure * Stipe (mycology), the stem of a mushro ...
-turtles ''
Eunotosaurus ''Eunotosaurus'' (''Latin'': Stout-backed lizard) is an extinct genus of amniote, possibly a close relative of turtles. ''Eunotosaurus'' lived in the late Middle Permian (Capitanian stage) and fossils can be found in the Karoo Supergroup of Sout ...
'' of the Middle
Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...
, ''
Pappochelys ''Pappochelys'' ( meaning "grandfather turtle" in Greek) is an extinct genus of diapsid reptile possibly related to turtles. The genus contains only one species, ''Pappochelys rosinae'', from the Middle Triassic of Germany, which was named by pal ...
'' of the
Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma and ...
, and '' Eorhynchochelys'' of the
Late Triassic The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. Th ...
lacked carapaces and plastrons but had shortened torsos, expanded ribs, and lengthened dorsal vertebrae. Also in the Late Triassic, '' Odontochelys'' had a partial shell consisting of a complete bony plastron and an incomplete carapace. The development of a shell reached completion with the Late Triassic ''
Proganochelys ''Proganochelys'' is an extinct, primitive stem-turtle that has been hypothesized to be the sister taxon to all other turtles creating a monophyletic group, the ''Casichelydia''. ''Proganochelys'' was named by Georg Baur in 1887 as the oldest t ...
'', with its fully developed carapace and plastron. Adaptations that lead to the evolution of the shell may have originally been for digging and a
fossorial A fossorial () animal is one adapted to digging which lives primarily, but not solely, underground. Some examples are badgers, naked mole-rats, clams, meerkats, and mole salamanders, as well as many beetles, wasps, and bees. Prehistoric evid ...
lifestyle. The oldest known members of the Pleurodira lineage are the Platychelyidae, from the
Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...
. The oldest known unambiguous cryptodire is ''
Sinaspideretes ''Sinaspideretes'' is an extinct genus of turtle from the Late Jurassic of China, probably from the Shaximiao Formation. It is considered the earliest and most basal representative of the Trionychia, and is possibly the oldest known member of Cr ...
,'' a close relative of softshell turtles, from the Late Jurassic of China. During the
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...
and
Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configurat ...
, members of the pleurodire families
Bothremydidae Bothremydidae is an extinct family of side-necked turtles (Pleurodira) known from the Cretaceous and Cenozoic. They are closely related to Podocnemididae, and are amongst the most widely distributed pleurodire groups, with their fossils having ...
and
Podocnemididae Podocnemididae is a family of pleurodire (side-necked) turtles, once widely distributed. Most of its 20 genera and 30 species are now extinct. Seven of its eight surviving species are native to South America: the genus '' Peltocephalus'', with ...
became widely distributed in the Northern Hemisphere due to their coastal habits. The oldest known soft-shelled turtles and sea turtles appeared during the
Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous ( chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145  Ma to 100.5 Ma. Geology P ...
. Tortoises originated in Asia during the
Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "daw ...
. A late surviving group of stem-turtles, the
Meiolaniidae Meiolaniidae is an extinct family of large, probably herbivorous stem-group turtles with heavily armored heads and tails known from South America and Australasia. Though once believed to be cryptodires, they are not closely related to any living ...
, survived in Australasia into the
Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...
and Holocene.


