Weasel Mustela Nivalis Research Articles

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

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.

Food habits of stoatsMustela erminea and weaselsMustela nivalis in Denmark

StoatsMustela erminea Linnaeus, 1758 and weaselsMustela nivalis Linnaeus, 1766 exploit the same array of prey species at different frequencies according to body size. The rabbitOryctolagus cuniculus, which typically is the dominant prey for stoats in temperate parts of Europe, is absent in Denmark. The present study based on gastrointestinal tract contents examines the food habits of sympatric stoats (n=112) and weasels (n=132) from Denmark. Rodents were the most important prey group for both stoats and weasels, constituting 77% and 84% of their diet respectively, expressed as frequency of occurrence. No differences were detected in the proportions of major prey groups between sexes within species, but between species the diets differed. Stoats ate birds and birds’ eggs more often than weasels did, while weasels ate more insectivores. Stoats ate more oftenMicrotus voles and water voleArvicola terrestris than weasels did, while weasels ate more bank voleClethrionomys glareolus and moleTalpa europaea. There was a larger dietary overlap between sympatric stoats and weasels in Denmark than in other dietary studies in areas where rabbits were available.

Survival Through Bottlenecks of Vole Cycles: Refuge or Chance Events?

In small rodent populations with wide-amplitude fluctuations and low-density bottlenecks, the individuals that survive through the bottlenecks may gain major fitness advantages as they will be the founders of the following population expansion. Most hypotheses assume that there exists a physical or behavioural refuge from increased predation risk, and that the survivors are most likely individuals adapted to use such refuges. A recent hypothesis suggests that survival probability is habitat-dependent so that some otherwise sub-optimal habitats provide a spatial refuge from predation risk by the main predator(s). We used spatially replicated long-term (1981–2004) trapping and tracking data of voles (field vole Microtus agrestis and sibling vole M. rossiaemeridionalis) and their main predators (weasel Mustela nivalis and stoat M. erminea) to test predictions based on this hypothesis. We did not find support for the hypothesis. We did not find marked phase-dependent differences in the habitat-level distribution of Microtus voles. Habitat types with low Microtus vole abundance had, on average, comparable predator activity than the main Microtus vole habitats, indicating that there were no habitat-level refuges from predators. There appeared to be no permanent site-level refuges: the spatial distribution of voles varied from one bottleneck to another. This suggests that survival through bottlenecks is at least partly determined by chance events. We propose that in this kind of systems, where relatively short-lived prey are hunted by nomadic or widely ranging predators, short-term anti-predator responses may increase survival prospects as efficiently as more costly anti-predator adaptations, and there is no apparent need to maintain special adaptations to bottleneck situations that occur at infrequent intervals.

Survival and behaviour of captive‐born weasels (Mustela nivalis nivalis) released in nature

AbstractThe behaviour and survival of captive‐born least weasels Mustela nivalis nivalis released in nature were reported in this study. Altogether 27 captive‐born and six wild‐caught weasels were equipped with radio transmitters and their survival was studied as a function of age and season. The daily mortality rate was generally higher in captive‐born than in wild‐caught weasels. The survival of captive‐born weasels was highest if they were released during the summer and hence when they were young. Differences in the behavioural patterns of captive‐born and wild‐caught weasels were apparent. Captive‐born weasels were often more visible in the field and were less timid than wild‐caught weasels. Results suggest that to be successful, restocking of weasels should be done with young animals, which are preferably released during the season with abundant food resources.

Summertime activity patterns of common weaselsMustela nivalis vulgaris under differing prey abundances in grassland habitats

WeaselsMustela nivalis Linnaeus, 1766 in Kielder Forest, UK showed a diurnal rhythm of activity in summer and we argue that this is the prevailing rhythm found in weasels under natural conditions. Climatic conditions influenced weasel activity with weasels decreasing activity under rainy conditions, but we found no influence of month or weasel weight. In certain habitat types levels of weasel activity increased with increasing field voleMicrotus agrestis density. This result stands in contrast to results from studies carried out in the laboratory and may reflect a greater proportion of time spent in reproductive activity and intra-specific interactions in areas where vole density, and hence conspecific density is high.

