Water Vole Arvicola Terrestris Research Articles

Identification of potential chemosignals in the European water vole Arvicola terrestris

The water vole Arvicola terrestris is endemic to Europe where its outbreak generates severe economic losses for farmers. Our project aimed at characterising putative chemical signals used by this species, to develop new sustainable methods for population control that could also be used for this species protection in Great Britain. The water vole, as well as other rodents, uses specific urination sites as territorial and sex pheromone markers, still unidentified. Lateral scent glands and urine samples were collected from wild males and females caught in the field, at different periods of the year. Their volatile composition was analysed for each individual and not on pooled samples, revealing a specific profile of flank glands in October and a specific profile of urinary volatiles in July. The urinary protein content appeared more contrasted as males secrete higher levels of a lipocalin than females, whenever the trapping period. We named this protein arvicolin. Male and female liver transcript sequencing did not identify any expression of other odorant-binding protein sequence. This work demonstrates that even in absence of genome, identification of chemical signals from wild animals is possible and could be helpful in strategies of species control and protection.

СОДЕРЖАНИЕ РТУТИ И АНТИОКСИДАНТНАЯ СИСТЕМА У НАСЕКОМОЯДНЫХ (INSECTIVORA, MAMMALIA) И ГРЫЗУНОВ (RODENTIA, MAMMALIA) РАЗЛИЧНОГО ЭКОГЕНЕЗА

The present study was aimed at analyzing the total mercury in the tissues of mammals adapted to the semi-aquatic or subterranean lifestyle and at analyzing the possible role of their antioxidant system in heavy metal detoxification. The water shrew (Neomys fodiens Pennant, 1771), European mole (Talpa europaea Linnaeus 1758), muskrat (Ondatra zibethicus Linnaeus, 1766), and water vole (Arvicola terrestris Linnaeus, 1758) were the species under study. Our results indicate that the tissue mercury accumulation depends on age, the tissue type and diet of the species. The largest mercury deposition occurred in the water shrew tissues as compared with the other species. Age features of toxicant accumulation in the animals were noted. A correlation between the mercury concentration and the catalase activity in the kidneys of the species investigated was revealed.

Revealing of Natural Leptospirosis Focus in Irkutsk Suburb

For the first time natural leptospirosis focus was revealed in the Irkutsk suburb in 2012 - 2014 during epizootological inspection of a pond-marsh complex. Total 74 small animals (14 species) were examined, specific fragments of Leptospira DNA were found in 16,2%; positive in microagglutination test results were in 1,6% of the samples. Two pathogenic Leptospira strains were isolated from tundra common shrews (Sorex tundrensis) and one isolate - from a water vole (Arvicola terrestris). Circulation of pathogenic Leptospira in a city line represents a potential risk of infection for local population that requires the planning and realization of appropriate preventive actions.

Maturation of cestodes depending on the territorial status and food supply of their host, the water vole (Arvicola terrestris)

Cestodes found in water voles (Arvicola terrestris L., 1758) trapped over six breeding seasons in the same local habitats included the following species: Arvicolepis transfuga (Spassky et Merkuscheva 1967), Paranoplacepala blanchardi (Moniez 1891), P. omphalodes (Hermann 1783), Parandria feodorovi (Gulyaev et Chetchulin 1996), Aprostatandrya dentate (Galli-Valerio 1905), and Arostrilepis microtis (Gulyaev et Chetchulin 2005). The dependence of cestode maturation on interannual variation in the food supply, territorial status, and morphofunctional characters of the hosts was analyzed in the two most abundant species, A. transfuga and P. feodorovi. The results showed that differences in host sex and food supply had no significant effect on cestode maturation. Judging from the proportion of gravid helminths of either species, the rate of their maturation was higher in nonresident than in resident voles. This proportion negatively correlated with body weight of male or female voles. It also negatively correlated with male fecal testosterone level, whereas correlations with fecal protein and progesterone levels were positive. The observed relationships do not explain why the occurrence frequency of gravid cestodes was higher in nonresident water voles, because they either did not differ from residents in parameters relevant to cestode maturation (body weight, fecal protein and testosterone levels) or the difference was opposite in direction (fecal progesterone was higher in resident voles). Nevertheless, an increase in the proportion of gravid cestodes in nonresident water voles may provide for more effective dispersal of these parasites.

