Cohort variation in the life-history parameters of stoats Mustela erminea in relation to fluctuating food resources:: a challenge to boreal ecologists

This paper reviews field evidence suggesting that periodic temporary population irruptions of feral house mice Mus musculus in New Zealand have a substantial effect on the reproductive success of stoats Mustela erminea Linnaeus, 1758. Stoats born during the summer of a peak in numbers of mice are more numerous and have higher fecundity (ovulation rate) but lower productivity (independent offspring per female) and shorter longevity than those born when mice are not abundant. This reversed silver-spoon effect is apparently correlated with intense competition for food within a much larger than usual cohort of young stoats. However, both stoats and mice are introduced in New Zealand, so it is possible that these effects are not natural. The question could be resolved by data demonstrating similar cohort effects in stoats in the northern hemisphere, living in areas with fluctuating vole populations and limited alternative prey.