Moult and colour change in English weasels (Mustela nivalis)

The moult pattern of the weasel is similar to that of the stoat ( M. erminea ). English weasels rarely turn white in winter but the winter fur is a paler shade of brown than the summer fur.     

Food habits of British stoats (Mustela ermined) and weasels (Mustela nivalis)

Information on the food habits of stoats and weasels was obtained chiefly from gut analyses of carcasses sent from various parts of Britain. Lagomorphs, small rodents and birds form the bulk of the food taken by these predators. The three food classes appear to be equally important to stoats, whereas weasels obtain nearly half of their food from small rodents. Microtus was the most important small rodent in the diet of both stoats and weasels. Game birds were taken more by stoats than weasels; the chief bird prey of the latter was passerines.     

The stoat Mustela erminea population decline in northern Belarus and its consequences for weasels Mustela nivalis

Abstract

In northern Belarus, we have documented a decline in the local stoat Mustela erminea population following the naturalisation of the American mink Mustela vison. The most likely cause is the reduction in the density and distribution of the main prey of stoats, the riparian voles (the water vole Arvicola terrestris and the root vole Microtus oeconomus), due to excessive predation by mink. Since the stoat population has declined, the number of weasels Mustela nivalis in marshlands has increased and their mean body mass has increased, correlated with the higher number and mean weights of rodents available for weasels in marshland compared with forest habitats.     

The food of weasels (Mustela nivalis) on farmland in north-east Scotland

Little is known of the foods of weasels ( Mustela nivalis ) in farmland in Scotland. Data on their diet were collected from two such areas in east Aberdeenshire between 1971 and 1973. A total of 264 samples of scats were analysed, including 236 from live-trapped weasels, and the gut contents from 82 weasel carcasses were also examined. Small rodents, particularly Microtus , were the principal prey, but lagomorphs, birds and insectivores were also eaten. Seasonal variations in the diet were influenced by the availability of prey. Weasels ate very few Clethrionomys although they were common on one study area. Significantly more lagomorphs were identified in scats collected in the morning than in the evening, but no such differences were found for other prey.     

The effects of the nematode parasite Skrjabingylus nasicola on British weasels (Mustela nivalis)

Adult worms of Skrjabingylus nasicola are found in the nasal sinuses of mustelids, and when numerous may cause considerable distortion of the frontal bones. A heavy infestation is commonly assumed to be detrimental to the individual and possibly also to the population. To examine this belief, the frequency of occurrence ("incidence") and extent of damage caused by S. nasicola were analysed with respect to the climate of seven sample areas and the age, sex and body size of 614 British weasels. Incidence ranged from 69–100% of the sample, and mean skull damage from 31 to 53 on an index scale of 0–8 points. Significant correlations were found between incidence and date of collection of young weasels, and between extent of damage and mean number of rain-days in the area. Male weasels were more badly damaged than females, though incidence was the same in both sexes. There was no evidence that badly damaged weasels were smaller, lighter, leaner or died sooner than lightly or undamaged ones, nor that, in the wild, they were infested by eating shrews.     

Effect of the odour of weasels (Mustela nivalis L.) on trapped samples of their prey

Summary The presence of weasel anal gland secretion on rodent live traps substantially depresses population estimate by greatly reducing the catch of Microtus agrestis. The catch of Apodemus sylvaticus remains almost unaffected.     

Functional response of the least weasel, Mustela nivalis nivalis

We investigated the functional response of the least weasel ( Mustela nivalis nivalis ) in a series of experiments conducted in large outdoor enclosures (0.5 ha). Radiocollared Microtus voles were released in the enclosures at different densities (4, 8, 16 and 100/ha) three days before the release of a radiocollared weasel. During the three-day experiment every vole killed was replaced with another one as soon as possible to retain constant prey density. The results demonstrated type II functional response with the predation rate reaching 50% of the asymptotic rate at a vole density of 15 individuals per ha. More voles were killed at the highest densities than would be expected from the known energy demands of weasels. Female and male voles were killed in proportion to their abundances in the enclosures, and no difference in predation risk was detected between voles released in the enclosure before the weasel (residents) and during the experiment (transients).     

