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toad, name commonly used for squat, rough- skinned, tailless amphibians (order Anura), especially those of the family Bufonidae. The true toads (Bufo), with more than 150 species, are found worldwide except in Australasia and Madagascar. Besides Bufo, the family includes 12 genera, one of which (Necrophrynoides) contains the only anuran that bears live young.
Variegated toads (Atelopus) are found in South and Central America. Placed by some authorities in the family Atelopodidae, these bufonids are commonly square headed and have enlarged hindfeet. Some are brightly coloured in black with yellow, red, or green. When molested, the small, poisonous A. stelzneri of Uruguay bends its head and limbs over its body to display its bright-orange hands and feet. This position may be a method of warning the intruder of the toxicity of the toad.
True toads, of which the American toad (Bufo americanus) and the European toad (B. bufo) are representative, are stout bodied with short legs that limit them to the characteristic walking or hopping gait. Size ranges from about 2 to 25 centimetres (1 to 10 inches). The thick, dry, often warty skin on the back is generally mottled brown. Poison- secreting glands are located on the back and in the warts but are most concentrated in two prominent raised areas behind the eyes, the parotoid glands.
The poison, which is secreted or ejected when the toad is molested, irritates the eyes and mucous membranes of many, though not all, predators. The poisons of the Colorado River toad (B. alvarius) and the giant toad (B. ,narinus) affect animals as large as dogs, in some instances causing temporary paralysis or even death. The Chinese have long used dried toad poison to treat various ailments, but most of the important substances can be synthesized or obtained from better sources. Contrary to popular belief, toads do not cause warts.
True toads are mainly terrestrial and nocturnal. They frequently remain in fairly small areas, feeding on whatever insects or small animals they can catch. Some species have been introduced to control insect pests; a favourite is the giant toad, native to Central and South America and now established in the United States, Philippines, and elsewhere. Most true toads remain in their burrows in winter and during drought. They breed in water and inay migrate 1.5 kilometres (one mile) or more to a suitable breeding pond. The eggs (600 to over 30,000, depending on species) are laid in two long jelly tubes. The tadpoles hatch in a few days and transform into adults in one to three months.
