Decline, movement and habitat utilization of the Yosemite toad (Bufo canorus): An endangered anuran endemic to the Sierra Nevada of California

Since 1990 there has been an accumulation of evidence suggesting that global amphibian populations have declined. The majority of these declines can be explained by habitat destruction, but some have occurred in seemingly "pristine" habitats such as the high elevation Sierra Nevada mountains of California where the Yosemite toad (Bufo canorus), which is endemic to these "pristine" habitats in the Sierra, has declined. Unfortunately, the designation of "pristine" habitat is based on general management goals rather than on the habitat utilized by amphibians. This study used radio transmitters to track the movements of toads to determine what habitats are utilized and found that adult B. canorus are capable of traveling up to 657m (X¯ = 278m) from breeding pools to upland foraging habitats, thereby providing a mean total home range estimate for adult B. canorus of 8,457m2, which is considerably larger than previously suggested. Further, this study found that B. canorus conducts much of its movements at night and is therefore not strictly diurnal as previously reported. The habitat utilized by B. canorus was found to include meadows, which were used predominantly by subadult toads and matched the reported preferred habitat of lush meadows with willows and a mean vegetation height of 25cm; upland foraging habitat, which is predominantly occupied by adults and is characterized by rocky substrate and lush vegetation dominated by lupines occurring on mountain slopes with a mean vegetation height of 11cm; and overwintering habitat, which is characterized by a gravel and duff substrate that occurs on the margins of old forest with a mean vegetation height of 3cm. The current management practice of fencing toad breeding pools in meadows may actually increase the impact of cattle grazing on B. canorus terrestrial foraging habitats, thereby having a greater impact on long term population viability, which is a classic example of well intended management practices failing to protect species due to the absence of adequate knowledge of the specialized habitat needs of amphibians. This study suggests the need for a B. canorus core habitat protection zone that extends 500m from the center of all actively used breeding pools.