1 1Section of Human and Animal Physiology, Department of Biology, University of Athens, Panepistimiopolis, 157-84 Athens, Greece
2 2Section of Human and Animal Physiology, Department of Biology, University of Athens, Panepistimiopolis, 157-84 Athens, Greece
3 3Section of Human and Animal Physiology, Department of Biology, University of Athens, Panepistimiopolis, 157-84 Athens, Greece
4 4School of Natural Resources and Environment, University of Michigan, Dana Building, 430 East University, Ann Arbor, MI 48109-1115, USA, Modern Greek Program, Department of Classical Studies, University of Michigan, 2160 Angell Hall, 435
S. State, Ann Arbor, MI 48109-1115, USA;, Email: email@example.com
Caudal autotomy, the self-induced tail shedding from the body, is a common defensive strategy in lizards. Tail loss is followed rapidly by regeneration, revealing the importance of a fully functional tail. Predation pressure has been traditionally correlated with autotomy performance. However there is a lack of evidence regarding the impact of predation regime on tail regeneration. Another important factor that has been neglected is the population density. Though it is well established that crowding alters various life-history traits, the impact of density on caudal regeneration remains understudied. In this paper we compared three island populations of the Aegean Wall Lizard (Podarcis erhardii) that have evolved under different levels of predation pressure: whereas the Naxos population is exposed to numerous predators the Kopries and Daskalio islet populations experience low predation pressure. To evaluate the effect of density-induced stress on caudal regeneration, lizards were treated under two conditions of housing, in single and crowded (six individuals) terraria. Tail sheding occurred prior to this treatment following a standardised method. The length of regenerated tail was recorded weekly. Regeneration rate was higher in single terraria when compared to crowded, reflecting the negative impact of crowding. However we failed to detect any statistically significant difference between single and crowded terraria in the case of Naxos. We believe that the underlying reason must be the heavy predation pressure under which rapid tail regeneration, even under unfavourable conditions, is crucial for survival. It seems that the imperious need for regeneration counteracts density-induced stress.