Movements and habitat utilization of Yosemite toads (Bufo canorus) in the Sierra National Forest, California

Background/Question/Methods: Dispersal is an important ecological process that is central to many questions in both theoretical and applied ecology, including population dynamics (e.g. metapopulations) and conservation biology.  The movement of individuals from one habitat patch to another has significant consequences for the populations of many species.  Despite the importance of dispersal in ecology, there is not much data on the spatial movements of free-ranging individuals in natural landscapes.  I examined movements and habitat utilization of the Yosemite toad (Bufo canorus) in the Sierra National Forest, California in April-August 2007.  Fifteen adult toads were initially captured from two breeding meadows, outfitted with radio transmitters, and tracked as the individuals left the meadows.  Data were collected on the environmental conditions, habitat type, and location for each individual tracked.Results/Conclusions: Toads moved from the meadows into the surrounding mixed-conifer upland habitat and were located in various micro-habitats such as mammal burrows and under logs.  Home range sizes, minimum and maximum distances moved from the breeding site, and differences between male and female toads were calculated.  The majority of toads traveled less than a straight-line distance of 250 meters from their breeding site during the time they were tracked.  Females tended to travel farther and have larger home ranges than males, though the differences were not significant.  One female did travel over 1 km to a meadow where breeding did not occur during the year.  This movement from occupied to unoccupied breeding meadows indicates that metapopulation dynamics are potentially important for the species in this area.