Non-lethal effects of predators on body growth and health state of juvenile lizards, Psammdromus algirus.

Abstract

Predation risk does not necessarily increase predation rates because prey may be able to behave differentially to cope with higher predation risk. However, antipredatory behaviors may be costly, leading to negative, although non-lethal, effects of predators on prey. We examined in outdoor enclosures whether an experimental increase in predation pressure, which did not increase direct mortality, but forced individuals to increase antipredatory behaviors, may have significant non-lethal effects on body growth and health state of juvenile lizards, Psammodromus algirus. Simulated persistent predator attacks resulted in slower rates of body size growth and body mass gain of juvenile lizards, which may greatly affect their future survival. However, juvenile lizards were able to maintain their initial body condition and immune response regardless of predation risk level. Moreover, our data suggested that experience of lizards with their home range "environment" might allow them to compensate the negative effects of temporal high predation risk on body condition when predation risk subsequently decreased. Finally, juvenile lizards with greater immune responses showed smaller increments in body size, but larger increments in body mass and body condition, at the end of the control treatment. In contrast, there was no relationship between immunity and growth after the experimental treatment.