Use of microhabitat and substratum types by sympatric snakes in a Mediterranean area of central Italy

Abstract

The ecological distribution of three snake species (Vipera aspis, Coluber viridiflavus, Elaphe longissima), in relation to microhabitat and substratum type, was studied in a coastal Mediterranean area of central Italy (Castel Fusano Forest, province of Rome), characterized by sandy dunes facing the sea and internal pinewoods. Snake densities varied considerably from spot to spot, but averaged 0.2 specimens per ha for Vipera aspis, 3.5 specimens per ha for Coluber viridiflavus, and 1.5 specimens per ha for Elaphe longissima. Frequency of observations varied significantly among species in the various microhabitats : in general, Vipera aspis and Coluber viridiflavus appeared relatively similar in terms of microhabitat types preference. However, important seasonal variations in the frequency of utilization of the various microhabitats were recorded. All the three species basked primarily upon leaf litter substratum, despite there were some minor interspecific and interseasonal differences. In general, Coluber viridiflavus and Elaphe longissima appeared relatively similar in terms of substratum types preference. However, the three species tended to bask on given substratum types in a way independent from the availability of the given substratum types in the environment. Both in terms of micro-habitat and substratum types utilization, Coluber viridiflavus was the most generalist species, whereas Elaphe longissima was the most specialized species. The ecological reasons for the interspecific differences in the patterns of utilization of the substratum and microhabitat types are discussed in the light of other studies published to date.