Video monitoring of shrub-nests reveals nest predators

Capsule Jays Garrulus glandarius are the most common predators, but carnivorous mammals and some other species also predate nests. Aim To uncover the mechanisms and consequences of nest predation. Methods I used video-recording equipment to record the fates of 132 nests of Blackcap Sylvia atricapilla over a three-year period. An additional 69 nests without video-recording equipment were monitored for comparison. Results I found a total of 11 species depredating eggs and young of Blackcap. The main predator was Jay, which hunted during the day and was responsible for 21% of nest fates and 46% of nest losses. Many other predators were recorded, mainly carnivorous mammals (Stone Marten Martes foina, Red Fox Vulpes vulpes, Least Weasel Mustela nivalis), which hunted from dusk until dawn and accounted for 25% of nest losses. Wild Boar Sus scrofa and Tawny Owl Strix aluco also predated nests. Whereas mammals needed up to 15 minutes at a nest to consume nest contents, Jays stayed only a few seconds to remove eggs or young, often taking them one by one. When scared off, adults returned to the nest within 15 minutes. Nests were abandoned if only one egg or no young were left and the adults spent up to nine hours and 12 visits before abandoning the nest completely. The overall impact of the video equipment on nest success was low. Conclusion This study underlines the potential of video recording in science and management and the method is recommended for studies on other open-cup-nesting songbirds.

Do breeding Ural owls Strix uralensis protect ground nests of birds?: an experiment using dummy nests

Predatory birds were formerly suggested to have only negative effects on the breeding success of other birds that breed in the vicinity of their nests. However, the predator may also protect these breeding birds by chasing away other nest predators whilst either defending its own nest or by eating other predators in its territory. Ural owl Strix uralensis is known to be an aggressive nest defender. Although its diet mainly consists of voles, it also preys upon bird species (e.g. Corvidae) and even weasels Mustela nivalis, particularly when the vole densities are low. We carried out a dummy nest experiment on six Ural owl territories in central Finland to study whether Ural owls affect the nest predation rates of ground nesting birds. We found that although dummy nest predation differed between Ural owl territories, in every territory the predation risk was lowest in close proximity to Ural owl nests. The protecting effect of the predator continued for a distance of up to several hundred metres from its nest; a much further distance than could be expected if the effect was due solely to the defence of its own nest. Consequently, as suggested for other predatory birds, it may be that breeding Ural owls influence the bird community both directly by predating upon some species and/or indirectly by providing protection for other species. However, natural evidence on breeding habitat selection and predation risk of ground nesting birds should be obtained before detailed inferences on the effects of Ural owl nests on bird community levels are made.

Reproduction of the least weasel in captivity: basic observations and the influence of food availability

The least weaselMustela nivalis nivalis Linnaeus, 1766 is unique among carnivores because of its small body size and capacity for fast reproduction. It has been suggested to be the main agent for maintaining cyclic fluctuations in northern vole populations, largely based on its high reproductive potential and dependence on small rodents. This study describes basic reproductive data on the least weasel obtained during a captive breeding program. In the experiments, food availability was manipulated at the onset of breeding. Altogether, 65 litters were born during the 5-year study. The mean litter size was 5.1 (in 53 litters of known litter size), the most common litter size being six. The sex ratio of weaned young was not biased from 1∶1. The median date of birth was June 4. Food manipulations did not affect mating frequency suggesting that the observation of failure in breeding in years of low abundance of small mammals is due to mortality of embryos or young before weaning, but not due to avoidance of breeding at low food availability. In this respect, weasels differ from other main vole predators, owls and raptors, which often skip breeding if small mammals are scarce.

Estimating weasel Mustela nivalis abundance from tunnel tracking indices at fluctuating field vole Microtus agrestis density

Quantifying the abundance of small mustelids is important both for conservation purposes and for our understanding of ecosystem processes. Footprint tunnel tracking is one of the techniques now used to index the relative abundance of small mammals; however, there have been few or no previous attempts to calibrate indices of mustelid abundance derived from footprint tunnel tracking. Weasel Mustela nivalis abundance was assessed by footprint tunnel tracking and simultaneous live‐trapping, either capture‐mark‐recapture or removal, in six sites in northern England from April 1998 to February 2000. The number of tunnels with weasel footprints was tightly related to the number of weasels live‐trapped, although, as expected, the relationship varied with field vole Microtus agrestis density and season. Temperature had only a weak effect in the calibration. The same number of tunnels with weasel footprints was equivalent to greater weasel abundance at high vole density than at low vole density. Similarly, weasel abundance was greater for the same number of tunnels with weasel footprints in summer and autumn than in winter and spring. In conclusion, it is important to correct for variation in vole density when using activity indices such as footprint tunnel tracking to sample weasel abundance, otherwise spurious patterns may emerge from the use of such index data.

