Lauren Neel and Lance McBrayer
Habitats are being altered by humans at an alarming rate. Climate change, land management, and habitat fragmentation influence the temperatures available in a habitat. Environmental temperatures are especially important for ectotherms, or “cold-blooded” animals, as their physiological rates are sensitive to changes in temperature. For ectotherms, physiological performance will be decreased when they experience temperatures outside their preferred range. Decreased performance can have consequences for an animal’s ability to forage, escape predators, or acquire mates.
Ectotherms may respond to long-term changes in thermal environments in several ways. Behavioural adjustments, such as altering daily activity times, habitat shifts, and changing basking frequency can buffer the temperatures experienced. However, behavioural shifts alone may not be sufficient to buffer unfavourable temperatures. Furthermore, the energetic costs of behavioural thermoregulation may deter such behaviour. Ectotherms may compensate for high cost of thermoregulating by physiologically adapting to novel environmental conditions. Adaptations may include shifting preferred temperatures or thermal optima, such that these thermal parameters align with the temperatures that are available.
In this study we measured how habitat management influences the temperatures available to the Florida scrub lizard in longleaf pine and sand pine scrub forests. Due to logging in sand pine scrub habitats, the temperatures available to the lizards there are much warmer than the temperatures in longleaf pine forests. We quantified the thermal environments and measured several traits associated with thermoregulatory behaviour and physiology to determine how the lizards responded to the environmental change. To determine the physiological responses, we measured critical thermal limits and sprint speed at varying temperatures. We found that lizards from the warmer, sand pine scrub habitats shifted their thermal limits and thermal optima upwards to perform better at the temperatures available to them. In all habitats lizards were found to increase effort in thermoregulatory behaviour more when unfavourably hot, versus unfavourably cold, temperatures were experienced to avoid overheating. In summary, our results show that habitat management can alter the temperatures available to small ectotherms, and thus can have major impacts on thermoregulatory behaviour and thermal physiology.