Eat, Prey, Live: Comparative Thermal Ecology and Energy Requirements of Coastal and Inland Pacific r

Crowell, Hayley

hylacrowe@gmail.com

Taylor, Emily N.

Biological Sciences Department

California Polytechnic State University

San Luis Obispo, CA, USA

Understanding the effects of changing temperatures on ectothermic species is crucial if land managers and researchers are to make informed decisions about how to mitigate the predicted loss of diversity as a result of anthropogenic climate change. Using body temperature data from free-ranging snakes, the field metabolic rates, and therefore basic energetic requirements, can be calculated to determine average annual energy expenditure of a given ectotherm. However, few studies exist that examine the effects of climate across multiple populations within a single given species, especially snakes. The goal of this study is to use field active body temperature data from four distinct populations of Crotalus oreganus from central California (two inland and two coastal) to compare field and preferred body temperatures, estimated metabolic rates and annual energy expenditure across varying habitat types. Snake body temperature data were collected via internal implantation of Thermochron iButton temperature loggers from 2010 to 2017 during the snakes’ active season (April-Oct). Despite dramatically different ambient temperatures at the field sites, snakes at inland and coastal sites thermoregulate such that they experience similar mean daily body temperatures within the same year. However, inland snakes are significantly larger in mass than their coastal counterparts and therefore have higher overall metabolic rates. Operative temperature models were used throughout each of the four field sites in order to characterize microhabitat temperatures available and calculate thermal quality of the landscape. In combination with predicted increases in ambient temperature, probable changes in body temperatures, activity times, and energy requirements were extrapolated for each site through for a 1°C and 2°C increase in ambient temperature.