Amplification of DNA markers from scat samples of the least weaselMustela nivalis nivalis

To test the feasibility of using field-collected scats as a source of DNA in the study of the least weaselMustela nivalis nivalis Linnaeus, 1766, DNA was extracted from scat samples collected from captive weasels using a modified extraction protocol. Using universal primers, the control region of the mitochondrial genome was successfully amplified from scat-extracted DNA. This amplification resulted in two products; one equivalent in size and sequence to the product obtained from tissue-extracted weasel DNA, and the other slightly larger and equivalent in size and sequence to the domestic house mouseMus musculus, the food source of the captive weasels. This demonstrates the reliability of DNA extraction from scats, as well as the possibility, under favourable circumstances, of identifying the prey species from the same samples. In addition, we attempted to amplify microsatellite loci from both tissue and scat-extracted DNA using six primer pairs designed for other mustelids, the American minkMustela vison and the wolverineGulo gulo. While three loci, Mvi57 (American mink), Ggu216 and Ggu234 (wolverine), were found to be polymorphic in the least weasel, amplification of these loci from the scat extracted DNA was only successful for approximately half of the samples. Although further work is needed, the present results suggest that it is possible to use scats as a source of DNA in field studies of the least weasel.

Phylogeographic Variation in Two Mustelines, the Least Weasel Mustela nivalis and the Ermine M. erminea of Japan, Based on Mitochondrial DNA Control Region Sequences

Abstract The least weasel Mustela nivalis and the ermine M. erminea of Japan are considered relicts of the last glacial period. To study phylogeographic variation in these mustelines, fragments of the mitochondrial DNA control region were sequenced. In both species, the control region included tandem repeats of 10base motifs at the 3′ portion specific to the genus Mustela. Phylogenetic trees of the 5′ portion (581–584 bases) of M. nivalis indicated that haplotypes in the Hokkaido population clearly diverged from those in the Honshu population. Geographic pattern of intraspecific variations illustrated by this result is concordant with that by the result of a previous cytogenetic study, which revealed the karyotypic differentiation between the two populations. These findings might suggest that the Hokkaido and Honshu populations of M. nivalis were geographically isolated in advance of the formation of the Tsugaru strait between Hokkaido and Honshu. Distribution pattern of the mitochondrial DNA haplotypes w...

Geographical variation in genet (Genetta genetta L.) diet: a literature review

AbstractThe geographical variation in the Genet Genetta genetta L. diet was analysed from 12 locations covering its entire range. Data were obtained from the available literature on food studies in this species. We studied the general food spectrum of this species and compared the importance of different prey items in each area through PCA analysis. The possible influence of some large‐scale environmental factors (latitude, altitude, Mediterraneity) on diet were studied by means of regression analysis and anova. The study assessed the frequency of occurrence of each prey group and diet diversity. Results show the existence of two ‘food’ groups: (i) Genets which feed on a wide food spectrum, especially arthropods and (ii) Genets which feed on small mammals at a high frequency, while the remaining prey items are scarce or absent. At the intraspecific level, Genets behave as generalist species, with the small mammals (especially, the Woodmouse) as the most outstanding prey item. However, when compared with the diet of other medium‐sized Palaearctic carnivores, we can say that the Genet is intermediate between typical generalists (Martens Martes spp., Red Foxes Vulpes vulpes and Badgers Meles meles) and specialists (Otters Lutra lutra, Stoat Mustela erminea and Weasel Mustela nivalis). Finally, anova shows the existence of a relationship between diet diversity and Mediterraneity (associated with taxa such as arthropods, reptiles and amphibians), but no relationship was found for latitude or altitude. The importance of interspecific competition, based on island data, is discussed.

