The capture of voles and shrews by male and female ermine Mustela erminea in captivity

The capture of meadow vole Microtus pennsylvanicus and short-tailed shrew Blarina brevicauda by male and female ermine Mustela erminea was observed in an indoor enclosure which simulated field conditions. We made 114 trials using 15 different male and 17 different female ermine. Each trial involved one ermine deprived of food for either 0, 10 or 20 h, and only one individual of either prey species. In most trials, the hunting efficiency (indicated by search and handling durations, and number of captures) of male ermine was greater than that of females. Females hardly ever captured shrews, whereas males hunted them successfully independently of the level of food deprivation. However, when deprived of food for 20 h, females spent less time than males in searching for voles. These results suggest that smaller females may be specialized and more effective at hunting meadow voles than larger males under severe food deprivation. This advantage may allow them to channel a greater proportion of energy into reproduction.