Vole pests in apple orchards: use of presence signs to estimate the abundance of Arvicola terrestris cantabriae and Microtus lusitanicus

The sustainable management of vole populations to reduce crop damage requires a reliable estimation of rodent density. The present study was conducted in 2011 in Asturias (NW, Spain) and aimed at developing a method for estimating the density of the water vole Arvicola terrestris cantabriae and the Lusitanian pine vole Microtus lusitanicus in apple orchards based on their presence signs. Previously, as A. t. cantabriae and the Iberian mole Talpa occidentalis occur simultaneously in the same habitats, we had to determine if earth mounds caused by these two species may be accurately differentiated. The results showed that presence signs may be used to discriminate the occurrence of A. t. cantabriae and T. occidentalis in areas of sympatry. The characteristics most interesting for species differentiation were the linear distribution pattern of the mounds and the occurrence of ‘earth sausages’ and ‘earth paths’, all of them typical of moles. The high correlation coefficients (rs > 0.88) obtained between animal captures and the presence of activity signs for the two vole species revealed that it is possible to estimate A. t. cantabriae and M. lusitanicus densities by using the presence signs. An estimating model adapted for apple orchards and for simultaneous sampling both voles is proposed. In addition, we confirmed that the three mammal species coexist frequently in the same orchards. The negative relation between A. t. cantabriae and M. lusitanicus numbers suggests a competitive displacement between species. The results of the present study have valuable applications for both crop protection and research purposes.

The diet of migrant Red Kites Milvus milvus during a Water Vole Arvicola terrestris outbreak in eastern France and the associated risk of secondary poisoning by the rodenticide bromadiolone

Poisoning by pesticides is considered one of the primary threats to the Red Kite Milvus milvus. We studied the diet of this raptor in an area of eastern France where the rodenticide bromadiolone is widely used to control Water Vole Arvicola terrestris outbreaks. A high degree of specialization for Water Voles was noted, as their remains were identified in all 119 pellets collected in autumn 2008, whereas other small rodent species and insects occurred in 27 and 9% of pellets, respectively. We estimated that Water Voles constituted 94% of the total biomass ingested by Red Kites under these conditions. Based on these data, the risk of secondary poisoning due to feeding on poisoned voles was assessed. Acute exposure on a single day was not considered a risk for Kites, but exposure to poisoned voles over 1 week represented the maximal risk for the Red Kite; the calculated dose of bromadiolone ingested by a Red Kite was 137 times higher than the toxicological benchmark for birds. A field survey in the studied area detected four dead Red Kites and one moribund bird in autumn 2008 but did not confirm that the cause of death was bromadiolone poisoning. We suggest that professional monitoring is needed to assess the impact of rodenticides on Red Kites in areas where voles are controlled.

Inherited phenotypic changes in the population dynamics of water vole (Arvicola terrestris L.) in Northern Baraba

A new method of studying genetic factors in phenotypical variability of rodents is applied for the cycling population of water vole (Arvicola terrestris L.) in Northern Baraba. The components of the maximum additive heritability are found via the correlations “parent-offspring” in vivarium population. The interannual phenotypical variability of natural rodent populations is studied in the space of these components. It is shown that radical genetic restructuring in the population takes place in the phase of low density. The genetic specificity of different cycles of vole population dynamics is confirmed as well. The changes of common animals sizes associated with population dynamics are determined by heterozygosity effects.