External relationships

The turtles' exact ancestry has been disputed. It was believed they were the only surviving branch of the ancient
evolutionary grade A grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit. Definition An evolutionary grade is a group of s ...
Anapsid An anapsid is an amniote whose skull lacks one or more skull openings (fenestra, or fossae) near the temples. Traditionally, the Anapsida are the most primitive subclass of amniotes, the ancestral stock from which Synapsida and Diapsida evolved, ...
a, which includes groups such as
procolophonid Procolophonidae is an extinct family of small, lizard-like parareptiles known from the Late Permian to Late Triassic that were distributed across Pangaea, having been reported from Europe, North America, China, South Africa, South America, Antar ...
s and pareiasaurs. All anapsid skulls lack a temporal opening while all other living amniotes have temporal openings. It was later suggested that the anapsid-like turtle skulls may be due to backward evolution rather than to anapsid descent. Fossil evidence has shown that early stem-turtles possessed small temporal openings. Some early morphological
phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
studies have placed turtles closer to
Lepidosauria The Lepidosauria (, from Greek meaning ''scaled lizards'') is a subclass or superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata includes snakes, lizards, and amphisbaenians. Squamata contains over 9,000 species ...
(
tuatara Tuatara (''Sphenodon punctatus'') are reptiles endemic to New Zealand. Despite their close resemblance to lizards, they are part of a distinct lineage, the order Rhynchocephalia. The name ''tuatara'' is derived from the Māori language and m ...
s,
lizard Lizards are a widespread group of Squamata, squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbae ...
s, and
snake Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more joints ...
s) than to
Archosaur Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avian ...
ia (
crocodilian Crocodilia (or Crocodylia, both ) is an Order (biology), order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous Period (geology), period (Cenomanian St ...
s and birds). By contrast, several
molecular A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...
studies place turtles either within Archosauria, or, more commonly, as a
sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...
to extant archosaurs, though an analysis conducted by Tyler Lyson and colleagues (2012) recovered turtles as the sister group of lepidosaurs instead. Ylenia Chiari and colleagues (2012) analyzed 248
nuclear gene A nuclear gene is a gene whose physical DNA nucleotide sequence is located in the cell nucleus of a eukaryote. The term is used to distinguish nuclear genes from genes found in mitochondria or chloroplasts. The vast majority of genes in eukaryote ...
s from 16 vertebrates and suggested that turtles share a more recent common ancestor with birds and crocodilians. The date of separation of turtles and birds and crocodilians was estimated to be during the Permian. Through
genomic Genomics is an interdisciplinary field of biology focusing on the structure, function, evolution, mapping, and editing of genomes. A genome is an organism's complete set of DNA, including all of its genes as well as its hierarchical, three-dim ...
-scale phylogenetic study of
ultra-conserved element An ultra-conserved element (UCE) was originally defined as a genome segment longer than 200 base pairs (bp) that is absolutely conserved, with no insertions or deletions and 100% identity, between orthologous regions of the human, rat, and mouse gen ...
s (UCEs) to clarify the placement of turtles within reptiles, Nicholas Crawford and colleagues (2012) similarly found that turtles are closer to birds and crocodilians. Using the draft (unfinished) genome sequences of the green sea turtle and the
Chinese softshell turtle The Chinese softshell turtle (''Pelodiscus sinensis'') is a species of softshell turtle that is native to China (Inner Mongolia to Guangxi, including Hong Kong) and Taiwan, with records of escapees—some of which have established introduced po ...
, Zhuo Wang and colleagues (2013) concluded that turtles are likely a sister group of crocodilians and birds. The external phylogeny of the turtles is shown in the
cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...
below.


Internal relationships

Modern turtles and their extinct relatives with a complete shell are classified within the clade Testudinata. The most recent common ancestor of living turtles, corresponding to the split between Pleurodira (side-necked species) and
Cryptodira The Cryptodira ('' el, hidden neck'') are a suborder of Testudines that includes most living tortoises and turtles. Cryptodira differ from Pleurodira (side-necked turtles) in that they lower their necks and pull the heads straight back into the ...
(hidden necked species), is estimated to have occurred around during the Late Triassic. Robert Thompson and colleagues (2021) comment that living turtles have low diversity, relative to how long they existed. Diversity has been stable, according to their analysis, except for a single rapid increase around the Eocene-Oligocene boundary some 30 million years ago, and a large regional extinction at roughly the same time. They suggest that global climate change caused both events, as the cooling and drying caused the land to become arid and turtles to become extinct there, while new continental margins opened up by the climate change provided habitats for other species to evolve. The cladogram, from Nicholas Crawford and colleagues 2015, shows the internal phylogeny of the Testudines down to the level of
families Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideall ...
. The analysis by Thompson and colleagues in 2021 supports the same structure down to the family level.


