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Incilius alvarius

By Rachel Brunelle

Geographic Range

Incilius alvarius is found in the northern parts of Mexico, the southern parts of Arizona and New Mexico, and the southeast corner of California (Stebbins 1985, Robinson 2001).

Habitat

The main part of its range is from sea-level to 1600 m (5300 ft). It can be found in a variety of desert and semi-arid habitats: brushy desert with creosote bush and mesquite washes, semi-arid grasslands and woodlands. It is semi-aquatic and is usually associated with large, somewhat permanent

streams. It is occasionally found near small springs, temporary rain pools, human-made canals and irrigation ditches. They frequently live in rodent burrows (Robinson 2001, Mayhew 1968).

Physical Description

Dark olive green color and leathery skin. They are 110-187mm in length. A very large toad with cranial crests, elongate parotid glands, raised warts on hind legs (Robinson 2001).

Development

Reproduction

These toads appear when the summer showers start and breed in the temporary pools that form after the rains begin. Males croak incessantly, but have a relatively weak call, compared to other frogs and toads. They are an egg laying species and the larval period is believed to be 1 month. The tadpoles are a yellow/brown color (Mayhew 1968, Robinson 2001, Stebbins 1985).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)

Lifespan/Longevity

Behavior

Incilius alvarius is nocturnal and more aquatic than most toad species. It is a solitary species, until the mating season in the summer months when large groups of toads gather at temporary pools to mate. If the toad is molested or bothered, it can secrete a poison which irritates the mucous membranes of most predators. This poison can affect animals as large as dogs, and can cause temporary paralysis or death (Mayhew 1968, Robinson 2001).

Food Habits

Incilius alvarius is carniverous and is known to eat snails, beetles, spiders, grasshoppers, lizards, mice, and other smaller toad species. A long sticky tongue aids in catching prey (Mayhew 1968).

Economic Importance for Humans: Positive

Control crop pests such as snails (Mayhew 1968).

Conservation Status

Contributors

Rachel Brunelle (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

References

Mayhew, W. 1968. The biology of desert amphibians and reptiles. New York: Academic Press.

Robinson, A. 2001. "Amphiba web" (On-line). Accessed 3/22/01 at http://elib.cs.berkeley.edu/cgi-bin/amphib_query?table=amphib&special=one_record&where-genus=Bufo&where-species=alvarius.

Stebbins, R. 1985. A field guide to western reptiles and amphibians. Boston: Houghton Mifflin.

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