Meeting Abstract
Most chelonians are slow-moving, herbivorous vertebrates that rely on brightly colored plants to obtain their nutritious requirements. As a result, coevolution with their plant foods has been suggested as a potential cause for a trade-off between visual and olfactory acuity (i.e. influencing the ability to find food items at close vs. long range by using both color and smell). While recent studies have emphasized the chemosensory abilities of reptiles, some studies have also shown that in addition to specialized chemosensation through large olfactory bulbs & the vomeronasal organ, many reptiles may also have a 4th cone in their retina to be able to see in the ultraviolet spectrum of color as well (e.g., red-eared sliders) and behaviorally prefer UV signals. In this study, we assessed UV behavioral preference in gopher tortoises (Gopherus polyphemus) through the use of cardboard discs in a paired choice experiment [Treatment 1: orange disc with spectra peak between 700-850 nanometers (nm) and Treatment 2: orange disc with spectra peak between 700-850 nm and UV peak between 200-300 nm]. Because visual recognition is immediate, initial contest analysis via chi-squared analysis indicated a significant effect of first choice for the UV disc (p=0.004), regardless of randomized presentation to either sex. Additionally, a Poisson distribution of raw numbers of different behaviors also indicated a preference for the UV treatment (p=0.011). Finally, after performing a principal component analysis, principal component 1, including behaviors of sniffing, head extension, and biting/rubbing the disc, significantly differed in preference for the UV treatment (p=0.02), regardless of sex (p=0.1). This is the first study to indicate a behavioral preference for visual signals in the UV for gopher tortoises.
