What You Need to Know About Bufo Canorus, the Yosemite Toad
Bufo canorus, also known as the Yosemite toad, is a species of true toad in the family Bufonidae. It is endemic to the Sierra Nevada of California, where it lives in montane and subalpine meadows and wetlands. Bufo canorus is one of the most sexually dichromatic anurans in North America, with males and females having different colors and patterns. Bufo canorus is also the only member of its genus that has a vocal sac and produces an advertisement call to attract mates.
Bufo canorus was first described in 1916 by Charles Camp, an undergraduate student of Joseph Grinnell, during the Grinnell Survey of California. Camp named the species “canorus” meaning tuneful, because of its melodious call. Bufo canorus was later moved to the genus Anaxyrus, along with other North American toads, based on molecular evidence.
Bufo canorus is a medium-sized toad, with females averaging larger than males. Females have a tan, copper, or ruddy background color with black blotches that have white or cream borders. Males are more uniformly colored, ranging from yellow-green, to olive drab, to greenish brown, sometimes with scattered black flecks near warts. Juveniles resemble adult females, except with a thin mid-dorsal stripe that fades during development. Bufo canorus has large, smooth warts and large, narrowly spaced parotoid glands. Its eyes have a dark brown iris with gold iridophores.
Bufo canorus breeds in shallow pools and ponds in meadows and wetlands from late April to early July, depending on elevation and snowmelt. Males arrive at the breeding sites first and establish territories by calling. Females select mates based on male size and call characteristics. The pair forms amplexus and the female deposits a single string of eggs attached to vegetation or rocks. The eggs hatch in a few days and the tadpoles metamorphose in 6 to 8 weeks. Bufo canorus tadpoles are dark brown or black with gold flecks and have a rounded tail tip.
Bufo canorus is mainly active during the day, but may also be active at night during warm weather. It feeds on a variety of insects and other invertebrates, such as ants, beetles, flies, spiders, worms, and snails. Bufo canorus avoids predators such as garter snakes, birds of prey, coyotes, and bears by hiding under rocks, logs, or vegetation. It may also secrete toxins from its parotoid glands or inflate its body to deter predators.
Bufo canorus is listed as vulnerable by the IUCN Red List and threatened by the U.S. Fish and Wildlife Service. Its population has declined by more than 50% over the last 30 years due to habitat loss and degradation, disease, predation by introduced trout, climate change, drought, fire suppression, grazing, recreation, and pesticides. Conservation efforts for Bufo canorus include habitat restoration and protection, disease monitoring and management, trout removal or exclusion from breeding sites, captive breeding and reintroduction programs, public education and outreach.
Bufo canorus is a unique and charismatic species that plays an important role in the ecology of the Sierra Nevada. By learning more about Bufo canorus and its threats, we can help conserve this tuneful toad for future generations.