Anaxyrus canorus, the Yosemite toad, is endemic to the Sierra Nevada of California, from Alpine County south to Fresno County. It is a stocky, medium-sized toad, 48–84 mm snout-vent length, with females averaging larger than males1, and its species name, canorus, means “tuneful” — a nod to the male’s distinctive call. The U.S. Fish and Wildlife Service notes that Yosemite toads have low tolerance for extreme cold and heat2, so even a slight climate shift could harm them.
Identification
The Yosemite toad is considered the most sexually dichromatic frog species in North America: males are plain yellow-green to olive-drab, sometimes flecked with black, while females carry black blotches edged in white or cream on a tan, copper or ruddy background. Both sexes show large, irregularly shaped parotoid glands set less than one gland-width apart, narrowly spaced eyes, and large, smooth warts separated by smooth skin, with no prominent mid-dorsal stripe. The iris is dark brown with gold flecks. Those parotoid glands secrete a white toxin that deters predators3, the same bufotoxin defence4 documented in other true toads such as the American toad. Tadpoles are jet black throughout, 10–37 mm long1, with a short blunt snout and a rounded tail tip.
Habitat and range
The species lives in montane to subalpine wet meadows and snowmelt ponds, between 1,950 and 3,445 m elevation. It favours flatter, southwest-facing meadows that collect more precipitation and warm faster, with breeding water usually less than 5 cm deep1. Outside the breeding season, adults move to upland ground with seeps, springs, willow thickets, tall forbs, granite boulders and rodent burrows, which play an essential role as shelter, and the species shows high fidelity to the same breeding pools and upland refuges year after year. Living this high up means crossing late-season snow is routine, and the toad does it without sinking in: it has been nicknamed “the toad that stays on its toes” for crossing snowdrifts without its belly touching the surface.
Behaviour and breeding
Males are explosive breeders that arrive at meadow pools while snowbanks cover roughly half the ground, with the U.S. Fish and Wildlife Service placing the breeding window from May to July, which Animal Diversity Web extends to mid-August. A calling male produces a high, flute-like trill of 26–51 evenly spaced notes lasting about 2.6 seconds. A female lays 1,500 to 2,000 eggs per clutch in one or two strands tangled in vegetation, each egg about 2.1 mm across, swelling to 4.1 mm with its jelly envelope. The tadpoles graze on algae and detritus and will scavenge other tadpoles. Toads reach sexual maturity slowly, males at 3–5 years and females at 4–6 years2, and can live a long time once mature: at least 12 years for males and 15 for females in the wild. Largely diurnal thanks to the cold mountain air, adults eat ants, beetles, spiders, bees and wasps3, a diet described in more detail elsewhere as hymenopterans such as bees and wasps, beetles, craneflies, mosquitoes, caterpillars, dragonfly naiads, centipedes, millipedes and spiders, with hymenopterans alone making up roughly 80% of the adult diet1. Adults retreat to rodent burrows or willow thickets to hibernate once the first freezing nights arrive, typically in September or October.
Conservation
The IUCN Red List classed the Yosemite toad as Vulnerable in its 2022 assessment5. It has also been listed as Threatened under the U.S. Endangered Species Act since 2014. Its narrow elevational band and dependence on specific snowmelt meadows leave it vulnerable to decline: the U.S. Fish and Wildlife Service lists habitat loss, disease, climate change and other mortality2 among the causes, with drought, worsened by climate change, and chytridiomycosis disease1 considered the two most significant threats.
Similar species
The closest look-alike across its Sierra Nevada range is the western toad (Anaxyrus boreas). The Yosemite toad is distinguished by its larger, more narrowly spaced parotoid glands1, narrower eye spacing, smoother warts and the absence of a prominent mid-dorsal stripe, a combination the western toad does not show; calling males also carry vocal sacs, which western toad males lack. Farther from its range, other members of the former Bufo group in the western United States, such as the black toad and the Amargosa toad, lack the vocal sac needed to produce the Yosemite toad’s musical trill at all.