Age, season and spatio-temporal factors affecting the prevalence of Echinococcus multilocularis and Taenia taeniaeformis in Arvicola terrestris

BackgroundTaenia taeniaeformis and the related zoonotic cestode Echinococcus multilocularis both infect the water vole Arvicola terrestris. We investigated the effect of age, spatio-temporal and season-related factors on the prevalence of these parasites in their shared intermediate host. The absolute age of the voles was calculated based on their eye lens weights, and we included the mean day temperature and mean precipitation experienced by each individual as independent factors.ResultsOverall prevalences of E. multilocularis and T. taeniaeformis were 15.1% and 23.4%, respectively, in 856 A. terrestris trapped in the canton Zürich, Switzerland. Prevalences were lower in young (≤ 3 months: E. multilocularis 7.6%, T. taeniaeformis 17.9%) than in older animals (>7 months: 32.6% and 34.8%). Only 12 of 129 E. multilocularis-infected voles harboured protoscoleces. Similar proportions of animals with several strobilocerci were found in T. taeniaeformis infected voles of <5 months and ≥5 months of age (12.8% and 11.9%). Multivariate analyses revealed strong spatio-temporal variations in prevalences of E. multilocularis. In one trapping area, prevalences varied on an exceptional high level of 40.6-78.5% during the whole study period. Low temperatures significantly correlated with the infection rate whereas precipitation was of lower importance. Significant spatial variations in prevalences were also identified for Taenia taeniaeformis. Although the trapping period and the meteorological factors temperature and precipitation were included in the best models for explaining the infection risk, their effects were not significant for this parasite.ConclusionsOur results demonstrate that, besides temporal and spatial factors, low temperatures contribute to the risk of infection with E. multilocularis. This suggests that the enhanced survival of E. multilocularis eggs under cold weather conditions determines the level of infection pressure on the intermediate hosts and possibly also the infection risk for human alveolar echincoccosis (AE). Therefore, interventions against the zoonotic cestode E. multilocularis by deworming foxes may be most efficient if conducted just before and during winter.

Niche separation between the weasel Mustela nivalis and the stoat M. erminea in Belarus

We investigated three main niche components (diet composition, habitat use and diel activity rhythms) to examine how the weasel Mustela nivalis and the stoat M. erminea, both specialised predators of small rodents, could permanently coexist in Belarus. Our research was carried out in temperate forests of Belarus, in two study areas with different environmental conditions: 1) continuous dry-land forest interspersed by a variety of swampy biotopes and aquatic ecosystems (Paazerre, northern Belarus) and 2) extended wetland with large forest patches (Palesse, southern Belarus). The habitat use and diel activity rhythms of seven weasels and eight stoats were analysed by radio-tracking over about 300 km2 in Paazerre. Snow-tracking was also applied to study habitat use by the two mustelid species. Diet composition was examined by analysing 365 weasel scats and 606 stoat scats. Our results suggest that while the weasel and stoat occur in close proximity to each other, they use different micro-habitats, are most active during different times of the day, and prey primarily on different small rodent species. Most weasels selected forest and forest edge habitats, where they predominantly preyed on smaller rodent species (bank voles Clethrionomys glareolus and Apodemus mice); stoats selected wetlands, especially open grassy marshes, and preyed more frequently on larger rodents such as water voles Arvicola terrestris and Microtus voles. Weasels were mostly diurnal and adjusted their activity to the seasonally changing length of daylight, whereas stoats were much more active in twilight and during the night.

Effect of mother’s physical condition during pregnancy and lactation on postnatal growth and reproductive success of offspring in water vole Arvicola terrestris

Postnatal growth, life span, and probability of reproduction in the adult state depended on the mother's physical condition during pregnancy and lactation in water vole. The white fat weight in the female abdominal cavity was shown to significantly increase in pregnancy and to decrease in late lactation. As an indicators for nutritional state of females, their body weight difference after parturition (or in late lactation) and expected from the regression equation relating individual body weight at the beginning and the end of each reproductive stage were used (physical condition indexes in pregnancy or lactation). The correlation of the physical condition index in pregnancy with the storage fat weight was 0.67. The metabolic resources of the mother's body proved to favor faster offspring development. The female offspring weight at the age of 3 and 10 weeks as well as adult ones positively correlated with the mother's nutritional state in pregnancy, while the male offspring weight demonstrated a similar correlation at the age of 3 and 6 weeks. Increased negative energy balance during lactation proved to decrease the offspring weight in both sexes after separation from mother and at the age of 6 weeks. High nutritional state of mother in pregnancy favored both the probability of reproduction and life span of female offspring. The reproduction of male offspring did not depend on the mother's physical condition. The life span peaked in male offspring of mothers in a nutritional state below average in pregnancy and above average in lactation. Thus, the physical condition of the mother's body is an important sex-dependent factor of phenotypic variation in the offspring body weight, reproductive competence, and life span.

