Aggressive interactions and mating in wild populations of the European pond turtle Emys orbicularis

Sexual size dimorphism, aggressive interactions, and mating events were rec orded in two populations of the European pond turtle, Emys orbicularis, in central Italy. Females were significantly larger than males in both populat ions. Fighting between males was observed frequently and ranking the males according to the outcome of hostile interactions revealed consistent quasi- linear hierarchies in both populations. Rank was not related to males mass. Minor aggressive patterns, involving males, females, and juveniles, in bot h populations, particularly during basking. Several males were observed mou nting more than one female, and most females were mounted by more than one male during the same breeding season. No correlation was found between male rank and total number of matings, or total number of females mounted by ea ch male. Social interactions of Emys oubicularis are discussed with referen ce to habitat preference and phylogenetic relationships among emydids.