Intraspecific competition, not predation, drives lizard tail loss on islands.
Tail autotomy is mainly considered an antipredator mechanism. Theory suggests that predation pressure relaxes on islands, subsequently reducing autotomy rates. Intraspecific aggression, which may also cause tail loss, probably intensifies on islands due to the higher abundance. We studied whether tail autotomy is mostly affected by predation pressure or by intraspecific competition. We further studied whether predator abundance or predator richness is more important in this context. To test our predictions, we examined multiple populations of two gecko species: Kotschy's gecko (Mediodactylus kotschyi; mainland and 41 islands) and the Mediterranean house gecko (Hemidactylus turcicus; mainland and 17 islands), and estimated their abundance together with five indices of predation. In both species, autotomy rates are higher on islands and decline with most predation indices, in contrast with common wisdom, and increase with gecko abundance. In M. kotschyi, tail-loss rates are higher on predator and viper-free islands, but increase with viper abundance. We suggest that autotomy is not simply, or maybe even mainly, an antipredatory mechanism. Rather, such defence mechanisms are a response to complex direct and indirect biotic interactions and perhaps, in the case of tail autotomy in insular populations, chiefly to intraspecific aggression.
Department of Zoology, Tel Aviv University, Tel Aviv, 6997801, Israel.
Yuval
Y
Itescu
Department of Zoology, Tel Aviv University, Tel Aviv, 6997801, Israel.
Rachel
R
Schwarz
Department of Zoology, Tel Aviv University, Tel Aviv, 6997801, Israel.
Shai
0000-0003-3839-6330
S
Meiri
Section of Zoology and Marine Biology, Department of Biology, University of Athens, Panepistimioupolis, Ilissia, Athens, 157-84, Greece.
Panayiotis
P
Pafilis
D000374:Aggression; D000818:Animals; D020387:Food Chain; D062312:Islands; D008116:Lizards / Q000033:anatomy & histology* / Q000502:physiology*; D008297:Male; D011235:Predatory Behavior; D013623:Tail / Q000033:anatomy & histology*
autotomy; defence mechanisms; geckos; intraspecific aggression; islands; lizards; population abundance; predation pressure