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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.
The seasonal feeding habits of the red fox Vulpes vulpes (Linnaeus, 1758), the stone marten Martes foina (Erxleben, 1777), the stoat Mustela erminea Linnaeus, 1758, the badger Meles meles (Linnaeus, 1758) and the otter Lutra lutra (Linnaeus, 1758) were studied in south-west Hungary, in the course of four years. The habitat conditions, because of human influences, were different in the first and second two years. Diet was examined by scat analysis (238, 262, 67, 50 and 1033 samples, respectively). Small mammals, mainly rodents, were the most important prey for foxes, stone martens and stoats in winter and spring. In summer and autumn insects and fruit were added to fox and marten diet, while birds were added to stoat diet. The badger's main food resources were invertebrates (mainly insects) and maize and, in autumn, rodents. Domestic animals (mainly poultry and rabbit) occurred in the diet of the foxes and martens in all seasons, carcasses (mainly Cervidae) in the diet of these predators and in that of the badgers. The predominant prey of otters was fish, but when the abundance of fish declined, the consumption of amphibians increased. Predation on game birds and hare was not significant. In all seasons, niche overlap was high between foxes, martens and stoats. Niche overlap between these species and the badger increased from spring to autumn. Niche overlap between terrestrial predators and the otter was low. The diet of predators were different between the 1st and 2nd periods.
Lutra lutra, Mustela vison, M. putorius, M. erminea, M. nivalis, and the settle­ments of Castor fiber were surveyed along 170 km of rivers in Białowieża Primeval Forest (Poland and Belarus), the best preserved temperate lowland forest in Europe. The censused rivers varied from very small (1-5 m wide, < 1 m deep) to medium-sized (11-15 m wide, up to 3 m deep). Mustelids were counted by tracks left in snow. Mean index of abundance of otters was 2.2 inds/10 km of the river bank (range 0-5) and that of mink 4.6 inds/10 km (range 0-7.5). On average, 1.4 polecats/10 km were recorded (range 0-5). Otters and mink were most abundant on the medium-sized rivers and least numerous on very small ones. Polecats lived predominantly on very small rivers. Species structure of a predator guild varied with river size. On average, 5.1 stoats and 4.0 weasels were counted per 10 km of river bank. Stoats were twice as common along rivers with open marshy flood-plain as along rivers with forested valleys. On average, 2.9 beaver settlements were recorded per 10 km of river bank (range 0-5). Habitat niche overlaps were highest between otter and mink, and stoat and mink. The smallest overlaps were between the polecat and all other predators. Densities of mustelid predators and beavers in Białowieża Primeval Forest were similar to those in other fairly well preserved woodlands in Europe,
Amphibians were important prey to the European mink Mustela lutreola, the American mink M. vison, polecat M. putorius, river otter Lutra lutra, and badger Meles meles, and formed a minor component of the food taken by stoat Mustela erminea, weasel M. nivalis, and pine marten Martes martes. Mink and otter strongly selected for frogs Rana spp. and avoided toads Bufo spp. However, the common toad can be an important prey for semiaquatic mustelids under unfavourable feeding conditions. Toads (mainly Bufo bufo, and rarely B. viridis) also occurred in significant numbers in the diets of polecats and badgers, which seemed to prey on frogs and toads with no clear selection.
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