Behavioural response to predation risks depends on experimental change in dehydration state in a lizard

Abstract

Optimal regulation of body temperature and water balance is essential for the survival of terrestrial ectotherms in a changing world. A behavioural trade-off exists between these two constraints because maintaining a high body temperature usually increases evaporative water losses. In addition, the evaluation of predation risk is a key factor in behavioural decision for prey species, and predation threat can cause shift in individual behaviours due to the modification of the cost-benefit balance of thermo-hydroregulation. However, little is known on how prey integrate these different biotic and abiotic stressors when combined. Here, we performed an experimental study on the common lizard, a terrestrial ectotherm prey species, sensitive to water restriction and able to detect specialised predator scents in its environment. We analysed changes in thermo-hydroregulation behaviours, activity patterns and body temperature in response to a chronic water stress coupled with simulated punctual occurrences of predator scents. Water restriction and predator threat had mostly additive effects on lizard thermoregulation behaviour. They both reduced the time spent basking and thermoregulation precision. They also had opposite effects on the time spent active, water restriction reducing activity whereas the presence of predator scents increased it. Yet, we also found an interactive effect on hydroregulation behaviour, as water-restricted lizards showed a wet-shelter preference only in absence of predator odours. This study demonstrates the existence of some hydration state dependent behavioural responses to predator threat and suggests that fear of predators may compromise thermo-hydroregulation and thus prey performances.

Significance statement

In this paper, we show that the fear of predators induces significant changes in the thermo-hydroregulation behaviours of a widespread terrestrial lizard species, some of which are influenced by a physiological increase in dehydration induced by an experimental restriction of water availability. There is a general lack of understanding about how prey respond to simultaneous changes in biotic and abiotic stressors; in particular, our comprehension of the non-energetic costs of thermoregulation caused by the presence of predators and the absence of water in the environment is extremely limited. Our findings indicate that predators have state-dependent effects on the behaviour of their prey and that joint changes in water availability and predation risks can compromise the thermo-hydroregulation strategies of their prey, potentially affecting their physiological performances.