Anaxyrus americanusAmerican Toad

Ge­o­graphic Range

Amer­i­can toads, Anaxyrus amer­i­canus, are only na­tive to the Nearc­tic re­gion. They are found through­out large por­tions of North Amer­ica, from north­ern Chi­huahua in Mex­ico, north­ward to James Bay in Canada and east­ward from the Im­pe­r­ial Val­ley of Cal­i­for­nia and the Co­lum­bia River Val­ley in Wash­ing­ton and Ore­gon to the At­lantic coast from Florida to south­ern Que­bec. They are gen­er­ally not pre­sent in the most south­ern states or, if they are, only in the north­ern part. These toads have an im­mense abil­ity to adapt to their sur­round­ings as long as there is a source of semi-per­ma­nent water for them to use in the breed­ing sea­son. This qual­ity has al­lowed them to suc­cess­fully col­o­nize sub­ur­ban and agri­cul­tural areas. (Dick­er­son, 1906; Oliver, 1955)

Habi­tat

Amer­i­can toads re­quire a semi-per­ma­nent fresh­wa­ter pond or pool 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 back­yards. They are com­mon in gar­dens and agri­cul­tural fields. Dur­ing day­light hours they seek cover be­neath porches, under board­walks, flat stones, boards, logs, wood piles, or other cover. When cold weather comes, these toads dig back­wards into their sum­mer homes or may choose an­other site in which to hi­ber­nate. (Le Clere, 2000; Lerner, June 13 1998; Mat­son, 2002; Rakestraw, 1998)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Phys­i­cal De­scrip­tion

Amer­i­can toads have short legs, stout bod­ies, and thick skins with no­tice­able warts. These warts can be col­ored red and yel­low. The warty skin con­tains many glands that pro­duce a poi­so­nous milky fluid, pro­vid­ing these toads with ex­cel­lent pro­tec­tion from many of their preda­tors. This poi­son is only harm­ful if it is swal­lowed or if it gets in the eyes, but it can make many an­i­mals very sick. (Dick­er­son, 1906; Le Clere, 2000; Mat­son, 2002; Oliver, 1955)

The skin color of Amer­i­can toads is nor­mally a shade of brown, but it can also be red with light patches, olive, or gray. The bel­lies are a white or yel­low color. Toad skin color changes de­pend­ing on tem­per­a­ture, hu­mid­ity, and stress. The color change ranges from yel­low to brown to black. Amer­i­can toads have four toes on each front leg and five toes con­nected to­gether by a web­bing on each hind leg. The pupils of Amer­i­can toads are oval and black with a cir­cle of gold around them. The sexes can be dis­tin­guished in two ways. Males have dark col­ored throats, of black or brown, while fe­males have white throats and are lighter over­all. Also, fe­male Amer­i­can toads are larger than male Amer­i­can toads. Amer­i­can toads are be­tween 50 and 100 mm in length but are usu­ally around 75 mm. Amer­i­can toads can be dis­tin­guished from other species of toads by the pres­ence of sev­eral dark spots on their backs which con­tain only one or two warts each. These black spots are some­times cir­cled with white or yel­low. Some types of Amer­i­can toads have a promi­nent ridge on the top of their heads. (Dick­er­son, 1906; Le Clere, 2000; Mat­son, 2002; Oliver, 1955)

The eggs of Amer­i­can toads are black on top and white on the bot­tom (coun­ter­shaded), and em­bed­ded in long strings of clear sticky gel. The lar­vae that hatch from eggs are called "tad­poles." They are dark (al­most black) with smooth skin, round bod­ies, and a some­what rounded tail. Like adult toads, lar­vae have de­fen­sive chem­i­cals in their skin. They grow to over a cen­time­ter in length be­fore trans­form­ing. Newly-meta­mor­phosed toadlets are usu­ally 0.8 and 1.3 cm long when they first emerge. Their col­oration is sim­i­lar to that of adult toads. (Dick­er­son, 1906; Le Clere, 2000; Mat­son, 2002; Oliver, 1955)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • Range length
    50 to 102 mm
    1.97 to 4.02 in
  • Average length
    75 mm
    2.95 in

De­vel­op­ment

Fe­male Amer­i­can toads lay their eggs in fresh­wa­ter. Hatch­ing oc­curs 3 to 12 days after lay­ing, de­pend­ing on the tem­per­a­ture of the water. The tad­poles group to­gether and feed and grow for 40 to 70 days.

