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Jocele P. Wang, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523 USA and Stephen C. Adolph, Department of Biology, Harvey Mudd College, Claremont, CA 91711 USA

Surgically implanted radiotransmitters are often used in field studies of thermoregulatory behavior in reptiles, but little is known about the effects of the surgeries per se. We surgically implanted facsimile radiotransmitters (1.2 g) intraperitoneally into adult male western fence lizards (Sceloporus occidentalis, mean mass = 14.1 g). We used two control groups: anesthesia controls, which experienced the same deep hypothermic anesthesia conditions, and sham-operated, which received surgical incisions and closure but no transmitter implant. We measured body temperature (Tb) selection in laboratory photothermal gradients before and after surgeries. Fence lizards selected Tb's similar to those of active lizards in the field (34-36°C), and near the thermal optimum for several physiological traits. On the first two days after surgeries, lizards with transmitter implants selected Tb's 1.1°C lower than those in the anesthesia control group, whereas sham-operated lizards selected Tb's did not differ among groups. These results suggest that surgically implanted transmitters (and possibly other surgical procedures) may affect behavioral thermoregulation in small lizards for several days after surgeries. However, the effect in these lizards was relatively minor and short-lived.