CANCELLED - The covariant effects of microclimate and microhabitat factors on turtle basking behavior in Waco Creek, Texas

Background/Question/Methods

This study examines how environmental factors influence emydid turtle thermoregulation.  Many emydid freshwater turtles bask, sunning themselves on logs to boost core temperature and raise metabolic rates—often vying for prime sites.   This competition causes both temporal climate and spatial habitat-based selection for optimal basking along a population gradient of small, carnivorous juvenile to large, herbivorous adult turtles, whose shifting mass and metabolic requirements entail different criterion.  However, climate and habitat are rarely linked as potential, covariant factors driving ontogenous basking behavior.   Research goals include examining both the individual and covariant affects of microclimate and microhabitat variables on ontogenous turtle basking behavior.

This experiment was conducted in a wetlands adjacent pool containing 12 turtles individually housed within 12 square floating cages rotated at 10-day trials.  A basking platform was bolted to each cage and thermocron affixed to each turtle’s shell.   Since each cage used a PVC float, floating aquatic vegetation could be regulated and six cages grew a vegetative mat and six cages kept clear.  Wooden basking platform surfaces were faced with either white or black netting.  During each trial, shell, water, basking platform, and air temperature;  short wave radiation; precipitation; and wind speed were assessed at 900 second intervals.   

Results/Conclusions

An ANCOVA linear regression analysis with Bonferroni posthoc was conducted comparing the affect of climate and microhabitat on basking events as expressed by a turtle basking thermoregulation efficiency index and turtle basking density, using ontogenous size classes as a grouping factor.   Turtle basking density showed greater variation and utility than the thermoregulation index.  While several continuous climatological variables evinced significant shift in basking density (i.e.  air temperature and short wave radiation) which mirror trends in the literature, however neither climate or habitat group segregation occurred along the maturity divide and further modeling is required to improve the basking thermoregulation index.