Foraging by a threatened species - the white-clawed crayfish, Austropotamobius pallipes.

In analysing the eco-ethological traits of animal populations from the viewpoint of conservation biology, an understanding of the foraging activity of endangered species provides useful clues on habitat requirements and resource utilisation. The present study examined the foraging excursions of 60 specimens of the threatened crayfish, Austropotamobius pallipes, in a stream of central Italy. Foraging activity was related to both the distance travelled and the area covered, as well as to the organic content of the substrates investigated. Results were discussed under the premises of SCHOENER'S (1971) theory of feeding strategies. The white-clawed crayfish minimised the time spent feeding: foraging excursions did not exceed one hour and the range of food search increased with time. Energy and nutrient intake were however maximised: crayfish fed on the substrates having higher organic carbon and nitrogen contents. Inter-sexual food partitioning was shown, males and females mostly feeding on vegetable debris and mosses, respectively. We speculate that this is a mechanism to avoid competition between dominant males and subordinate females.