HerpIndiana

American Toad (Anaxyrus (Bufo) americanus)

Adult americanus from Jefferson County

Description

Morphology: A large, stocky toad with a wide variety of red, brown, and gray color variations. There may be some dark blotches dorsally. These blotches encompass only one or two warts. Ventrally, there is usually some dark mottling or speckling. The legs have some indistinct banding. The Eastern American Toad (Bufo americanus americanus) is very variable in coloration. The Dwarf American Toad (Anaxyrus americanus charlesmithi) is reddish in coloration with reduced ventral pigmentation (Minton 2001, 108-109).

Size: The Eastern American Toad (Anaxyrus americanus americanus) may range from 2 to 4in SV length. The Dwarf American Toad (Anaxyrus americanus charlesmithi) only grows to around 2.5in (Conant and Collins 1998, 514-515).

Larvae: A small and dark tadpole rarely exceeding 1in in length. There is no patterning on the tail (Conant and Collins 1998, 574).

Eggs: Females lay their eggs in strands of up to 10,000 eggs (Minton 2001, 111).

Similar Species: The Fowler's Toad (Bufo fowleri) can be difficult to distinguish from this species and the two occasionally hybridize. American Toads rarely have dorsal blotches that enclose more than one or two large warts, whereas Fowler's Toads often have blotches that enclose multiple smaller warts. While American Toads may have heavy dark mottling ventrally, Fowler's Toads usually have either one large spot or no dark coloration at all. American Toads have enlarged tibial warts that Fowler's Toads lack. The cranial crest of the American Toad is pronounced and either disconnected to the paratoid gland or only connected via a spur while the Fowler's Toad has a much less prominent cranial crest that sits directly on top of the paratoid gland. While coloration is by no means a certain way to identifiy this species, American Toads are more often reddish or brown in coloration while Fowler's Toads tend to be grayish or olive-gray in coloration.

Distribution

The American Toad occurs throughout much of eastern Canada and the eastern United States, but is absent from most of the southeastern states (Conant and Collins 1998, 514).

This species occurs throughout Indiana except for much of the southwestern lowlands. While Eastern American Toads (Bufo americanus americanus) are found across most of the state, the Dwarf American Toad (Bufo americanus charlesmithi) is restricted to southern Indiana and its distribution is spotty (Minton 2001, 110). I have found many populations where some individuals show more characteristics of charlesmithi and others are typical americanus.

Activity

American Toads are most active from March to October with winter activity being observed only rarely.

Breeding Season: This species begins calling in late March and will continue breeding through most of May. In northern Indiana some breeding has been observed through June. After being deposited, the eggs may take anywhere from a couple days to a couple weeks to hatch. The larvae usually transform in June or July (Minton 2001, 111).

Taxonomy

The Eastern American Toad (Bufo americanus americanus) occurs throughout most of Indiana. The Dwarf American Toad (Bufo americanus charlesmithi) has a spotty occurence throughout southern Indiana where it often integrades with the Eastern American Toad. The American Toad belongs to the genus Bufo and is in the family Bufonidae which is represented in Indiana by 2 different species. In some populations this species hybridizes with the Fowler's Toad (Bufo fowleri).

Natural History

Habitat: This species inhabits a very wide variety of habitats. They are found in moist upland woods, marshes, suburban areas, and along riparian corridors. They are often spotted hopping around by day, but on rainy nights huge numbers of these toads can be seen crossing roads. Adults and juveniles can be regularly turned up under rocks along creeks. Sometimes they can be found in loose soil, burrowed down in shallow holes with only their heads looking out.

Feeding: A variety of insects and spiders, as well as earthworms make up the bulk of this frog's diet (Minton 2001, 112).

Breeding: In Indiana, this frog breeds in almost any source of still water. They will utilize woodland pools, marshes, shallow backwaters of lakes, areas where a stream pools, and even artificial goldfish ponds for breeding. Amplexus takes place in shallow, calm water. The male clasps the female and as the females expels strands of eggs, the male fertilizes them externally. Oftentimes multiple males will attempt to clasp one female, resulting in a ball of toads clasped together in somewhat of a breeding frenzy. This occasionally can result in individuals drowning.

Call: American Toads have a high pitched trill that generally lasts a few seconds, but may last up to 30 seconds (Behler and King 1998, 387). When picked up, males will usually give a high pitched peeping call or broken trill that is typically given when a male grabs another male by mistake during breeding.

Conservation: This species is widespread and adapts well to most habitats including heavily disturbed areas. There are no known immediate threats to the well being of this species in Indiana.

Potentially Harmful? It is a common myth that Toads cause warts when handled, but this is in no way true. Toads do however, have mildly toxic secretions that are used as a defensive mechanism against predators (Minton 2001, 112). These are not dangerous to humans unless ingested, but it is wise to wash your hands thoroughly after handling this species.