The American toad (''Anaxyrus americanus'')
is a common species of
toad
Toad (also known as a hoptoad) is a common name for certain frogs, especially of the family Bufonidae, that are characterized by dry, leathery skin, short legs, and large bumps covering the parotoid glands.
In popular culture (folk taxonomy ...
found throughout
Canada
Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
and the eastern
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
. It is divided into three subspecies: the eastern American toad (''A. a. americanus''), the dwarf American toad (''A. a. charlesmithi'') and the rare
Hudson Bay toad (''A. a. copei''). Recent taxonomic treatments place this species in the genus ''
Anaxyrus'' instead of ''
Bufo''.
Eggs
A. americanus eggs are bicolored. They are often a roughly equal mixture of a black or brown with white or cream. The eggs are deposited in two long ropes that have been recorded to transcend 60 m in length. Single egg diameter ranges from 0.1 cm to 0.2 cm.
Tadpoles
The American toad lays between 2,000-20,000 eggs in two strings which hatch in 3-12 days. The hatched tadpole
A tadpole or polliwog (also spelled pollywog) is the Larva, larval stage in the biological life cycle of an amphibian. Most tadpoles are fully Aquatic animal, aquatic, though some species of amphibians have tadpoles that are terrestrial animal, ...
s, while very small, are recognizable by their skinny tails in relation to the size of their round black bodies. They reach adulthood in 50–65 days. When metamorphosis is complete, the "toadlets" may stay in the water for a short period of time before transitioning to be mostly land based. Often times, groups of tadpoles reach the ''toadlet'' stage at once and a begin a mass migration to higher ground. Typically, toadlets migrate to shaded areas in the mid-range and upland forests that border the marshes where they were bred. Toadlets can be observed eating microscopic bugs in their roaming ground between various vegetation; they are also known to eat ants, spiders, slugs and worms. Studies have shown that they have a mutualistic relationship with '' Chlorogonium'' algae, which makes tadpoles develop faster than normal. Leaf litter from invasive plants like autumn olive or purple loosestrife in the larval nursery can increase the burden of trematode
Trematoda is a Class (biology), class of flatworms known as trematodes, and commonly as flukes. They are obligate parasite, obligate Endoparasites, internal parasites with a complex biological life cycle, life cycle requiring at least two Host ( ...
parasite infestation among tadpoles. This is possibly mediated by faster development of tadpoles in these aquatic environments than in nurseries with leaves of native black huckleberry or swamp loosestrife.
Tadpoles have several mechanisms to reduce predation. They avoid predators by swimming in very shallow water often with thick grass vegetation and by swimming close together in schools during the day. Tadpoles also produce toxic chemicals in their skin that discourage some predation. Fish have been reported to die after consuming one tadpole; however, most fish quickly learn to avoid eating American toad tadpoles.
Biogeography
Based on DNA sequence comparisons, ''Anaxyrus americanus'' and other North American species of ''Anaxyrus'' are thought to be descended from an invasion of toads from South America prior to the formation of the Isthmus of Panama
The Isthmus of Panama, historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North America, North and South America. The country of Panama is located on the i ...
land bridge, presumably by means of rafting
Rafting and whitewater rafting are recreational outdoor activities which use an inflatable raft to navigate a river or other body of water. This is often done on whitewater or different degrees of rough water. Dealing with risk is often a ...
.
Subspecies
Races tend to hybridize with '' Anaxyrus woodhousii'' in their overlapping ranges.
Eastern American toad
The eastern American toad (''A. a. americanus'') is a medium-sized toad usually ranging in size from ; the record length for an eastern American toad is . The color and pattern is somewhat variable, especially for the females. Skin color can change depending on habitat colors, humidity, stress, and temperature. Color changes range from yellow to brown to black, from solid colors to speckled. Their breeding habits are very similar to '' Anaxyrus fowleri''. The call or voice of a breeding male is a high trill that lasts between 6–30 seconds[ and sounds similar to a ringing telephone. Males call for an average of 6-7 nights during their breeding period. Females show preference for call efforts (rate × duration), but not call frequency. They hibernate during the winter. The eastern American toad has spots that contain only one to two warts. It also has enlarged warts on the tibia or lower leg below the knee. While the belly is usually spotted, in some areas many are, and it is generally more so on the forward half (in some rare individuals there may be few or no spots). This subspecies of the American toad has no or very little markings on it. The spades on the back legs are blackish. Some toads of this subspecies have a more pervasive red and deep brown color, many with red warts on their bodies. Also eastern American toads have parotoid glands that are the same color as the surrounding skin. The glands don't usually have any patterning on them.
