Meeting Abstract
Baseline circulating corticosterone impacts a variety of traits related to locomotor behavior, including glucose mobilization, skeletal muscle function, and probably motivation for activity. Variations in circulating corticosterone levels have likely implications for both individuals and populations, yet the ultimate reason for this variation is unclear. We attempted to manipulate the corticosterone levels of free-living Desert Iguanas (Dipsosaurus dorsalis) as part of a series of studies exploring the relationships between baseline corticosterone, endurance, and home range size. Previous observational work on this population has shown a significant positive correlation between endurance capacity and home range size. For the present experiment, 40 desert iguanas received abdominal corticosterone or saline implants in April 2017 and were released back into the population at point of capture. Endurance capacity was measured twice during temporary (< 1 day) captivity. Individual locations were recorded May-July (via visual recognition) for home range evaluation. First endurance measurements occurred an average of 32 days ± 8 after surgery (SD; range = 17-58 days); mean endurance in the first trial was 7.16 min ± 4.8. Second endurance measurements were taken an average of 44 days ± 14 after surgery (SD; range = 24-73). Mean second endurance trial was 9.11 min ± 7.26. No significant effect of implant type was found for either first (n = 29; p > 0.5) or second (n = 30; p > 0.1) endurance. Mean home range size was 485 m2 ± 282 (SD; range = 90-1,057) and lizards with corticosterone implants tended to have larger home ranges (N = 22; p < 0.1). Forthcoming results will provide hormone levels as context and will incorporate data on relevant ecological factors and estimates of reproductive success.
