The Colorado River toad (Incilius alvarius), also known as the Sonoran Desert toad, is found in northern Mexico and the southwestern United States. It is notable for exuding toxins from glands within its skin that have psychoactive properties.
Description: The Colorado River toad can grow to about 7.5 inches long and is the largest toad in the United States apart from the non-native cane toad (Rhinella marina). It has a smooth, leathery skin and is olive green or mottled brown in color. Just behind the large golden eye with horizontal pupil is a bulging kidney-shaped parotoid gland. Below this is a large circular pale green area which is the tympanum or ear drum. By the corner of the mouth there is a white wart and there are white glands on the legs. All these glands produce toxic secretions. Its call is described as, "a weak, low-pitched toot, lasting less than a second."
Dogs that have attacked toads have suffered paralysis or even death. Raccoons have learned to pull a toad away from a pond by the back leg, turn it on its back and start feeding on its belly, a strategy that keeps the raccoon well away from the poison glands. Unlike other vertebrates, this amphibian obtains water mostly by osmotic absorption across its abdomen. Toads in the family bufonidae have a region of skin known as "the seat patch", which extends from mid abdomen to the hind legs and is specialized for rapid rehydration. Most of the rehydration is done through absorption of water from small pools or wet objects.
Habitat: It lives in both desert and semi-arid areas throughout its range. It is semiaquatic and is often found in streams, near springs, in canals and drainage ditches, and under water troughs. The Colorado River toad is known to breed in artificial water bodies (e.g., flood control impoundments, reservoirs) and as a result, the distributions and breeding habitats of these species may have been recently altered in south central Arizona. It often makes its home in rodent burrows and is nocturnal.
Range: The Colorado River toad is found in the lower Colorado River and the Gila River catchment areas, in New Mexico, Mexico and much of southern Arizona. It is considered possibly extirpated from California.
Diet: The Colorado River toad eats a wide variety of animals including spiders, insects, toads, snails, beetles, grasshoppers, mice, and small lizards.
Reproduction: The breeding season starts in July, when the rainy season begins, and can last up to August. Normally, 1-3 days after the rain is when toads begin to lay eggs in ponds, slow-moving streams, temporary pools or man-made structures that hold water. Eggs are 1.6 mm in diameter, 5-7 mm apart, and encased in a long single tube of jelly with a loose but distinct outline. The female toad can lay up to 8,000 eggs.
Status: Globally: species of least concern. Arizona classified as Vulnerable. California classified as extinct. New Mexico classifed as Imperiled.
Disclaimer: ITIS taxonomy is based on the latest scientific consensus available, and is provided as a general reference source for interested parties. However, it is not a legal authority for statutory or regulatory purposes. While every effort has been made to provide the most reliable and up-to-date information available, ultimate legal requirements with respect to species are contained in provisions of treaties to which the United States is a party, wildlife statutes, regulations, and any applicable notices that have been published in the Federal Register. For further information on U.S. legal requirements with respect to protected taxa, please contact the U.S. Fish and Wildlife Service.
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