Anticoagulant rodenticides in stoats ( Mustela erminea) and weasels ( Mustela nivalis) in England

Concentrations of six anticoagulant rodenticides were examined in the livers of stoats Mustela erminea L. and weasels Mustela nivalis L. trapped or shot by gamekeepers between August 1996 and March 1997. Residues of rodenticides were detected in nine out of 40 stoats (23%) and three out of ten weasels (30%) from five out of eight estates in central and eastern England. Bromadiolone (0.04–0.38 mg kg −1 wet wt) was detected in three stoats and one weasel, coumatetralyl (0.0085–0.06 mg kg −1) in six stoats and three weasels and brodifacoum (0.12 mg kg −1) in one stoat. One stoat and one weasel contained combinations of two rodenticides. Exposure to rodenticides was more prevalent in female stoats than in males. Rodenticides were widely used away from buildings on the sampled estates and so mustelids need not forage around buildings to be exposed. We conclude that stoats and weasels are secondarily exposed to rodenticides mainly by eating non-target species.

EXPERIMENTAL REDUCTION OF PREDATORS REVERSES THE CRASH PHASE OF SMALL-RODENT CYCLES

The mechanisms driving short-term (3–5 yr) cyclic fluctuations in densities of boreal small rodents, and especially, those causing a crash in numbers, have remained a puzzle, although food shortage and predation have been proposed as the main factors causing these fluctuations. In the first large-scale vertebrate predator manipulation experiment with sufficient replication, densities of small mustelids (the least weasel Mustela nivalis and the stoat M. erminea) and avian predators (mainly the Eurasian Kestrel Falco tinnunculus and Tengmalm’s Owl Aegolius funereus) were reduced in six different areas, 2–3 km2 each, in two crash phases (1992 and 1995) of the 3-yr cycle of voles (field vole Microtus agrestis, sibling vole M. rossiaemeridionalis, and bank vole Clethrionomys glareolus). The reduction of all main predators reversed the decline in density of small rodents in the subsequent summer, whereas in areas with least weasel reduction and in control areas without predator manipulation, small rodent densities continued to decline. That only reduction of all main predators was sufficient to prevent this summer crash was apparently because least weasels represent <40% of vole-eating predators in western Finland. These results provide novel evidence for the hypothesis that specialist predators drive a summer decline of cyclic rodent populations in northern Europe.

The breeding biology of the Chiffchaff Phylloscopus collybita in Britain: a comparison of an intensive study with records of the BTO Nest Record Scheme

Most known aspects of the breeding biology of the Chiffchaff come from studies carried out in Central Europe. This study documents aspects of its breeding biology in Britain by comparing data gathered during an intensive study in Wytham Woods (Oxford) from 1992 to 1994, and records from 1933 to 1993 held by the BTO's Nest Record Scheme. Comparison of these two data sets showed close similarities in parameters such as: (1) laying dates; (2) length of the breeding season; (3) nest site usage; (4) clutch size; (5) length of the nestling period; and (6) the relative importance of causes of nest failure. First clutches are laid in the second half of April, and early May, with second clutches in June. Nests are built close to the ground, usually in Bramble bushes (Rubus spp.). Average clutch size decreases from 6 to 4 eggs through the season. Incubation and nestling periods last 13–14 days. Nest losses are mainly due to predation, which accounted for approximately 75% of losses in both data sets, and the Weasel (Mustela nivalis) appears to be the main predator in Wytham Woods.

Prey selection of the least weasel Mustela nivalis in the laboratory

Prey individuals representing the bank vole Clethrionomys glareolus and the field vole Microtus agrestiswere presented in pair to male and female least weasels Mustela nivalis Linnaeus, 1766 in the laboratory. The voles were placed in two radomly selected boxes out of 8 boxes, which were connected to an arena housing the weasel. For each trial we recorded the finding, killing and eating order of the two prey individuals. Male weasels tended to kill bank voles before field voles, and female weasels preffered to eat the bank vole first. Both sexes selected juvenile bank voles as the first prey to eat.

Weasel Population Response, Home Range, and Predation on Rodents in a Deciduous Forest in Poland

