crepuscular
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In zoology, a crepuscular
animal Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage ...
is one that is active primarily during the
twilight Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this i ...
period, being
matutinal Matutinal, matinal (in entomological writings), and matutine are terms used in the life sciences to indicate something of, relating to, or occurring in the early morning. The term may describe crepuscular animals that are significantly active ...
, vespertine, or both. This is distinguished from diurnal and
nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sen ...
behavior, where an animal is active during the hours of
daylight Daylight is the combination of all direct and indirect sunlight during the daytime. This includes direct sunlight, diffuse sky radiation, and (often) both of these reflected by Earth and terrestrial objects, like landforms and buildings. Sunlig ...
and of
darkness Darkness, the direct opposite of lightness, is defined as a lack of illumination, an absence of visible light, or a surface that absorbs light, such as black or brown. Human vision is unable to distinguish colors in conditions of very low l ...
, respectively. Some crepuscular animals may also be active by moonlight or during an
overcast Overcast or overcast weather, as defined by the World Meteorological Organization, is the meteorological condition of clouds obscuring at least 95% of the sky. However, the total cloud cover must not be entirely due to obscuring phenomena near ...
day.
Matutinal Matutinal, matinal (in entomological writings), and matutine are terms used in the life sciences to indicate something of, relating to, or occurring in the early morning. The term may describe crepuscular animals that are significantly active ...
animals are active only before
sunrise Sunrise (or sunup) is the moment when the upper rim of the Sun appears on the horizon in the morning. The term can also refer to the entire process of the solar disk crossing the horizon and its accompanying atmospheric effects. Terminology ...
, and vespertine only after
sunset Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As viewed from everywhere on Earth (except the North and South poles), the equinox Sun sets due west at the moment of both the sp ...
. A number of factors impact the time of day an animal is active.
Predators Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...
hunt when their prey is available, and prey try to avoid the times when their principal predators are at large. The temperature at midday may be too high or at night too low. Some creatures may adjust their activities depending on local competition.


Etymology and usage

The word ''crepuscular'' derives from the Latin '' crepusculum'' ("twilight"). Its sense accordingly differs from diurnal and
nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sen ...
behavior, which respectively peak during hours of daylight and darkness. The distinction is not absolute however, because crepuscular animals may also be active on a bright moonlit night or on a dull day. Some animals casually described as nocturnal are in fact crepuscular. Special classes of crepuscular behaviour include
matutinal Matutinal, matinal (in entomological writings), and matutine are terms used in the life sciences to indicate something of, relating to, or occurring in the early morning. The term may describe crepuscular animals that are significantly active ...
(or "matinal", animals active only in the dawn) and vespertine (only in the dusk). Those active during both times are said to have a bimodal activity pattern.


Adaptive relevance

The various patterns of activity are thought to be mainly
antipredator adaptation Anti-predator adaptations are mechanisms developed through evolution that assist prey organisms in their constant struggle against predators. Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by av ...
s, though some could equally well be predatory
adaptation In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the ...
s. Many predators
forage Forage is a plant material (mainly plant leaves and stems) eaten by grazing livestock. Historically, the term ''forage'' has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used ...
most intensively at night, whereas others are active at midday and see best in full sun. Thus, the crepuscular habit may both reduce predation pressure, thereby increasing the crepuscular populations, and in consequence offer better foraging opportunities to predators that increasingly focus their attention on crepuscular prey until a new balance is struck. Such shifting states of balance are often found in ecology. Some predatory species adjust their habits in response to competition from other predators. For example, the subspecies of
short-eared owl The short-eared owl (''Asio flammeus'') is a widespread grassland species in the family Strigidae. Owls belonging to genus '' Asio'' are known as the eared owls, as they have tufts of feathers resembling mammalian ears. These "ear" tufts may o ...
that lives on the
Galápagos Islands The Galápagos Islands ( Spanish: , , ) are an archipelago of volcanic islands. They are distributed on each side of the equator in the Pacific Ocean, surrounding the centre of the Western Hemisphere, and are part of the Republic of Ecuador ...
is normally active during the day, but on islands like Santa Cruz that are home to the Galapagos hawk, the owl is crepuscular. Apart from the relevance to predation, crepuscular activity in hot regions also may be the most effective way of avoiding heat stress while capitalizing on available light. Crepuscular flight activity is preferred by some animals, such as the walnut twig beetle, due to warmer temperatures, moderate wind speeds, and low barometric pressure. Crepuscular activity can be influenced by the
lunar cycle Concerning the lunar month of ~29.53 days as viewed from Earth, the lunar phase or Moon phase is the shape of the Moon's directly sunlit portion, which can be expressed quantitatively using areas or angles, or described qualitatively using the t ...
due to the change in nocturnal light. This creates changes in animal
sleep Sleep is a sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefulness by a ...
,
reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organisms – " offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual ...
, and
foraging Foraging is searching for wild food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce. Foraging theory is a branch of behavioral ecology that studies the foraging behav ...
behaviours, often becoming less active during periods of low light.