Differences between the two suborders

Turtles are divided into two living suborders: Cryptodira and Pleurodira. The two groups differ in the way the neck is retracted for protection. Pleurodirans retract their neck to the side and in front of the shoulder girdles, whereas cryptodirans retract their neck backward into their shell. These motions are enabled by the morphology and arrangement of neck vertebrae. Sea turtles (which belong to Cryptodira) have mostly lost the ability to retract their heads. The adductor muscles in the lower jaw create a pulley-like system in both subgroups. However, the bones that the muscles articulate with differ. In Pleurodira, the pulley is formed with the
pterygoid bone The pterygoid is a paired bone forming part of the palate of many vertebrates, behind the palatine bone In anatomy, the palatine bones () are two irregular bones of the facial skeleton in many animal species, located above the uvula in the ...
s of the
palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sepa ...
, but in Cryptodira the pulley is formed with the otic capsule. Both systems help to vertically redirect the adductor muscles and maintain a powerful bite. A further difference between the suborders is the attachment of the pelvis. In Cryptodira, the pelvis is free, linked to the shell only by ligaments. In Pleurodira, the pelvis is sutured, joined with bony connections, to the carapace and to the plastron, creating a pair of large columns of bone at the back end of the turtle, linking the two parts of the shell.


Distribution and habitat

Turtles are widely distributed across the world's continents, oceans, and islands with terrestrial, fully aquatic, and semi-aquatic species. Sea turtles are mainly tropical and subtropical, but leatherbacks can be found in colder areas of the Atlantic and Pacific. Living Pleurodira all live in freshwater and are found only in the Southern Hemisphere. The Cryptodira include terrestrial, freshwater, and marine species, and these range more widely. The world regions richest in non-marine turtle species are the Amazon basin, the
Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United St ...
drainages of the United States, and parts of South and Southeast Asia. For turtles in colder climates, their distribution is limited by constraints on reproduction, which is reduced by long hibernations. North American species barely range above the southern Canadian border. Some turtles are found at high altitudes, for example, the species '' Terrapene ornata'' occurs up to in New Mexico. Conversely, the leatherback sea turtle can dive over . Species of the genus ''
Gopherus ''Gopherus'' is a genus of fossorial tortoises commonly referred to as gopher tortoises. The gopher tortoise is grouped with land tortoises that originated 60 million years ago, in North America. A genetic study has shown that their closest relat ...
'' can tolerate both below freezing and over in body temperature, though they are most active at .


Conservation

Among vertebrate orders, turtles are second only to primates in the percentage of threatened species. 360 modern species have existed since 1500 AD. Of these, 51–56% are considered threatened and 60% considered threatened or extinct. Turtles face many threats, including habitat destruction, harvesting for consumption, the pet trade,
light pollution Light pollution is the presence of unwanted, inappropriate, or excessive use of artificial lighting. In a descriptive sense, the term ''light pollution'' refers to the effects of any poorly implemented lighting, during the day or night. Light po ...
, and climate change. Asian species have a particularly high extinction risk, primarily due to their long-term unsustainable exploitation for food and medicine, and about 83% of Asia's non-marine turtle species are considered threatened. As of 2021, turtle extinction is progressing much faster than during the Cretaceous-Tertiary extinction. At this rate, all turtles could be extinct in a few centuries. Turtle
hatcheries A hatchery is a facility where eggs are hatched under artificial conditions, especially those of fish, poultry or even turtles. It may be used for ex-situ conservation purposes, i.e. to breed rare or endangered species under controlled co ...
can be set up when protection against flooding, erosion, predation, or heavy poaching is required. Chinese markets have sought to satisfy an increasing demand for turtle meat with farmed turtles. In 2007 it was estimated that over a thousand turtle farms operated in China. All the same, wild turtles continue to be caught and sent to market in large numbers, resulting in what conservationists have called "the Asian turtle crisis". In the words of the biologist George Amato, the hunting of turtles "vacuumed up entire species from areas in Southeast Asia", even as biologists still did not know how many species lived in the region. In 2000, all the Asian box turtles were placed on the
CITES CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...
list of endangered species. Harvesting wild turtles is legal in some American states, and there has been a growing demand for American turtles in China. The
Florida Fish and Wildlife Conservation Commission The Florida Fish and Wildlife Conservation Commission (FWC) is a Florida government agency founded in 1999 and headquartered in Tallahassee. It manages and regulates the state's fish and wildlife resources, and enforces related laws. Officers ar ...
estimated in 2008 that around 3,000 pounds of softshell turtles were exported weekly via
Tampa International Airport Tampa International Airport is an international airport west of Downtown Tampa, in Hillsborough County, Florida, United States. The airport is publicly owned by Hillsborough County Aviation Authority (HCAA)., effective December 30, 2021. The ...
. However, the great majority of turtles exported from the US between 2002 and 2005 were farmed. Large numbers of sea turtles are accidentally killed in longlines,
gillnets Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...
, and
trawling Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch different spec ...
nets as
bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...
. A 2010 study suggested that over 8 million had been killed between 1990 and 2008; the Eastern Pacific and the Mediterranean were identified as among the areas worst affected. Since the 1980s, the United States has required all shrimp trawlers to fit their nets with
turtle excluder device A turtle excluder device (TED) is a specialized device that allows a captured sea turtle to escape when caught in a fisherman's net. In particular, sea turtles can be caught when bottom trawling is used by the commercial shrimp fishing indus ...
s that prevent turtles from being entangled in the net and drowning. More locally, other human activities are affecting marine turtles. In Australia,
Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...
's
shark culling Shark culling is the deliberate killing of sharks by government authorities, usually in response to one or more shark attacks. The term "shark control" is often used by governments when referring to culls. Shark culling has been criticized by envi ...
program, which uses
shark nets A shark net is a submerged section of gillnets placed at beaches designed to intercept large marine animals including sharks, with the aim to reduce the likelihood of shark attacks on swimmers. Shark nets used are gillnets which is a wall of n ...
and
drum lines A drum line is an unmanned aquatic trap used to lure and capture large sharks using baited hooks. They are typically deployed near popular swimming beaches with the intention of reducing the number of sharks in the vicinity and therefore the prob ...
, has killed over 5,000 turtles as bycatch between 1962 and 2015; including 719 loggerhead turtles and 33 hawksbill sea turtles, which are listed as critically endangered. Native turtle populations can also be threatened by invasive ones. The central North American red-eared slider turtle has been listed among the " world's worst invasive species", pet turtle having been released globally. They appear to compete with native turtle species in eastern and western North America, Europe, and Japan.