Other species that may be confused with the eastern American toad are Fowler's toad, which has three or more warts in the largest dark spots, and in the far west of its range woodhouse's toad. Fowler's toad can be especially difficult to identify in comparison to the eastern American toad but one difference is that it never has a spotted belly and both cranial crests touch the ]parotoid gland
The parotoid gland (alternatively, paratoid gland) is an external skin gland on the back, neck, and shoulder of some frogs (especially toads), and salamanders. It can secrete a number of milky alkaloid substances (depending on the species) known ...
s. Also, Fowler's toads are very fast hoppers (bursts of 5–10 fast hops) in comparison to Eastern toads lethargic, casual hopping and walking locomotion. In the eastern American toad these crests almost never touch the parotoid glands, which secrete bufotoxin
Bufotoxins are a family of toxic steroid lactones or substituted Substituted tryptamine, tryptamines of which some are toxic. They occur in the parotoid glands, skin, and poison of many toads (True toad, Bufonidae family) and other amphibians, an ...
, a poisonous substance meant to make the toad unpalatable to potential predators. Bufotoxin
Bufotoxins are a family of toxic steroid lactones or substituted Substituted tryptamine, tryptamines of which some are toxic. They occur in the parotoid glands, skin, and poison of many toads (True toad, Bufonidae family) and other amphibians, an ...
is a mild poison in comparison to that of other poisonous toads and frogs, but it can irritate human eyes and mucous membranes and is dangerous to smaller animals (such as dogs) when ingested.
American toads require a semi-permanent freshwater pond or pool with shallow water in which to breed, to gather their water supplies in times of drought or as a routine,[ and for their early development. They also require dense patches of vegetation, for cover and hunting grounds. Given these two things and a supply of insects for food, American toads can live almost everywhere, ranging from forests to flat grassland. Females when caught are silent and easily tamed, adapting to terrarium life readily, while the smaller males are readily communicative. The smaller males do not adapt well to terrarium life and should be released after a few days of observation. Adult toads are mostly nocturnal, although juveniles are often abroad by day. When it rains, these toads will become active and can be observed eating robustly worms and insects leaving their burrows and walking in front of an opportunist toad. These toads are 'creatures of habit' once they have a certain area they prefer to live within... an acre of wooded forest with water in proximity for soaking, a home with cool ledges and window wells; they commonly seek cover in burrows, under boardwalks, flat stones, boards, logs, wood piles, or other cover. When cold weather comes, these toads dig backwards and bury themselves in the dirt of their summer homes, or they may choose another site in which to hibernate.][ Their diet includes crickets, mealworms, ]earthworm
An earthworm is a soil-dwelling terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (or subclass, depending on the author) Oligochaeta. In classical systems, they we ...
s, ant
Ants are Eusociality, eusocial insects of the Family (biology), family Formicidae and, along with the related wasps and bees, belong to the Taxonomy (biology), order Hymenoptera. Ants evolved from Vespoidea, vespoid wasp ancestors in the Cre ...
s, spider
Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...
s, slug
Slug, or land slug, is a common name for any apparently shell-less Terrestrial mollusc, terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced ...
s, centipede
Centipedes (from Neo-Latin , "hundred", and Latin , "foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', "lip", and Neo-Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, ...
s, moth
Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyletic with respect to butterflies (s ...
s, and other small invertebrates. Some of these toads have been known to live over 30 years and currently a female specimen (over 13 centimeters long) is living healthily into her late 30s. Another female toad of 17 centimeters is known to have existed in Wisconsin from Washington Island on Lake Michigan.