Migration

Animal patterns of activity sometimes change during
migration Migration, migratory, or migrate may refer to: Human migration * Human migration, physical movement by humans from one region to another ** International migration, when peoples cross state boundaries and stay in the host state for some minimum l ...
due to changes in environmental conditions.
Mule deer The mule deer (''Odocoileus hemionus'') is a deer indigenous to western North America; it is named for its ears, which are large like those of the mule. Two subspecies of mule deer are grouped into the black-tailed deer. Unlike the related w ...
are crepuscular, but they are only active at
sunset Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As viewed from everywhere on Earth (except the North and South poles), the equinox Sun sets due west at the moment of both the sp ...
before and during migration. However, in the spring they are only active at
sunrise Sunrise (or sunup) is the moment when the upper rim of the Sun appears on the horizon in the morning. The term can also refer to the entire process of the solar disk crossing the horizon and its accompanying atmospheric effects. Terminology ...
because the
snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout ...
is at its hardest so it is easier for the deer to move without sinking in the snow. During migration, some
types Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...
of
swallow The swallows, martins, and saw-wings, or Hirundinidae, are a family of passerine songbirds found around the world on all continents, including occasionally in Antarctica. Highly adapted to aerial feeding, they have a distinctive appearance. Th ...
are active primarily during daytime hours with some activity during twilight hours.


Human impact on crepuscular behaviour

Crepuscular animal activity is affected by human activity. Crepuscular animals are less likely to participate in typical foraging or reproductive behaviors and deal with increased stress and mortality rates when humans are present. Animals may also change their usual activity patterns in response to the presence of humans. For example, Asian black bears may avoid areas with high human activity during the day, but go to these locations during twilight or nighttime hours.
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 ...
impacts crepuscular behaviour because it mimics natural light conditions, leading crepuscular animals to behave as they would on nights with more moonlight.