When the tad­poles hatch they have gills lo­cated on the sides of their heads just pos­te­rior to their mouths. Dur­ing the first 20 days the tad­poles start to form their hind legs. The legs grow slowly, but con­tin­u­ously. After 30 to 40 days the front legs, which were pre­vi­ously cov­ered by a layer of skin, ap­pear. At the same time that the front legs emerge, the tad­poles' gills dis­ap­pear, and the tad­poles start to breathe "at­mos­pheric" air. Be­tween the last two or three days of de­vel­op­ment, they com­plete their meta­mor­pho­sis, re­sorb­ing their tails and strength­en­ing their legs. They also stop eat­ing plants in favor of an­i­mal mat­ter.

Newly-meta­mor­phosed toads stay near their pond for a few days (or longer if the cli­mate is dry), and then dis­perse and begin to live pri­mar­ily on land. Amer­i­can toads con­tinue to grow until they reach their full adult size of ap­prox­i­mately 75 mm.

Amer­i­can toads, while still grow­ing, shed their ex­ter­nal skin every cou­ple of weeks or so. Older frogs lose their skin around four times yearly. The skin peels off in one piece, and is col­lected under its tongue, where it is then gulped down. (Dick­er­son, 1906; Mat­son, 2002; Oliver, 1955)

Re­pro­duc­tion

Breed­ing oc­curs in the months of March or April, but may ex­tend into July. It usu­ally trig­gered by warm­ing tem­per­a­tures and longer days. The males al­ways ar­rive on the mat­ing grounds well ahead of fe­males. They con­gre­gate in shal­low wet­lands, ponds, lakes and slow-mov­ing streams. After find­ing a suit­able area, the male toads es­tab­lish ter­ri­to­ries and begin call­ing the fe­males. Fe­males may choose their mates by as­sess­ing the males' breed­ing calls as well as the qual­ity of the de­fended breed­ing ter­ri­tory.

Male toads get dark horny pads on their first and sec­ond two toes on their forelegs. This helps them close their front limbs around a fe­male's ab­domen in a pos­ture called "am­plexus". Once a fe­male comes close, any nearby male will at­tempt to mate with her. The male holds on to the fe­male, and she moves to a suit­able lo­ca­tion in the water to lay eggs. When she re­leases her eggs, he re­leases sperm to fer­til­ize them (like most frogs and toads, fer­til­iza­tion is ex­ter­nal).

After mat­ing takes place, the fe­males lay their eggs in the water, in long spi­ral tubes of jelly. They lay 4000 to 8000 eggs in two rows. When each row of eggs is stretched it gen­er­ally mea­sures be­tween be­tween six and twenty me­ters long (20 to 66 ft.). Each in­di­vid­ual egg is 1.5 mm in di­am­e­ter. The eggs ma­ture fastest at higher tem­per­a­tures. They gen­er­ally hatch in 3 to 12 days. After de­vel­op­ing for 40 to 70 days, the tad­poles trans­form into adults. This usu­ally takes place from June to Au­gust, de­pend­ing on lo­ca­tion. They reach sex­ual ma­tu­rity at around 2 to 3 years of age.

  • Breeding interval
    American toads breed from once yearly.
  • Breeding season
    American toads breed from March to July each year, depending on location.
  • Range number of offspring
    4000 to 8000
  • Range time to hatching
    2 to 14 days
  • Range age at sexual or reproductive maturity (female)
    2 to 3 years
  • Range age at sexual or reproductive maturity (male)
    2 to 3 years

Fe­male toads pro­vide nu­tri­ents for their eggs in­side their bod­ies. Once the eggs are laid and fer­til­ized, the par­ents ig­nore them.

