Friday, May 9, 2003
Biodiversity Corner: American Toad
Name: American Toad or Bufo americanus, the common garden "hoptoad."
When and where seen: This is your common warty garden toad. On Sunday, April 27
Distinguishing characteristics: Warts! The dry skin on
the back of the American toad is mottled brown, reddish brown, or gray
with dark blotches. There are one or two warts in the dark blotches.
The belly is white with black speckles. The eyes have a black, horizontal,
oval pupil rimmed by a metallic golden-colored iris. "Oh mark the
beauty of his eye, what wonders in that circle lie! So clear, so bright,
our fathers said — 'He wears a jewel in his head.' " Adult
males are about 2.5 to 3 inches long; females are an inch or so longer.
Department of Defense: Behind each eye there is a large parotid gland which produces a toxin that deters predation by most mammals. Dogs try only once to eat a toad. Skunks roll the toad about, getting it to release the toxin and rendering it edible. Raptors and snakes seem to be immune to the toxin. Toads also protect themselves by using camouflage and burrowing to hide from predators.
Vocalization: The American toad makes four different sounds. Some are just chirps or clicks but the advertisement call is the "song" you are likely to hear in April and May, day or night. You might have expected a song in the hip-hop style, or something patriotic like "Proud to be an American," but you get a sweet trilling musical call that can last for 30 seconds or more. Both Dickerson and Tyning (see References below) claim that the sound can be imitated by whistling and humming at the same time! The Dickerson description is reminiscent of Tuvan throat singing — "it seems to have a dual character, as though a low note were droned at the same time that a high note was whistled." As with Tuvans, only the males sing.
Food and Drink: Toads eat earthworms and a large variety of insects — flies, mosquitoes, ants, grubs, beetles — just about any small invertebrate that is out in the late afternoon and at night. A study done in 1906 found that 88% of a toad's food was made up of insect pests, of which 20% was cutworms. In an attempt to determine the economic value of a single toad, the study estimated that if the injury done by a single cutworm was as little as one cent per year, then a toad was worth $19.88 per year. Toads don't "drink" but absorb water through their skins.
Life cycle: Eggs are laid in a pair of long gelatinous strands. In about a week, they hatch into tadpoles which take another 4 weeks to metamorphose into tiny toads about half an inch long. The little toads leave the pond and move into woodlands and suburban yards. They return to ponds to breed when they are three or four years old. Toads live to ten years in the wild and up to 35 years in captivity.
References: Leo P. Kenney and Matthew R. Burne, A Field Guide to the Animals of Vernal Pools; Thomas F. Tyning, Stokes Nature Guides, A Guide to Amphibians and Reptiles; Mary C. Dickerson, The Frog Book.
© 2003 The Carlisle Mosquito