NOTES ON THE FOOD-HABITS OF COLUBER-HIPPOCREPIS-NIGRESCENS FROM PANTELLERIA ISLAND - A SNAKE THAT FEEDS ON BOTH CARRION AND LIVING PREY

The food habits of Coluber hippocrepis nigrescens, a colubrid snake en demic to the island of Pantelleria in the southern Meditteranean Sea, were studied by means of both stomach contents and faecal analyses. Sn akes preyed only on vertebrates, and most of the prey eaten were roden ts (especially Rattus norvegicus). Ingested biomass per snake averaged 55.63+/-48.94 g (range: 8 - 131 g), i.e. about 28.5% of the average s nake mass (195.18+/-65.61 g; range: 39-277 g). Log prey mass and log p redator mass were positively correlated. The prey mass to predator mas s ratio was not significantly correlated with log predator mass. 36.36 % of the prey found in C. hippocrepis stomachs was eaten by snakes whe n it was already carrion, as demonstrated by the presence of abundant flesh-fly larvae in rats regurgitated by snakes. This is a very unusua l foraging mode for snakes, which are known as active predators feedin g on live organisms. We hypothesize that this unusual foraging mode is an adaptive strategy depending on (1) low level of food availability and (2) high abundance of dead prey, on this arid Mediterranean island .