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female

Lifes­pan/Longevity

In the wild most Amer­i­can toads prob­a­bly don't sur­vive more than a year or two. The ma­jor­ity die be­fore trans­form­ing from tad­poles into toadlets. How­ever, they are ca­pa­ble of liv­ing much longer. Some toads have lived longer than 10 years in the wild. There is a doc­u­mented ac­count of a cap­tive toad that lived to the ripe old age of 36 and was killed by mis­take. (Dick­er­son, 1906; Hard­ing, 1997; Oliver, 1955)

  • Range lifespan
    Status: wild
    0 to 10 years
  • Average lifespan
    Status: wild
    < 1 years
  • Range lifespan
    Status: captivity
    0 to 36 years

Be­hav­ior

Amer­i­can toads are mainly noc­tur­nal. They are most ac­tive when the weather is warm and humid. They are soli­tary, con­gre­gat­ing only at breed­ing ponds in the early sum­mer and late spring. Dur­ing the day Amer­i­can toads hide under rocks or logs or dig into dead leaves and soil. In re­gions with a cold win­ter, Amer­i­can toads dig deeper to hi­ber­nate. When dig­ging they back in, push­ing out dirt with their back legs.

(Hard­ing 1997, Mullin, 1998; Dick­er­son, 1906) (Dick­er­son, 1906; Hard­ing, 1997)

Com­mu­ni­ca­tion and Per­cep­tion

Amer­i­can toads have one of the most no­table calls of all toads. They give off long trill sounds that each last be­tween 4 and 20 sec­onds. Amer­i­can toads use this call as a way to at­tract fe­males for breed­ing. Their calls be­come fran­tic, loud, and con­stant dur­ing mat­ing sea­son. Many young males con­tinue to call late into the sum­mer. When they call, their throats puff out like large, in­flat­able bal­loons.

Amer­i­can toads also use body pos­tures, touch, and chem­i­cal cues for com­mu­ni­cat­ing.

Food Habits

Adult Amer­i­can toads are car­ni­vores, but toad tad­poles are con­sid­ered her­bi­vores, be­cause they graze on aquatic veg­e­ta­tion (algae).

Adult Amer­i­can toads are gen­er­al­ists. They eat a wide va­ri­ety of in­sects and other in­ver­te­brates, in­clud­ing snails, bee­tles, slugs, and earth­worms. Un­like most toads, who wait for prey to come along and pounce on it, Amer­i­can toads can shoot out their sticky tongues to catch prey. They also may use their front legs in order to eat larger food. They grasp their food and push it into their mouths. One Amer­i­can toad can eat up to 1,000 in­sects every day.

Toads do not drink water but soak it in, ab­sorb­ing mois­ture through their skin. (Hard­ing, 1997; Le Clere, 2000; Lerner, June 13 1998)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • terrestrial worms
  • Plant Foods
  • algae

Pre­da­tion

The main preda­tors of Amer­i­can toads are snakes. One species, east­ern hog­nose snakes, spe­cial­izes on eat­ing toads. Some snakes, such as garter snakes, are im­mune to the poi­so­nous glands of Amer­i­can toads. When these toads are faced with a preda­tor that is im­mune to their poi­son they will some­times uri­nate on them­selves to be­come a less at­trac­tive meal. They also in­flate their bod­ies with air to make them­selves more dif­fi­cult for a snake to swal­low.

Fe­male toads pre­fer to lay their eggs in ponds with­out fish. The eggs they lay are coun­ter­shaded: lighter on the bot­tom and darker on the top to blend in with the back­ground when viewed from above or below.

