Dietary patterns of two sympatric Mediterranean snakes (Hierophis viridiflavus and Zamenis longissimus) along a gradient of habitat alteration

The food habits of two species of colubrid snakes (Hierophis viridiflavus and Zamenis longissimus) were studied in three areas in Mediterranean central Italy representing a gradient of natural habitat alteration from a natural mixed oak forest towards an entirely deforested, urban–agricultural habitat. Two diet descriptors were used: 1) total number of prey items eaten by each species in each study area, and 2) number of individual snakes containing a given prey type. Only adults were studied. There was no significant body size difference within species or among sites, and the diets of males and females were similar in both species. Our results revealed that habitat alteration drives some directional changes in the diet composition of these snakes: food niche breadth decreased in the two species from the least to the most altered study area, thus suggesting higher dietary generalism of snakes in natural areas. Food niche overlap values were similar interspecifically and intraspecifically, but tended to increase interspecifically with habitat alteration.