Numerical responses of the weasel Mustela nivalis to the changes in population density of forest rodents (bank vole Cleothrionomys glareolus and yellow—necked mouse Apodemus flavicollis) and predation by weasels studied in the pristine deciduous forests of Bialowieza National Park, eastern Poland, in 1985 through 1992. The rodents experienced 5 yr of noncyclic (seasonal) fluctuations (autumn density 23—74 rodents/ha) and 2 yr of outbreak and crash (triggered by synchronous heavy crop of oak, hornbeam, and maple seeds). Autumn numbers of rodents exceeded 300 individuals/ha during the outbreak and dropped to 8 individuals/ha in the following autumn. Weasels were censused by livetrapping in summer and by snowtracking on an 11.2—km2 grid of transects in winter. Radiotracking of 12 weasels in 1990 and 1991 yielded estimates of home ranges and daily movement distances, which were combined with snowtracking and livetrapping data to estimate densities during 7yr. Estimated winter density of weasels varied from 5.2 to 27.3 individuals/10km2 in December and declined to 0—19.1 individuals/10 km2 by early spring (March). Midsummer (July/August) indices of weasel numbers were extremely variable and corresponded to 41.9—47.6 individuals/10 km2 in years with moderate density of rodents, 101.7 individuals/10 km2 during the rodent outbreak and 19.1 individuals/10 km2 during the crash. Increase of weasel numbers from spring to midsummer was positively related to the spring numbers of rodents. Autumn and winter decline of weasel numbers was not related to rodent density changes. During the outbreak and crash of the rodent population, the numbers of weasels and rodents (both sampled at 2—3 mo intervals) were positively correlated (P &lt; 0.0005) with no time lag. Home ranges of male weasels radiotracked during the rodent outbreak were 11—37 ha (minimum convex polygon), compared to 117—216 ha during the crash year. The predator/prey ratio varied from 0 to 2.5 weasels/1000 rodents. The ratio was highest at low densities of rodents. With increasing numbers of rodents, the ratio declined, since rodent population growth was overwhelmingly faster than weasel population growth. In the 7 autumn—winter seasons (1 October—15 April), weasels removed, on average, 1.6 to 9.5 rodents from each hectare, i.e., from 2 to 28% of autumn numbers of rodents. Winter predation by weasels was heaviest at rodent density of °20 individuals/ha. At lower densities of rodents, the number of weasels was restricted by food shortage and the role of their predation rapidly declined. At high rodent densities, the rodent numbers by far exceeded the predatory capacity of weasels and predation percentage declined again. Weasel predation in relation to rodent density has the same pattern in geographic zones ranging from Turkmen deserts to European farmlands and forests.

Summer pelaged weasels in winter: Indication of winter reproduction

Two weasels Mustela nivalis (L.) were observed on April 4 and 18, 1992, respectively, in the western parts of Hardangervidda, southern Norway. The weasels were both in summer pelage (walnut brown above and white below), in a season when the weasel normally has a completely white coat. The first observed weasel was caught, and age-determination showed that it was born during the early winter months. Thus, summer pelaged weasels in winter are a strong indication of successful winter reproduction.

Responses of Bank Voles to Odours of Seven Species of Predators: Experimental Data and Their Relevance to Natural Predator-Vole Relationships

Bank voles Clethrionomys glareolus were exposed to odours of seven species of predators (weasel Mustela nivalis, stoat Mustela erminea, polecat Mustela putorius, stone marten Martes foina, red fox Vulpes vulpes, raccoon dog Nyctereutes procyonoides, and tawny owl Strix aluco) and a non-predatory animal (domestic rabbit) in a total of 48 one-day terrarium trials. In response to odours of each mammalian predator, dispensed in one of the 3 pens, the number of voles utilizing that pen decreased signilicantly (50-90% of initial numbers). Tawny owl and rabbit scents did not change voles' distribution in the terrarium. Bank voles climbed twigs («arboreal» escape) in trials with mustelid (but not canid) predators. Odours of stoat, weasel and marten made the voles stay out of tubes simulating underground tunnels

The effects of harvest on arable wood mice Apodemus sylvaticus

The effects of cereal harvesting on the ecology of wood mice Apodemus sylvaticus were investigated at three arable study sites in Oxfordshire from 1987 to 1991 using both radio-tracking and live-trapping methodologies. The process of harvesting itself had little direct effect on the mice, but the removal of the cover afforded by the crop greatly increased predation pressure on the mice. After harvest, mice either emigrated from the arable ecosystem or reduced activity. Nevertheless, over half (17 of 32) of the mice radio-collared before harvest were taken by predators in the first week following harvest. Together with emigration, this produced an 80% decrease in the population. Post-harvest activities such as stubble burning subsequently further increased mortality. The dramatic increase in prey availability may benefit predators of small mammals in the cereal ecosystem such as tawny owls Strix aluco and weasels Mustela nivalis.