Discipline: Biological Sciences
Shericia Campbell - Virginia State University
Co-Author(s): Victoria Buskey, Virginia State University, VA
If global warming continues to increase temperatures at current rates it is predicted that approximately 60% of Mexican Sceloporus lizard species will be extinct by 2080. The proximate cause for extinctions is that female lizards are spending more time in the shade to avoid overheating. This results in a decrease in foraging time and ultimately a lack of nutritional resources needed for reproduction resulting in a population declines and ultimately extinction. Because ectotherms absorb their thermal energy from the sun, the amount of surface area can play a critical role in its rate of heat gain. Smaller sized individuals have a greater surface area exposed per unit of body mass compared to larger sized individuals. This should result in a more rapid heat gain in smaller sized individuals and subsequently less foraging time. Larger sized individuals with slower rates of heat gain should have increased foraging time and display a reproductive advantage over smaller sized individuals.
Therefore, we hypothesize that smaller sized (mass) lizards exhibiting increased surface area to volume rations will have higher heating gains compared to larger sized individuals with a smaller surface area to volume ratios. We captured lizards by hand from two different populations. A high elevation site, in the Chiricahua Mountains, Arizona, and a low elevation site, in the Sonoita Plain, Arizona. Lizards were transported to the laboratory. Individual snout-vent length data were measured with digital calipers to the nearest 0.01 mm, mass was measured to nearest 0.01 g using an electronic balance. Individual sex and location were recorded. Body (cloacal) and air temperature were recorded using thermocouple probes by placing individuals in a small cylindrical metabolic chamber. The rate of heat gain (oC body/oC air) was determined using the slope of a regression analysis and plotted against the body mass of each lizard. The rate of heat gain showed a significant negative linear relationship to body mass in all lizards (ANOVA: F21,21=7.44, P=0.013) supporting our hypothesis. Future research involves comparing the metabolic costs of increased heat gain for lizards of different sizes and from different locations, and comparison of foraging time between smaller and larger individuals.
Funder Acknowledgement(s): Funding was provided by a National Science Foundation HBCU-UP grant to C. d'Orgeix
Faculty Advisor: Christian d'Orgeix, email@example.com
Role: I participated in all the field work, and data analysis related to this research