Human uses


In culture

File:Kurmavatara (tortoise incarnation of Vishnu), from Garhwa, Allahabad District.jpg, alt=Photograph of temple sculpture in India, 4th-century sculpture of turtle avatar of
Vishnu Vishnu ( ; , ), also known as Narayana and Hari, is one of the principal deities of Hinduism. He is the supreme being within Vaishnavism, one of the major traditions within contemporary Hinduism. Vishnu is known as "The Preserver" within t ...
. Garhwa, India File:PSM V10 D562 The hindoo earth.jpg, alt=Lithograph drawing of world resting on 4 elephants standing on a giant turtle, World resting on four elephants on the back of the
World Turtle The World Turtle, also called the Cosmic Turtle or the World-bearing Turtle, is a mytheme of a giant turtle (or tortoise) supporting or containing the world. It occurs in Hindu mythology, Chinese mythology, and the mythologies of the indigenous ...
. Western depiction of "The Hindu Earth", 1877 File:Kangxi-Lugou-rebuilding-stele-3581.jpg, alt=Chinese funeral stone held up by a stone tortoise,
Bixi Bixi, or Bi Xi (), is a figure from Chinese mythology. One of the 9 sons of the Dragon King, he is depicted as a dragon with the shell of a turtle. Stone sculptures of Bixi have been used in Chinese culture for centuries as a decorative plinth ...
supporting
Kangxi Emperor The Kangxi Emperor (4 May 1654– 20 December 1722), also known by his temple name Emperor Shengzu of Qing, born Xuanye, was the third emperor of the Qing dynasty, and the second Qing emperor to rule over China proper, reigning from 1661 to 1 ...
's
stele A stele ( ),Anglicized plural steles ( ); Greek plural stelai ( ), from Greek , ''stēlē''. The Greek plural is written , ''stēlai'', but this is only rarely encountered in English. or occasionally stela (plural ''stelas'' or ''stelæ''), whe ...
,
Beijing } Beijing ( ; ; ), alternatively romanized as Peking ( ), is the capital of the People's Republic of China. It is the center of power and development of the country. Beijing is the world's most populous national capital city, with over 2 ...
, 1698 File:Alice par John Tenniel 34.png, alt=Children's book illustration with turtle figure standing on hind legs, The
Mock Turtle The Mock Turtle is a fictional character devised by Lewis Carroll from his popular 1865 book ''Alice's Adventures in Wonderland''. Its name is taken from a dish that was popular in the Victorian era, Victorian period, mock turtle soup. ''Alice's ...
in
Lewis Carroll Charles Lutwidge Dodgson (; 27 January 1832 – 14 January 1898), better known by his pen name Lewis Carroll, was an English author, poet and mathematician. His most notable works are '' Alice's Adventures in Wonderland'' (1865) and its seque ...
's 1865 ''
Alice's Adventures in Wonderland ''Alice's Adventures in Wonderland'' (commonly ''Alice in Wonderland'') is an 1865 English novel by Lewis Carroll. It details the story of a young girl named Alice who falls through a rabbit hole into a fantasy world of anthropomorphic creatu ...
'' File:The Turtle 1898 Manhattan Theatre poster.jpg, alt=Painting of a turtle standing on hind legs, with top hat and cane, on theatre poster, Poster for 1898 production of ''The Turtle'' at the Manhattan Theatre, Broadway File:Terrapin Shell Leg Rattles Worn by Lead Woman Dancer, Oconaluftee Village, NC. - NARA - 281630.jpg, alt=Photograph of cloth with four terrapin shell rattles to be tied around a dancer's leg, Terrapin shell leg rattles worn by lead Cherokee woman dancer, 20th century
Turtles have featured in human cultures across the world since ancient times. They are generally viewed positively despite not being "cuddly" or flashy; their association with the ancient times and old age have contributed to their endearing image. In
Hindu mythology Hindu mythology is the body of myths and literature attributed to, and espoused by, the adherents of the Hindu religion, found in Hindu texts such as the Vedic literature, epics like ''Mahabharata'' and ''Ramayana'', the Puranas, and regi ...
, the
World Turtle The World Turtle, also called the Cosmic Turtle or the World-bearing Turtle, is a mytheme of a giant turtle (or tortoise) supporting or containing the world. It occurs in Hindu mythology, Chinese mythology, and the mythologies of the indigenous ...
, named Kurma or Kacchapa, supports four elephants on his back; they, in turn, carry the weight of the whole world on their backs. The turtle is one of the ten
avatar Avatar (, ; ), is a concept within Hinduism that in Sanskrit literally means "descent". It signifies the material appearance or incarnation of a powerful deity, goddess or spirit on Earth. The relative verb to "alight, to make one's appearanc ...
s or incarnations of the god
Vishnu Vishnu ( ; , ), also known as Narayana and Hari, is one of the principal deities of Hinduism. He is the supreme being within Vaishnavism, one of the major traditions within contemporary Hinduism. Vishnu is known as "The Preserver" within t ...