The diet of weasels (Mustela nivalis vulgaris) from Purerua Peninsula,Bay of Islands,New Zealand

We studied the diet of weasels (Mustela nivalis vulgaris) caught on Purerua Peninsula, Bay of Islands, by examining gut contents of 16 individuals caught between 2011 and 2012. Mammals were the prey group most consumed by weasels, when measured both as frequency of occurrence and dry weight. In addition, weasels consumed introduced birds, native invertebrates and reptiles, including the endemic copper skink (Oligosoma aeneum), supporting previous studies and suggesting that weasels have greater effects on biodiversity losses than previously acknowledged.     

Climate and refugial origin influence the mitochondrial lineage distribution of weasels (Mustela nivalis) in a phylogeographic suture zone

Overarching trends can be seen in European mammalian phylogeography, yet it is clear that species responded differently depending on adaptations to past environments. We built upon previous work on the phylogeography of weasels (Mustela nivalis) in Europe by using well‐preserved museum specimens from a proposed phylogeographic suture zone. The complete cytochrome b gene was amplified from 49 individuals from present‐day Poland and analyzed with previously published data on a European scale to identify glacial refugia and infer recolonization processes. Bayesian coalescent analysis revealed the importance of the Last Glacial Maximum and the Younger Dryas in the diversification of, and demographic changes in, identified mitochondrial lineages. Our analysis, in conjunction with the available fossil data, strongly points to a Carpathian origin for one of the lineages, and further highlights the importance of this region as a refugium for European mammals. Mustela nivalis originating from this refugium appear to have a selective advantage over M. nivalis from other lineages in certain environments in the suture zone in central Europe, with climate clearly influencing the distribution of mitochondrial DNA lineages. This has important implications not only for our understanding of how past climatic events shaped the genetic architecture of species, but also how they will respond to current and future climatic changes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 57–69.     

On co-existence,foraging strategy and the biogeography of weasels and stoats (Mustela nivalis and M. erminea) in Britain

Summary Mustela nivalis and M. erminea, two sympatric species of weasels of superficially similar appearance and habits, have different breeding and foraging strategies associated with the difference in their body size. M. nivalis is more efficient in exploiting small rodent prey, and can breed rapidly to take immediate advantage of rodent peaks, but is vulnerable to local extinction during rodent declines. M. erminea has more generalized food habits, and is the larger and probably the dominant species, but is limited by delayed implantation to producing only one litter a year. M. nivalis is therefore superior in exploitation competition, and erminea in interference competition. We offer the hypothesis that the co-existence of the two species is permitted by a balance of these competitive advantages determined, at a given time or place, by the heterogeneity of the environment and the distribution of the prey fauna. We use this hypothesis to explain cases where co-existence has either broken down or is not recorded (the results of simultaneous introductions to New Zealand and Terschelling Island, and of myxomatosis in Britain, and the distribution of nivalis and Erminea on the offshore islands of Britain). We argue that the diversity and size distribution of the prey fauna of an island (which are both related to its area and isolation) are important in deciding the species and size of mustelids surviving there; for example, we suggest that nivalis was present in Ireland in immediate post-glacial times but became extinct with the lemmings.     

Population biology of the weasel Mustela nivalis on British game estates

The mean year-class ratio in 6 samples of weasels (total n = 477) ranged from 59% to 84% young, and mean age from 0.79 to 1.16 yr. There was no difference in age structure between samples from 5 game estates and 1 reserve. Mean annual mortality of weasels of both sexes and all ages was 75-90%. In 12 pregnant weasels the mean number of embryos, observed from April to June, was 5.6. There was a definite anoestrous season in winter. Records of the number of weasels killed on game estates show that weasels and stoats reacted differently to the first outbreak of myxomatosis in England in 1954; and that weasel populations are capable of enormous sudden increases (usually associated with "mouse years"). These increases are probably due largely to summer litters produced by precocious juveniles, and also to some adults breeding a second time (both possibilities confirmed from ovarian histology on this material). Traditional gamekeeping practice may influence the seasonal pattern of mortality of weasels (highest in spring) but its effects are probably short-lived.     

On the occurrence of the Weasel,Mustela nivalis,in Turkey

Abstract

It was shown that the Weasel is distributed over the whole of Anatolia The species’ considerable size, the occasional occurrence of a white winter coat and the existence of two types of Weasels (nivalis type and minuta type) in Turkey have often lead to the wrong assumption that the Stoat (M. erminea) also occurs in Turkey.