Movement and habitat use of the Yosemite toad (Anaxyrux canorus) in the Sierra Nevada mountains, California

Background/Question/Methods: Movement information is necessary for identifying animals’ habitat requirements and use patterns. Understanding movement is especially important for species of special concern such as the Yosemite toad (Anaxyrus canorus), whose populations appear to be in decline for unknown reasons. In late spring and summer of 2007-2009, I conducted a study on the movements and habitat use of adult Yosemite toads in the Sierra National Forest, California. Forty-two adult toads were captured from breeding meadows, outfitted with radio transmitters and radio-tracked as they left their breeding sites. I collected data on the location, habitat and microsite type, and environmental conditions for each individual tracked. The aims of this study were to: (1) determine mean and maximum distances traveled by Yosemite toads away from breeding sites; (2) analyze differences in distance traveled by sex and by meadow location; (3) examine microsite usage by Yosemite toads; and (4) examine terrestrial vegetation communities in sites with and without Yosemite toads.

Results/Conclusions: Yosemite toads moved up to 1.26 kilometers away from breeding meadows and the average distance moved was 270 meters. Females moved significantly longer distances than males and had a larger home range.  Distance traveled was related to Julian day as well as the interaction between day and sex. Yosemite toads used terrestrial environments extensively and were found throughout the mixed-conifer forest. Burrows were the most commonly used microsite but other protective cover such as logs, rocks and tree stumps were also used. The locations occupied by Yosemite toads in the terrestrial environment were more open with less canopy and fewer woody species than surrounding areas. The results of this study have implications for identifying population processes such as metapopulation dynamics, as well as for management purposes such as establishing the size of buffer zones and identifying sensitive habitat in the terrestrial environment.