What limits male range sizes at different population densities? Evidence from three populations of water voles

AbstractIn many mammalian species, females compete with each other for food and space to raise offspring, while males compete with each other for access to females. Few studies have examined the factors which limit male range sizes or the degree of overlap between male ranges. We deduced four possible responses of the range ‐sizes of non‐territorial male small mammals to increasing population density and/or levels of forage abundance. These were: (1) male range sizes might remain the same irrespective of population density; (2) at high population densities males may become territorial, and their ranges small and non‐overlapping; (3) at high forage abundance/population densities, males' ranges may become smaller but remain intra‐sexually overlapping; (4) at high forage abundance, male range sizes may increase. We examined the relationship between population density, range lengths and range overlaps and body weights of both sexes in a comparative study of three populations of water voles Arvicola terrestris. Male range sizes were smaller at higher population densities, but their ranges remained both inter‐ and intra‐sexually overlapping. Heavier males had larger ranges than did lighter males at all sites. These results comply with what would be expected if male range sizes were at least partially restricted by the number of ranges of other individuals with which they overlapped. Although we could not discount the hypothesis that forage abundance may also have had a direct effect on male range sizes, our results implied that male range sizes were at least partially determined by social factors.

Trapping for mink control and water vole survival: Identifying key criteria using a spatially explicit individual based model

Introduced alien species are the second most important threat to global biodiversity after habitat loss. The American mink Mustela vison has been introduced to several countries and is threatening a number of native species worldwide. We developed a spatially explicit and individual based model as a planning tool to identify key criteria for the implementation of trapping campaigns as a way to control open American mink populations. We first predicted the minimum effort required to reduce populations of mink below a certain threshold and the best time of year in which to trap mink to minimise their numbers. We then employed this methodology to predict the best trapping strategy to ensure the long-term survival of the water vole Arvicola terrestris, one of the species most endangered by the spread of the mink in the UK. We also applied the mink and water vole population models to rationalise a set of observed data in an area of 50 × 30 km in the Upper Thames (UK). The model predicted that it is necessary to remove mink for at least 3 months every year and that a mixed strategy of trapping during the mating, late dispersal and winter seasons is best for keeping mink at low densities. Concentrating trapping during the late dispersal and winter seasons is instead best for ensuring the long-term survival of water voles. Targeting immigrating juvenile mink as well as reproductive adults is important. The model also showed that trapping efficiency might be an important factor to consider when choosing periods in which to trap.

Sexual maturation of daughters depends on the mother’s body condition during pregnancy: An example of the water vole Arvicola terrestris L.

The body condition of an animal directly depends on the amount, quality, and assimilation efficiency of available food and on the energy expenditures and may serve as a reliable criterion of both internal and external conditions favorable for the onset of reproduction. The body condition is known to determine the probability of participation in reproduction and its effectiveness [8, 11]. Unlike species that rely on stored body reserves during pregnancy and bringing up the offspring [7], females of many small nonhibernating rodents has to rearrange their energy budget during pregnancy to reach a positive balance. When the amount of energy consumed with food is insufficient to support pregnancy and lactation, the energy deficit is compensated for at the expense of metabolic reserves of the body, primarily, fat [6, 12]. Previous ecological and population studies showed that, in the water vole, the probability of pregnancy failure and the litter size depended on the energy balance. In the years when population density dropped because of reduced food supply and/or stressful situations, a higher concentration of free fatty acids was found in female blood, which testifies to the mobilization of energy substrates from the stores of fat. This was accompanied by a significantly higher frequency of embryo resorption at the postimplantation developmental stage [1]. During the perinatal period, the probability of death of the young also depends on the mother’s body condition. The female body weight after the birth of the offspring is found to exceed their body weight on the day of mating by about 10%. However, in females that display a 100% death rate of offspring, the increase in the body weight during pregnancy was significantly lower (3%) [4]. The effect of the mother’s body condition during gestation on the offspring’s postnatal development remains unstudied so far. The rate of sexual maturation is one of the most plastic parameter that is related to animal growth [5]. Analysis of the contribution of maternal factors to the variation of the rate of the daughters’ sexual maturation in the water vole Arvicola terrestris L. showed that the mother’s body condition during pregnancy had a significant effect on this characteristic. The animals used in our study were kept in a vivarium at the natural photoperiod and received food and water ad libitum. The index of body condition during gestation was defined as the difference between the logarithm of the postpartum body weight and the logarithm of the expected body weight. The logarithm of the expected body weight was calculated from the regression equation of the postpartum body weight on the body weight at mating ( R 2 = 0.81; p < 0.001):

