Bufo canorus
Yosemite toad

Yosemite toads are found in a small area of the Sierra Nevada Mountains in California. They have never been found outside of California. Bufo canorus range from the Blue Lakes region of Ebbets Pass to Kaiser Pass located near Evolution Lake in the Darwin Canyon area. They are found at high elevations in only two Californian counties, Alpine and Fresno counties. (Hammerson, October 2002; Leonard, 2002)

Yosemite toads are found in wet mountain meadows, often near pine forests. Even though they spend most of their time on land, they are never far from a permanent body of water. In their juvenile stage, Yosemite toad tadpoles swim in shallow pools of melted ice water, and in slow moving mountain streams. Bufo canorus live at high elevations, anywhere from 1950 meters to 3450 meters up on a mountain side. These grassland amphibians burrow under the soil, crawl beneath rocks and fallen logs and seek shelter in abandoned rodent holes during the night. (Davidson and Kagarise Sherman, July 1994; Hammerson, October 2002)

Bufo canorus are moderate size amphibians ranging from 4.5 cm to 7.5 cm. They show the highest degree of sexual dichromatism, different coloration between sexes, found among Californian toads. As in most sexually dimorphic animals, males exhibit brighter colors than females. Yosemite toad males are olive green to yellow green with small dark flecks, while females are gray or brown with large dark spots. (Davidson and Kagarise Sherman, July 1994; Kagarise Sherman, 1980; Romanisic and Chaver, 2002; Shaffer et al., 2000)

The young tadpoles look nothing like the adult toads, but it only takes them 7 to 9 weeks to metamorphose into adults. Yosemite toads are closely related to three other toads, the black, western and Amargosa toads. Together they make up the "boreas group." The Yosemite toads' high degree of sexual dichromatism distinguishes them from their relatives. Other features that distinguish the B. canorus from closely related species are their smaller size, wider paratoid glands and lack of a vertebral stripe. (Davidson and Kagarise Sherman, July 1994)

Yosemite toads lay their eggs in shallow pools of water from May to mid August. Eggs hatch in 10 to 12 days and tadpoles metamorphose into adults seven to nine weeks after hatching. The first few years of Bufo canorus lives are not reproductive. Females reach reproductive age at four to six years and males at three to five years. (Davidson and Kagarise Sherman, July 1994)

The biggest cause of mortality among tadpoles is desiccation. When the snowfall is low the pools of water that form in the spring dry up too quickly for the toads to metamorphose in time. Recent drought in California may be one reason this toads' population has greatly declined. (Davidson and Kagarise Sherman, July 1994; Shaffer et al., 2000)

B. canorus is a long living species. Females live at least 15 years while males live shorter lives of at least 12 years. (Davidson and Kagarise Sherman, July 1994; Kagarise Sherman, 1980)

Yosemite toads are only active during the day. During the night they burrow in soil, under logs, and in rodent tunnels. They are solitary creatures except during the breeding season, when males are found congregated around shallow pools of water emitting their melodious trills. B. canorus start hibernation in late September or early October, and they come out of their deep sleep sometimes in April, May or July depending on temperature. Even though the Yosemite toads keep to themselves they are not territorial. (Davidson and Kagarise Sherman, July 1994; Kagarise Sherman, 1980)

During breeding season B. canorus males assemble in the day and call to the females in choruses. Their melodious calls are often mistaken for bird calls. (Davidson and Kagarise Sherman, July 1994; Leonard, 2002)

The feeding patterns of the adult and larvae Yosemite toads differ. Bufo canorus larvae eat plankton and detritus, while the adults are primarily insectivorous. In the summer, hymenopterans are a major part of the toads' diet. Some specific foods of B. canorus are ants, centipedes, spiders, ladybird beetles, mosquitoes, weevils, tenebrionid beetles, and millipedes. (Davidson and Kagarise Sherman, July 1994; Hammerson, October 2002; Romanisic and Chaver, 2002)

It may be that the coloration of B. canorus makes it hard to spot for predators. These toads' main defense mechanisms against predation, however, are their poison glands. Like many other toads, this species has enlarged paratoid glands at the side of its neck. The paratoid glands secrete a white poison that protects the Yosemite toads from prospective predators by causing nausea, inflammation of the mouth, or irregular heart beat. This poses a danger to the toads' predators and can be irritating to humans if it gets into the mouth or eyes. In extreme cases the poison can cause death to its ingestor. The taste of the mucous-like poison is also very unpleasant. (Davidson and Kagarise Sherman, July 1994; Hammerson, October 2002; Leonard, 2002; Romanisic and Chaver, 2002)

The Yosemite toads and tadpoles provide a minor food source for birds and snakes in the Sierra Nevada Mountain ecosystem. Their number and success may be an indicator of the amount of pollution in that ecosystem, but this has not yet been determined. The toads' soil burrowing habits may also contribute minimally to the aeration of the soil. (Davidson and Kagarise Sherman, July 1994; Hammerson, October 2002)

The poison in the paratoid glands of the Yosemite toads irritates the skin and causes inflammation, and may be dangerous to humans if it gets into the eyes and mouth. (Leonard, 2002)

Yosemite toads may be beneficial to people by controlling populations of insects. The poison in the paratoid glands may also be beneficial once researched.

In addition to its listing as an endangered animal on the IUCN Red List, Bufo canorus is a Category 2 candidate for listing as an Endangered Species by the United States fish and Wildlife Service. Vehicular traffic kills, prolonged periods of drought, and disease all claim partial responsibility in the rapid decline of Bufo canorus. Attempts are being made at various zoological institutions throughout the U.S. to successfully breed and reintroduce this species back into its native range. (Romanisic and Chaver, 2002)