Retro-orbital blood sampling elicits short-term reductions in feeding behavior in western fence lizards (Sceloporus occidentalis)

Retro-orbital blood sampling, a method where the retro-orbital (post-orbital) sinus is punctured to draw blood, is often used in herpetological research given its ease, speed, and presumed minimal negative effect on the subject. Although literature establishing the method claims little to no impact on subjects, there exists little data explicitly testing the behavioral or welfare-related effects of this technique. We conducted a field experiment with western fence lizards (Sceloporus occidentalis) to address the potential impacts of retro-orbital blood sampling. Whereas handling the lizards had no demonstrable impact on lizard prey capture and feeding, there were significant short-term increases in time to initiate prey attack (attack latency) and time to successfully capture prey (feeding latency) in S. occidentalis immediately following blood draws. These increases diminished within 24 hours. Our experiments provide new evidence that this common blood sampling method reduces lizard feeding efficiency in the short-term. Researchers and welfare advocates may consider incorporating these findings into their research designs to optimize animal welfare and the generation of reliable ecological and behavioral data.