Feeding habits of the weasel Mustela nivalis in relation to prey abundance.

Feeding habits in the field were examined by scat analysis. Experiments were carried out in an enclosure simulating natural habitats and containing prey species. Microtus agrestis L. was the staple food; other small rodents and lago-morphs were of secondary importance, and shrews, birds and lizards were occasionally taken. Small-rodent populations were exploited in proportion to their numbers, as the various flight reactions of the different prey species were, on the whole, more or less equally effective and the species were not subjected to descriminate hunting. Shrews were little depredated due to the weasels' distaste for them; the weasels also showed little interest in them when hunting. Food segregation between males and females was pronounced when basic food became scarce, causing males to swich to alternative prey. Segregation reflects the different body size and different hunting behaviour in males and females, and food segregation might be important due to the high food requirements of the weasels. Excess of males in decreasing weasel populations can be explained by their superior ability in hunting and in exploring alternative prey. [ABSTRACT FROM AUTHOR]