. The
yoga Yoga (; sa, योग, lit=yoke' or 'union ) is a group of physical, mental, and spiritual practices or disciplines which originated in ancient India and aim to control (yoke) and still the mind, recognizing a detached witness-consciou ...
pose Kurmasana is named for the avatar. revised from American Academy of Religions conference, San Francisco, 19 November 2011. World Turtles are found in Native American cultures including the Algonquian,
Iroquois The Iroquois ( or ), officially the Haudenosaunee ( meaning "people of the longhouse"), are an Iroquoian-speaking confederacy of First Nations peoples in northeast North America/ Turtle Island. They were known during the colonial years to ...
, and
Lenape The Lenape (, , or Lenape , del, Lënapeyok) also called the Leni Lenape, Lenni Lenape and Delaware people, are an indigenous peoples of the Northeastern Woodlands, who live in the United States and Canada. Their historical territory includ ...
. They tell many versions of the
creation story A creation myth (or cosmogonic myth) is a symbolic narrative of how the world began and how people first came to inhabit it., "Creation myths are symbolic stories describing how the universe and its inhabitants came to be. Creation myths develop ...
of Turtle Island. One version has Muskrat pile up earth on Turtle's back, creating the continent of North America. An
Iroquois The Iroquois ( or ), officially the Haudenosaunee ( meaning "people of the longhouse"), are an Iroquoian-speaking confederacy of First Nations peoples in northeast North America/ Turtle Island. They were known during the colonial years to ...
version has the pregnant Sky Woman fall through a hole in the sky between a tree's roots, where she is caught by birds who land her safely on Turtle's back; the Earth grows around her. The turtle here is altruistic, but the world is a heavy burden, and the turtle sometimes shakes itself to relieve the load, causing earthquakes. A turtle was the symbol of the Ancient Mesopotamian god
Enki , image = Enki(Ea).jpg , caption = Detail of Enki from the Adda Seal, an ancient Akkadian cylinder seal dating to circa 2300 BC , deity_of = God of creation, intelligence, crafts, water, seawater, lakewater, fertility, semen, magic, mischief ...
from the 3rd millennium BCE onward. An ancient Greek
origin myth An origin myth is a myth that describes the origin of some feature of the natural or social world. One type of origin myth is the creation or cosmogonic myth, a story that describes the creation of the world. However, many cultures have sto ...
told that only the tortoise refused the invitation of the gods
Zeus Zeus or , , ; grc, Δῐός, ''Diós'', label=genitive Boeotian Aeolic and Laconian grc-dor, Δεύς, Deús ; grc, Δέος, ''Déos'', label=genitive el, Δίας, ''Días'' () is the sky and thunder god in ancient Greek religion, ...
and
Hera In ancient Greek religion, Hera (; grc-gre, Ἥρα, Hḗrā; grc, Ἥρη, Hḗrē, label=none in Ionic and Homeric Greek) is the goddess of marriage, women and family, and the protector of women during childbirth. In Greek mythology, she ...
to their wedding, as it preferred to stay at home. Zeus then ordered it to carry its house with it, ever after. Another of their gods,
Hermes Hermes (; grc-gre, Ἑρμῆς) is an Olympian deity in ancient Greek religion and mythology. Hermes is considered the herald of the gods. He is also considered the protector of human heralds, travellers, thieves, merchants, and orator ...
, invented a seven-stringed
lyre The lyre () is a stringed musical instrument that is classified by Hornbostel–Sachs as a member of the lute-family of instruments. In organology, a lyre is considered a yoke lute, since it is a lute in which the strings are attached to a yoke ...
made with the shell of a tortoise. In the
Shang dynasty The Shang dynasty (), also known as the Yin dynasty (), was a Chinese royal dynasty founded by Tang of Shang (Cheng Tang) that ruled in the Yellow River valley in the second millennium BC, traditionally succeeding the Xia dynasty and ...
Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of v ...
practice of
plastromancy Oracle bones () are pieces of ox scapula and turtle plastron, which were used for pyromancy – a form of divination – in ancient China, mainly during the late Shang dynasty. ''Scapulimancy'' is the correct term if ox scapulae were used for th ...
, dating back to 1200 BCE, oracles were obtained by inscribing questions on turtle plastrons using the oldest known form of Chinese characters, burning the plastron, and interpreting the resulting cracks. Later, the turtle was one of the four sacred animals in Confucianism, while in the