The eastern American toad may be confused with the Canadian toad in the area where they overlap, but the cranial crests in the American toad do not join to form a raised "boss" (bump) like they do in the Canadian toad. Its range also overlaps with the southern toad's, but in this species the cranial crests form two unique knobs.
Dwarf American toad
The dwarf American toad (''A. a. charlesmithi''), is a smaller version of the American toad, which reaches lengths of about , is generally a dark reddish color ranging to light red in some specimens in isolated populations. The spots on the back are reduced or absent, and when present they contain a few small red warts and a black ring around it like in the normal American toad. The warts are always darker than the skin of the toad. Some specimens have a white dorsal line in the middle of their backs. The ventral surface or belly is usually cream colored with a few dark spots in the breast area. This subspecies can be distinguished from the above-mentioned species in the same manner as for the eastern American toad. The southwestern portion of the Dwarf American toad's range overlaps with that of the Gulf Coast toad
The Gulf Coast toad (''Incilius valliceps'') is a species of toad native to eastern and southeastern Mexico and Central America as far south as Costa Rica.
Description
The Gulf Coast toad is a medium-sized toad species, ranging from in leng ...
. The latter species is distinguished by the presence of a dark lateral stripe as well as a deep "valley" between its prominent cranial crests. It eats mainly spiders, worms and small insects.
Hudson Bay toad
The Hudson Bay toad (''A. a. copei'') is a rare Canadian subspecies of ''A. americanus''. This subspecies of the American toad has been seen in the northern parts of Ontario where there are a few isolated populations. These northern dwarf toads mostly have the red coloring on the sides of their bodies and have an unusually high number of warts for the subspecies. Interbreeding with eastern American toads caused this subspecies to lose the red coloring on their backs.
Inbreeding avoidance
Toads display breeding site fidelity, as do many other amphibians. Individuals that return to natal ponds to breed will likely encounter siblings as potential mates. Although incest
Incest ( ) is sexual intercourse, sex between kinship, close relatives, for example a brother, sister, or parent. This typically includes sexual activity between people in consanguinity (blood relations), and sometimes those related by lineag ...
is possible, ''Anaxyrus americanus'' siblings rarely mate. These toads likely recognize and actively avoid close kins as mates. Advertisement vocalizations by males appear to serve as cues by which females recognize their kin.[
]
Gallery
File:Newly metamorphosed American Toad.png, Newly metamorphosed American Toad (~5mm) at confluence of Keay Brook, Berwick, ME and the Salmon Falls River.
File:Smallamericantoad.JPG, Approximately one week into adult cycle, shown in comparison to an adult female human hand
File:Toadfells.jpg, Eastern American toad, seen from behind, shows characteristic markings and "warts"
File:Bufo americanus Toad.JPG, Closeup of the Eastern American toad
File:Red Bufo americanus.JPG, Young American toad
File:Eastern american toad.jpg, Front view of Eastern American toad
File:Bufo americanus Side.JPG, Side view of camouflaged ''A. americanus''
File:Eastern American toad (Sudden Tract).jpg, Eastern American toad (''A. a. americanus''), North Dumfries, Ontario
File:American toad shedding skin.JPG, American toad eating its skin as it sheds
File:American Toad singing.jpg, American toad chirp - mating call
File:American Toad 8638.jpg, American toad feeding time
File:American toad named "Betty".png, 5 year old female American toad.
File:Toad Under Board.jpg, A closeup of an Eastern American toad seen in Tennessee.
See also
* European toad
* European green toad
* Japanese toad
References
External links
B. americanus
at the United States Geological Survey
The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...
site
USDA – ''Bufo americanus''
– ''United States Department of Agriculture Integrated Taxonomic Information System
The Integrated Taxonomic Information System (ITIS) is an American partnership of federal agencies designed to provide consistent and reliable information on the taxonomy of biological species. ITIS was originally formed in 1996 as an interagenc ...
''.
Animal Diversity Web: ''Bufo americanus''
{{Taxonbar, from=Q694496
Anaxyrus
Amphibians of the United States
Amphibians of Canada
Fauna of the Eastern United States
Fauna of the Great Lakes region (North America)
Amphibians described in 1836
Taxa named by John Edwards Holbrook