American Toad
Bufo americanus
Summary: This habitat generalist occurs at almost all sites inventoried in the region to date. It is known from every county, with the largest populations typically in relatively open uplands and along river floodplains.
Description: American toads are of medium-size, 2.0 to 4.4 inches (5.1-10.1cm), and of stocky build. Large paratoid glands are located at the back of the head. The skin of the upper surfaces is rough and covered with warts. Color is variable, usually some shade of brown, tan, or reddish brown. There are a few small dark spots on the back. The underside is whitish to light tan, with dark mottling heaviest in the chest area.
In most of the region this is the only toad. The Fowler's toad occurs in the area but has a limited distribution. The American toad can be distinguished by
- the presence of dark mottling on the underside;
- usually only one or two warts within each dorsal dark spot; and
- the cranial crests well separated from the paratoid glands.
Habitat: American toads are habitat generalists. Relatively open habitats are preferred; sites with grassland or savanna structure tend to support large populations, as do open floodplain forests. More heavily wooded habitats are also used, but usually at much lower densities. In northern flatwoods I typically captured only a few individuals each year, while observations were frequent in nearby floodplains and savannas. Toads seem to make little distinction between high-quality and degraded sites. I have even found a few toads inside active cropland, and they are the only local amphibian with that dubious distinction.
Breeding takes place in shallow and usually ephemeral wetlands, including marshes, vernal ponds, oxbow ponds on floodplains, and even in water-filled tire ruts.
Voice: A sustained musical trill, often lasting for up to 30 seconds. It is one of the more pleasant mid-spring sounds.
Phenology: Toads are occasionally unearthed from shallow burrows or from under logs in early spring, but surface activity usually does not occur until breeding begins in late April or very early May. If warm, wet conditions arrive suddenly, migrations to ponds can be explosive. Once in Ogle County, just west of our region, I saw hundreds of toads crossing a major highway in an evening thunderstorm.
Several thousand eggs are deposited in strings, either loose on the pond bottom or tangled in vegetation. They hatch quickly in the warm shallow water, usually in about a week (Smith, 1961). The small dark tadpoles also develop quickly, and leave the ponds in mid to late June. The ability to utilize relatively ephemeral ponds is one very important reason for the abundance of this species.
Field Notes
April 25, 1986. Lake County, IL. Brief but intense rain before 10:00pm. On the way out saw a large female Bufo americanus on the road.
May 9, 1988. Will County, near the Des Plaines River. Heavy thunderstorms and tornado warnings last night after two days in the low 80s. Today 60s and mostly cloudy, some drizzle. Bufo americanus calling occasionally from various parts of the marsh, found two live toads, and one dead.
May 11, 1988. Will County, near Lockport. Numerous Bufo tadpoles in a sedge meadow pool. Later found Bufo eggs in a small quarry pit.
June 25, 1996. Lake County, IL, Spring Bluff. Numerous Bufo and large Rana tadpoles.
June 27, 1996. Lake County, IL, Spring Bluff. 4:00 to 5:00pm, warm, mid-80s and sunny. Hundreds of Bufo metamorphs with stub tails clustered around part of the wetland margin along 7th Street.
Literature Cited
Smith, P. W. 1961. The amphibians and reptiles of Illinois. Illinois Natural History Survey Bulletin 28(1):1-298.
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| Updated: October 9, 2007
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