Han period The Han dynasty (, ; ) was an imperial dynasty of China (202 BC – 9 AD, 25–220 AD), established by Liu Bang (Emperor Gao) and ruled by the House of Liu. The dynasty was preceded by the short-lived Qin dynasty (221–207 BC) and a war ...
,
stele A stele ( ),Anglicized plural steles ( ); Greek plural stelai ( ), from Greek , ''stēlē''. The Greek plural is written , ''stēlai'', but this is only rarely encountered in English. or occasionally stela (plural ''stelas'' or ''stelæ''), whe ...
s were mounted on top of stone turtles, later linked with
Bixi Bixi, or Bi Xi (), is a figure from Chinese mythology. One of the 9 sons of the Dragon King, he is depicted as a dragon with the shell of a turtle. Stone sculptures of Bixi have been used in Chinese culture for centuries as a decorative plinth ...
, the turtle-shelled son of the Dragon King. Marine turtles feature significantly in
Australian Aboriginal Aboriginal Australians are the various Indigenous peoples of the Australian mainland and many of its islands, such as Tasmania, Fraser Island, Hinchinbrook Island, the Tiwi Islands, and Groote Eylandt, but excluding the Torres Strait Islands ...
art. The army of Ancient Rome used the ("tortoise") formation where soldiers would form a shield wall for protection. In
Aesop's Fables Aesop's Fables, or the Aesopica, is a collection of fables credited to Aesop, a slave and storyteller believed to have lived in ancient Greece between 620 and 564 BCE. Of diverse origins, the stories associated with his name have descended to m ...
, "
The Tortoise and the Hare "The Tortoise and the Hare" is one of Aesop's Fables and is numbered 226 in the Perry Index. The account of a race between unequal partners has attracted conflicting interpretations. The fable itself is a variant of a common folktale theme in wh ...
" tells how an unequal race may be won by the slower partner.
Lewis Carroll Charles Lutwidge Dodgson (; 27 January 1832 – 14 January 1898), better known by his pen name Lewis Carroll, was an English author, poet and mathematician. His most notable works are '' Alice's Adventures in Wonderland'' (1865) and its seque ...
's 1865 ''
Alice's Adventures in Wonderland ''Alice's Adventures in Wonderland'' (commonly ''Alice in Wonderland'') is an 1865 English novel by Lewis Carroll. It details the story of a young girl named Alice who falls through a rabbit hole into a fantasy world of anthropomorphic creatu ...
'' features a
Mock Turtle The Mock Turtle is a fictional character devised by Lewis Carroll from his popular 1865 book ''Alice's Adventures in Wonderland''. Its name is taken from a dish that was popular in the Victorian era, Victorian period, mock turtle soup. ''Alice's ...
, named for a soup meant to imitate the expensive soup made from real turtle meat. In 1896, the French playwright Léon Gandillot wrote a comedy in three acts named that was "a Parisian sensation" in its run in France, and came to the
Manhattan Theatre The Manhattan Theatre was located at 102 West 33rd Street in Midtown Manhattan, New York City, directly across from Greeley Square at Sixth Avenue and 33rd Street. The 1,100-seat theatre opened in 1875 as the Eagle Theatre, and was renamed the ...
, Broadway, New York, in 1898 as ''The Turtle''. A "cosmic turtle" and the island motif reappear in
Gary Snyder Gary Snyder (born May 8, 1930) is an American poet, essayist, lecturer, and environmental activist. His early poetry has been associated with the Beat Generation and the San Francisco Renaissance and he has been described as the "poet laureate of ...
's 1974 novel '' Turtle Island'', and again in
Terry Pratchett Sir Terence David John Pratchett (28 April 1948 – 12 March 2015) was an English humourist, satirist, and author of fantasy novels, especially comical works. He is best known for his ''Discworld'' series of 41 novels. Pratchett's first no ...
's ''
Discworld ''Discworld'' is a comic fantasy"Humorous Fantasy" in David Pringle, ed., ''The Ultimate Encyclopedia of Fantasy'' (pp.31-33). London, Carlton,2006. book series written by the English author Terry Pratchett, set on the Discworld, a flat pla ...
'' series as Great A'Tuin, starting with the 1983 novel ''
The Colour of Magic ''The Colour of Magic'' is a 1983 fantasy comedy novel by Terry Pratchett, and is the first book of the ''Discworld'' series. The first printing of the British edition consisted of only 506 copies. Pratchett has described it as "an attempt to ...
''. It is supposedly of the species ''Chelys galactica'', the galactic turtle, complete with four elephants on its back to support Discworld. Turtles have been featured in comic books and animations such as the 1984
Teenage Mutant Ninja Turtles ''Teenage Mutant Ninja Turtles'' is an American media franchise created by the comic book artists Kevin Eastman and Peter Laird. It follows Leonardo (Teenage Mutant Ninja Turtles), Leonardo, Michelangelo (Teenage Mutant Ninja Turtles), Miche ...
.