Tad­poles avoid preda­tors by swim­ming in very shal­low water, and by swim­ming close to­gether in schools dur­ing the day. They also have toxic chem­i­cals in their skin that dis­cour­age some po­ten­tial preda­tors. Meta­mor­phosed toads are cryp­ti­cally col­ored, and are ac­tively mainly at night, mak­ing it harder for preda­tors to find them. (Dick­er­son, 1906; Hard­ing, 1997; Le Clere, 2000)

  • Anti-predator Adaptations
  • cryptic

Ecosys­tem Roles

Amer­i­can toads are re­spon­si­ble for con­trol­ling the pop­u­la­tions of many kinds of in­sects. The num­ber of in­sects they eat makes them a cru­cial part of con­trol­ling these pop­u­la­tions. (Dick­er­son, 1906)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Amer­i­can toads eat many species of pest in­sects and other in­ver­te­brates. They are widely con­sid­ered friends to gar­den­ers and farm­ers. The tox­ins pro­duced by their skin may even­tu­ally prove use­ful in med­ical re­search. (Dick­er­son, 1906)

  • Positive Impacts
  • research and education
  • controls pest population

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no neg­a­tive im­pacts of Amer­i­can toads on hu­mans.

Con­ser­va­tion Sta­tus

Amer­i­can toads have no spe­cial con­ser­va­tion sta­tus, as they are still com­mon in most of their range. Some pop­u­la­tions have de­clined in re­cent years, pos­si­bly due to pol­lu­tion.

Other Com­ments

Amer­i­can toads are the most wide­spread toad species in North Amer­ica.

There are two sub­species of Amer­i­can toads, east­ern and dwarf. Dwarf Amer­i­can toads live mainly in the west, east­ern Amer­i­can toads live in the east­ern por­tions of the range.

Con­trary to folk-be­lief, you will not get warts if you touch a toad. How­ever, the de­fen­sive chem­i­cals in toad skin are toxic to hu­mans, so its im­por­tant to wash one's hands care­fully after han­dling one.

Con­trib­u­tors

Al­li­son Poor (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Stacey Gross­man (au­thor), Fresno City Col­lege, Carl Jo­hans­son (ed­i­tor), Fresno City Col­lege.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

choruses

to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

freshwater

mainly lives in water that is not salty.

herbivore

An animal that eats mainly plants or parts of plants.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

poisonous

an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

polygynous

having more than one female as a mate at one time

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

suburban

living in residential areas on the outskirts of large cities or towns.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

Ref­er­ences

1999. "Ohio His­tory Cen­ter" (On-line). Ac­cessed Sept. 20,2001 at http://​www.​ohiohistorycentral.​org/​ohc/​nature/​animals/​reptile/​americantoad.​shtml.

Dick­er­son, M. 1906. The Frog. NY: Dou­ble­day, Page and Com­pany.

Hard­ing, J. 1997. Am­phib­ians and Rep­tiles of the Great Lakes Re­gion. Ann Arbor, Michi­gan, USA: The Uni­ver­sity of Michi­gan Press.

King, R., M. Old­ham, W. Weller, D. Wynn. 1997. His­toric and cur­rent am­phib­ian and rep­tile dis­tri­b­u­tions in the is­land re­gion of west­ern Lake Erie. Amer­i­can Mid­land Nat­u­ral­ist, 138 (1): 153-173.

Le Clere, J. 2000. "Amer­i­can Toad" (On-line). Ac­cessed Sept. 20,2001 at http://​herpnet.​net/​Iowa-Herpetology/​amphibians/​frogs_​toads/​american_​toad.​html.

Lerner, J. June 13 1998. Grow­ing a Gar­den of Wildly De­lights. The Wash­ing­ton Post: G 16.

Mat­son, T. 2002. "An In­tro­duc­tion to the Nat­ural His­tory of the Frogs and Toads of Ohio" (On-line). Ac­cessed Sept. 20,2001 at http://​www.​cmnh.​org/​collections/​vertzoo/​frogs/​americanus.​html.

Mil­ius, S. 1998. Fatal skin fun­gus found in U.S. frogs. Sci­ence News, 154(1): 7.

Oliver, J. 1955. The Na­tional His­tory of North Amer­i­can Am­phib­ians and Rep­tiles. Prince­ton: D. Van Nos­trand Com­pany. Inc..

Rakestraw, J. 1998. Turn­ing Over Rocks. Coun­try Jour­nal, 25 (3): 52-56.

With­gott, J. 2001. Feel­ing The Burn. Nat­ural His­tory, 110(6): 38-45.