CHANGES IN PREY SIZE PREFERENCES DURING SUCCESSIVE STAGES OF FORAGING IN THE MEDITERRANEAN WATER SHREW NEOMYS ANOMALUS

Abstract

AbstractPrey size preferences in successive stages of foraging of Mediterranean water shrews Neomys anomalus Cabrera, 1907 were investigated in a terrarium. Seven shrews were tested individually in five experimental variants (simulating different habitat conditions) totally for 504 hours. Water shrews displayed partial preferences for prey size but they were selective from the very beginning of the foraging period. When searching for food, N. anomalus preferred big food portions, abandoning significantly more small than big portions. This tendency was especially strong when few food portions were available on land and there were no natural structures in the terrarium. Selection of big portions was intensified probably by their easier detection. Shrews hoarded proportionally more big than small portions in the scattered hiding-places. This tendency was intensified by the presence of natural structures, dispersion of food and reduction of food quantity placed on land. Later, however, more small than big food portions were eaten, apparently because small portions were easier to manipulate. Scattered food hoarding and preference of large prey are proposed to be the strategy of N. anomalus to maximise the energy net gain and minimise the predation risk and competition for food.