As pets

Some turtles, particularly small terrestrial and freshwater species, are kept as
pet A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive appearances, intelligence, ...
s. The demand for pet turtles increased in the 1950s, with the US being the main supplier, particularly of farm-bred red-eared sliders. The popularity for exotic pets has led to an increase in illegal
wildlife trafficking Wildlife smuggling or trafficking involves the illegal gathering, transportation, and distribution of animals and their derivatives. This can be done either internationally or domestically. Estimates of the money generated by wildlife smuggling ...
. Around 21% of the value of live animal trade is in reptiles, and turtles are among the more popularly traded species. Poor husbandry of tortoises can cause chronic
rhinitis Rhinitis, also known as coryza, is irritation and inflammation of the mucous membrane inside the nose. Common symptoms are a stuffy nose, runny nose, sneezing, and post-nasal drip. The inflammation is caused by viruses, bacteria, irritant ...
(nasal swelling), overgrown beaks,
hyperparathyroidism Hyperparathyroidism is an increase in parathyroid hormone (PTH) levels in the blood. This occurs from a disorder either within the parathyroid glands ( primary hyperparathyroidism) or as response to external stimuli ( secondary hyperparathyroid ...
(which softens their skeleton),
constipation Constipation is a bowel dysfunction that makes bowel movements infrequent or hard to pass. The stool is often hard and dry. Other symptoms may include abdominal pain, bloating, and feeling as if one has not completely passed the bowel movement ...
, various reproductive problems, and injuries from dogs. In the early 20th century, people in the United States have organized and gambled on turtle races.