Linking demography and host dispersal to Trichuris arvicolae distribution in a cyclic vole species

Spatial structure in the distribution of pathogen infection can influence both epidemiology and host–parasite coevolutionary processes. It may result from the spatial heterogeneity of intrinsic and extrinsic factors, or from the local population dynamics of hosts and parasites. In this study, we investigated the effects of landscape, host dispersal and demography (population abundance and phase of the fluctuation) on the distribution of a gastro-intestinal nematode Trichuris arvicolae in the fossorial water vole Arvicola terrestris sherman. This rodent exhibits outbreaks occurring regularly in Franche-Comté (France). Thirteen out-of-phase populations were studied in autumn 2003. They exhibited highly different T. arvicolae prevalences. The heterogeneity in prevalences was not explained by population structure, landscape or vole abundance, but by the phase of the vole population fluctuations. Populations at the end of the high density phase showed null prevalence whereas populations in increase or outbreak phases exhibited higher prevalences. Population genetic analyses based on microsatellites revealed significant differentiation between vole populations, and higher dispersal rates of young voles compared with old ones. These younger individuals were also infected more frequently than older voles. This suggested a role of host dispersal in the distribution of T. arvicolae. However, there was a strong discrepancy between the spatial patterns of prevalence and of host genetics or demographic phase. Genetic differentiation and differences in demographic phase exhibited significant spatial autocorrelations whereas prevalence did not. We concluded that the distribution of T. arvicolae is influenced by vole dispersal, although this effect might be overwhelmed by local adaptation processes or environmental conditions.

Variation in the diet composition of a generalist predator, the red fox, in relation to season and density of main prey

Abstract Diet composition of a generalist predator, the red fox ( Vulpes vulpes ) in relation to season (winter or summer) and abundance of multi-annually cyclic voles was studied in western Finland from 1983 to 1995. The proportion of scats (PS; a total of 58 scats) including each food category was calculated for each prey group. Microtus voles (the field vole M. agrestis and the sibling vole M. rossiaemeridionalis ) were the main prey group of foxes (PS = 0.55) and they frequently occurred in the scats both in the winter and summer (PSs 0.50 and 0.62, respectively). There was a positive correlation between the PSs of Microtus voles in the winter diet of foxes and the density indices of these voles in the previous autumn. Other microtine rodents (the bank vole Clethrionomys glareolus , the water vole Arvicola terrestris and the muskrat Ondatra zibethicus ) were consumed more in winter than in summer. The unusually high small mustelid predation by red foxes (PS = approx. 0.10) in our study area gives qualitative support for the hypothesis on the limiting impact of mammalian predators on least weasel and stoat populations. None of the important prey groups was preyed upon more at low than at high densities of main prey ( Microtus voles). This is consistent with the notion that red foxes are generalist predators that tend to opportunistically subsist on many prey groups. Among these prey groups, particularly hares and birds (including grouse), were frequently used as food by foxes.

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.

