Basking Activity is Modulated by Health State but is Constrained by Conspicuousness to Predators in Male Spanish Terrapins

Aerial basking may have several benefits for freshwater turtles in addition to thermoregulation such as removing parasites from the skin, which would improve health state. However, basking outside of water may be risky because it may expose freshwater turtles to terrestrial predators. Here, we monitored the basking activity of male Spanish terrapins (Mauremys leprosa) in a wild population of the south‐western of the Iberian Peninsula. We also measured body size, health state parameters, parasite prevalence, and limb coloration of these individuals. We aimed to examine whether basking may improve health state of turtles. The results showed that male turtles with higher basking activity were those parasitized by Hepatozoon and that had lower total white blood cell (WBC). This might indicate that turtles in worse health condition increase their time spent basking to improve their immune system. In addition, because basking might be risky, we also expected that turtles with more conspicuous coloration should reduce their basking activity to avoid being detected by potential predators. We found that infected turtles, but not uninfected ones, that spent more time basking also had less bright coloration in limb stripes. Our study provides evidence that basking activity may improve health state of terrapins, but that color conspicuity may increase costs of basking, especially for parasitized individuals. Understanding the balance between the benefits and the costs of basking might be essential for the conservation of freshwater turtle populations.