As food and other uses

The flesh of captured wild turtles continues to be eaten in Asian cultures, while
turtle soup Turtle soup, also known as Terrapin soup, is a soup or stew made from the meat of turtles. Differing versions of the soup exist in some cultures and are viewed as a delicacy. Versions China In China, and in several countries in Southeast Asi ...
was once a popular dish in
English cuisine English cuisine encompasses the cooking styles, traditions and recipes associated with England. It has distinctive attributes of its own, but also shares much with wider British cuisine, partly through the importation of ingredients and ideas ...
. Gopher tortoise stew has been popular with some groups in Florida. The supposed aphrodisiac or medicinal properties of turtle eggs created a large trade for them in Southeast Asia. Hard-shell turtle plastrons and soft-shell carapaces are widely used in
traditional Chinese medicine Traditional Chinese medicine (TCM) is an alternative medical practice drawn from traditional medicine in China. It has been described as "fraught with pseudoscience", with the majority of its treatments having no logical mechanism of action ...
;
Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the northeast ...
imported nearly 200 metric tons of hard-shells from its neighbors yearly from 1999 to 2008. A popular medicinal preparation based on herbs and turtle shells is ''
guilinggao ''Guilinggao'' (), also known as tortoise jelly (though not technically correct) or turtle powder, is a jelly-like Chinese medicine, also sold as a dessert. It was traditionally made from the ''gao'', or paste of the plastron (bottom shell) fr ...
'' jelly. The substance
tortoiseshell Tortoiseshell or tortoise shell is a material produced from the shells of the larger species of tortoise and turtle, mainly the hawksbill sea turtle, which is a critically endangered species according to the IUCN Red List largely because of its ...
, usually from the hawksbill turtle, has been used for centuries to make jewelry, tools, and ornaments around the Western Pacific. Hawksbills have accordingly been hunted for their shells. The trading of tortoiseshell was internationally banned in 1977 by CITES. Some cultures have used turtle shells to make music: Native American
shaman Shamanism is a religious practice that involves a practitioner (shaman) interacting with what they believe to be a spirit world through altered states of consciousness, such as trance. The goal of this is usually to direct spirits or spiri ...
s made them into ceremonial rattles, while
Aztec The Aztecs () were a Mesoamerican culture that flourished in central Mexico in the post-classic period from 1300 to 1521. The Aztec people included different ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl ...
s,
Maya Maya may refer to: Civilizations * Maya peoples, of southern Mexico and northern Central America ** Maya civilization, the historical civilization of the Maya peoples ** Maya language, the languages of the Maya peoples * Maya (Ethiopia), a populat ...
s, and
Mixtec The Mixtecs (), or Mixtecos, are indigenous Mesoamerican peoples of Mexico inhabiting the region known as La Mixteca of Oaxaca and Puebla as well as La Montaña Region and Costa Chica Regions of the state of Guerrero. The Mixtec Culture ...
s made ' drums. File:StateLibQld 2 395489 Catching turtles, wood engraving, 1875.jpg, Catching turtles in Australia, 1875, alt=Historic engraving of men catching turtles on a beach File:TurtleSeafood.jpg, Turtles on sale as food in Canada, 2007, alt=photo of turtles on sale as food in a shop File:Turtle plastrons as TCM in Xi'an market.jpg, Turtle plastrons for traditional Chinese medicine, alt=Photograph of a box of turtle plastrons in a market File:Peigne en écaille.jpg, A tortoiseshell comb; the material was expensive and decorative, and widely used for small items., alt=Photograph of a decoratively ridged comb made of tortoiseshell File:Sheldonbasking.JPG, A pet red-eared slider basking on a floating platform under a sun lamp, alt=Photograph of a pet turtle in a terrarium


See also

* World Turtle Day


References


Citations


Cited sources

* * *


External links


Turtle Survival Alliance

Turtle Conservancy

Symposium on Turtle Evolution
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Turtles Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked t ...
Articles containing video clips Kimmeridgian first appearances Extant Late Jurassic first appearances Turtle taxonomy