Occurrence of crepuscular behaviour

Many familiar
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 ...
species are crepuscular, including some
bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most b ...
s,
hamster Hamsters are rodents (order Rodentia) belonging to the subfamily Cricetinae, which contains 19 species classified in seven genera.Fox, Sue. 2006. ''Hamsters''. T.F.H. Publications Inc. They have become established as popular small pets. Th ...
s, housecats, stray dogs,
rabbit Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (which also contains the hares) of the order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' includes the European rabbit ...
s,
ferret The ferret (''Mustela furo'') is a small, domesticated species belonging to the family Mustelidae. The ferret is most likely a domesticated form of the wild European polecat (''Mustela putorius''), evidenced by their interfertility. Other mus ...
s, and
rat Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include ''Neotoma'' ( pack rats), '' Bandicota'' (bandicoo ...
s. Other crepuscular mammals include jaguars,
ocelot The ocelot (''Leopardus pardalis'') is a medium-sized spotted wild cat that reaches at the shoulders and weighs between on average. It was first described by Carl Linnaeus in 1758. Two subspecies are recognized. It is native to the southwe ...
s,
bobcat The bobcat (''Lynx rufus''), also known as the red lynx, is a medium-sized cat native to North America. It ranges from southern Canada through most of the contiguous United States to Oaxaca in Mexico. It is listed as Least Concern on the ...
s,
serval The serval (''Leptailurus serval'') is a wild cat native to Africa. It is widespread in sub-Saharan countries, except rainforest regions. Across its range, it occurs in protected areas, and hunting it is either prohibited or regulated in ran ...
s,
strepsirrhine Strepsirrhini or Strepsirhini (; ) is a suborder of primates that includes the lemuriform primates, which consist of the lemurs of Madagascar, galagos ("bushbabies") and pottos from Africa, and the lorises from India and southeast Asia. ...
s,
red panda The red panda (''Ailurus fulgens''), also known as the lesser panda, is a small mammal native to the eastern Himalayas and southwestern China. It has dense reddish-brown fur with a black belly and legs, white-lined ears, a mostly white muzz ...
s,
bear Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the Nort ...
s,
deer Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the reindeer ...
, moose,
sitatunga The sitatunga or marshbuck (''Tragelaphus spekii'') is a swamp-dwelling antelope found throughout central Africa, centering on the Democratic Republic of the Congo, the Republic of the Congo, Cameroon, parts of Southern Sudan, Equatorial Guinea, ...
,
capybara The capybaraAlso called capivara (in Brazil), capiguara (in Bolivia), chigüire, chigüiro, or fercho (in Colombia and Venezuela), carpincho (in Argentina, Paraguay and Uruguay) and ronsoco (in Peru). or greater capybara (''Hydrochoerus hydro ...
s,
chinchilla Chinchillas are either of two species ('' Chinchilla chinchilla'' and '' Chinchilla lanigera'') of crepuscular rodents of the parvorder Caviomorpha. They are slightly larger and more robust than ground squirrels, and are native to the Andes ...
s, the common
mouse A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus ...
,
skunk Skunks are mammals in the family Mephitidae. They are known for their ability to spray a liquid with a strong, unpleasant scent from their anal glands. Different species of skunk vary in appearance from black-and-white to brown, cream or gi ...
s,
squirrel Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrels. Squ ...
s,
fox Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or ''brush''). Twelve s ...
es,
wombat Wombats are short-legged, muscular quadrupedal marsupials that are native to Australia. They are about in length with small, stubby tails and weigh between . All three of the extant species are members of the family Vombatidae. They are adap ...
s, wallabies,
quoll Quolls (; genus ''Dasyurus'') are carnivorous marsupials native to Australia and New Guinea. They are primarily nocturnal and spend most of the day in a den. Of the six species of quoll, four are found in Australia and two in New Guinea. Ano ...
s,
possums Possum may refer to: Animals * Phalangeriformes, or possums, any of a number of arboreal marsupial species native to Australia, New Guinea, and Sulawesi ** Common brushtail possum (''Trichosurus vulpecula''), a common possum in Australian urban ...
and marsupial gliders,
tenrec A tenrec is any species of mammal within the afrotherian family Tenrecidae endemic to Madagascar. Tenrecs are wildly diverse; as a result of convergent evolution some resemble hedgehogs, shrews, opossums, rats, and mice. They occupy aquatic ...
s, and spotted hyenas. Snakes, lizards, and
frogs A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" '' Triadobatrachus'' ...
, especially those in desert environments, may be crepuscular. Crepuscular birds include the
common nighthawk The common nighthawk (''Chordeiles minor'') is a medium-sized crepuscular or nocturnal bird of the Americas within the nightjar family, whose presence and identity are best revealed by its vocalization. Typically dark (gray, black and brown), di ...
,
barn owl The barn owl (''Tyto alba'') is the most widely distributed species of owl in the world and one of the most widespread of all species of birds, being found almost everywhere except for the polar and desert regions, Asia north of the Himalaya ...
,
owlet-nightjar Owlet-nightjars are small crepuscular birds related to the nightjars and frogmouths. Most are native to New Guinea, but some species extend to Australia, the Moluccas, and New Caledonia. A flightless species from New Zealand is extinct. Ther ...
, chimney swift, American woodcock, spotted crake, white-breasted waterhen, European nightjars, and common buzzards. Many
moth Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of ...
s,
beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describe ...
s,
flies Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...
, and other insects are crepuscular and vespertine.


See also

*
Cathemeral Cathemerality, sometimes called metaturnality, is an organismal activity pattern of irregular intervals during the day or night in which food is acquired, socializing with other organisms occurs, and any other activities necessary for livelihood ar ...
*
Crypsis In ecology, crypsis is the ability of an animal or a plant to avoid observation or detection by other animals. It may be a predation strategy or an antipredator adaptation. Methods include camouflage, nocturnality, subterranean lifestyle and ...
*
Diurnality Diurnality is a form of plant and animal behavior characterized by activity during daytime, with a period of sleeping or other inactivity at night. The common adjective used for daytime activity is "diurnal". The timing of activity by an animal ...
*
Nocturnality Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sen ...


References

{{Light Ethology Ethology Night de:Temporale Spezialisten