Adults are usually 110-187mm long from snout to vent. Their olive skin is smooth, leathery, and scattered with small rounded tubercles. Behind the angle of the jaws there is at least one conspicuous white tubercle. The length of each paratoid gland is twice the paratoid width, and equal to the distance from the nostril to the tympanum. On the dorsal surfaces of the limbs there are several enlarged glands that resemble the paratoids. Above each eye curves a distinct cranial crest.
 
The glands of the toads produce a toxin that can cause intoxication in humans, and therefore is a controlled substance.

See another account at californiaherps.com.

This species occurs from extreme southeastern California, southern Arizona and extreme southern New Mexico in the USA, south into Mexico. It has nearly been extirpated in California. It occurs from sea level to 1,610m asl (Stebbins 1985).

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).

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: This species occurs from extreme southeastern California, southern Arizona and extreme southern New Mexico in the United States, south in to Mexico. It has nearly been extirpated in California. It occurs from sea level to 1,610m asl (Stebbins 1985).

Found from southern Arizona(USA), through most of Sonora to northern Sinaloa (Mexico). Its range extends into the southeastern parts of California, USA and the northeastern corner of Baja California, Mexico. These toads are primarily found in the desert, but also occur in grassland and lower oak-woodland. They frequently take refuge in rodent burrows. Though they often breed in temporary pools, they appear to be dependant on the presence of a permanent water source.

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).

Length: 18 cm

Lectotype; Syntype for Incilius alvarius
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1855
Locality: Fort Yuma, Imperial, California, United States, North America

Habitat and Ecology

Systems

• Terrestrial
• Freshwater

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).

Comments: This species ranges from arid mesquite/creosotebush lowlands and arid grasslands to oak/sycamore/walnut groves in mountain canyons. It is often near permanent water but is also found near temporary water or far from water. It may take refuge in rodent burrows. It breeds and lays eggs in ponds, slow-moving streams, etc.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Migrates short distances between breeding and nonbreeding habitats.

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).

Comments: Feeds on insects and spiders as well as lizards and other toads (Behler and King 1979).

Comments: Inactive in cold temperatures and hot, dry weather. Most active during the breeding season, May-July. Activity stimulated by rainfall, but not dependent on rainfall for breeding (Stebbins 1985).

Average lifespan

Status: captivity: 9.2 years.

Maximum longevity: 15.4 years (captivity)

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).

Breeding occurs May-August, usually for a short period (one or two nights), 1-3 nights following a major rainfall event; relatively few of the males produce persistent advertisement calls (Sullivan and Malmos, 1994, Herpetologica 50:146-156). May lay up to about 8,000 eggs in long strands (Stebbins 1972)

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Intrinsic Vulnerability: Moderately vulnerable

Environmental Specificity: Moderate. Generalist or community with some key requirements scarce.

Population

Population Trend

Global Long Term Trend: Decline of 30-50%

Comments: Likely relatively stable in extent of occurrence, unknown degree of decline in population size, area of occurrence, and number/condition of occurrences.

These toads appear in Tuscon just prior to the summer showers, and congregate once the rains begin. They breed in temporary pools, croaking incessantly. Males have a reduced vocal sac and their call is weak. Their eggs are strikingly different from those of related species B. boreas and B. canorus. The larval period is believed to be no more than a month. Their diet includes beetles, grasshoppers, spiders, small lizards, Bufo cognatus and Scaphiopus couchi.

Major Threats

Comments: No major threats have been identified (other than localized ones) for this species.

Habitat destruction and possibly pesticide use have caused populations to become extinct. Collecting by certain groups is also a threat to populations in some areas. Little more is known, therefore conservation efforts are limited.

Conservation Actions

Control crop pests such as snails (Mayhew 1968).