Decline of invasive alien mink (Mustela vison) is concurrent with recovery of native otters (Lutra lutra)

ABSTRACTInvasive species often cause the decline of native prey or competitors. We highlight a contrasting example of the large‐scale recovery of a native species and the concurrent decline and likely displacement of an established invasive competitor. Invasive American mink Mustela vison became widespread in the British Isles at the same time as native Eurasian otters Lutra lutra were declining as a result of water pollution. In common with other invasive predators, mink cause conservation problems for a range of native prey species, most notably water voles Arvicola terrestris. Recent trends in the distribution of native otters and invasive mink in north‐east England were examined using a novel regression modelling approach to analyse presence/absence data from field surveys, corroborated by contemporary predator culling records. Between 1991 and 2002, the percentage of sites where mink signs were found decreased from 80% to 20%, while otter signs increased from 18% to 80%. Annual indices of mink captures on shooting estates increased between 1980 and 1996, but were followed by a decline thereafter. Indices of the incidence of native otters were significantly related to those indicating the decline or displacement of invasive mink. This large‐scale field study is supportive of localized experimental evidence for the return of dominant, native otters being concurrent with the decline of the invasive alien mink. The recovery of a dominant native species may represent a reversal of the mesopredator release that allowed invasive mink to establish and may eventually serve to mitigate their impact on native prey species.

Stabilizing function of sexual selection in relation to male aggressiveness in rodents

A series of experiments on water voles ( Arvicola terrestris L.) and outbred (Swiss) and inbred (BALB/c and C57BL/6) strains of house mice was performed to estimate the dependence of the attractiveness of male rodents on their aggressiveness. The results showed that females preferred males with intermediate aggressiveness indices, which proved to have higher reproductive capacity. The aggressiveness (aggressiveness index) was measured as the mean ratio of aggressive acts to the total number of social interactions between males placed in the same cage. The males were divided into four groups according to their aggressiveness indices: low-aggressive (with aggressiveness indices varying in different series from 0.00‐0.20, M = 0.13), mediumaggressive (0.45‐0.65, M = 0.55), aggressive (0.65‐0.85, M = 0.75), and high-aggressive (0.85‐1.00, M = 0.93). Olfactory attractiveness was estimated by attractiveness index calculated as the proportion of tests in which the stimulus of the given male (the bedding from its cage) was preferred by a female. The stimulus was considered preferred if a receptive female (at the late proestrus or estrus stage) explored it for a longer time than other stimuli. From 17 to 112 males were studied in individual experimental series. The dependence of the olfactory attractiveness of males on their aggressiveness was not monotonic (figure). Low-aggressive males were the least attractive for females (their mean attractiveness index was M = 0.14), and aggressive males were the most attractive ( M = 0.86). The attractiveness of high-aggressive males ( M = 0.51) was significantly lower than that of aggressive and about the same as that of medium-aggressive ( M = 0.49). Although linear approximation can be applied to the observed dependence of attractiveness on aggressiveness ( r 14 = 0.63, R 2 = 0.40, t = 3.07, p = 0.001), which explains the widespread opinion that it is monotonic, a fourth-degree polynomial approximation considerably better fits the observed dependence ( r 14 = 0.93, R 2 = 0.87, t = 9.81, p < 0.000001).

Physiological consequences of captive conditions in water voles (Arvicola terrestris)

AbstractRe‐introductions of captive‐bred animals are increasingly common in wildlife conservation and it is important that they fulfil their potential. To foster this goal we examined variations in stress levels in a captive‐bred population of water voles Arvicola terrestris in response to housing conditions and radio‐collaring, using weight loss and leukocyte coping capacity (LCC) as measures of relative stress, to investigate the impacts of housing conditions, handling and radio‐collaring on this species. Thirty‐eight water voles (22 males and 16 females) were used in the investigation, 25 housed in outdoor enclosures and 13 in laboratory cages. During the 6‐week study, LCC, body weight and urine refractive index (URI, an indicator of hydration levels) were recorded once a week for each individual in weeks 1, 2, 4 and 6. After the first sample, radio‐collars were attached to 20 individuals (10 males and 10 females) taken from both housing types. Throughout the experiment laboratory‐cage housed voles weighed less, had lower LCC scores – indicating a reduced ability to combat infection – and had higher URIs than outdoor‐enclosure voles. This suggests that the laboratory‐cage voles were more stressed and dehydrated than the outdoor‐enclosure voles. Weights and LCC scores of both housing groups decreased as the study progressed, suggesting that elements of the study, such as repeated handling, may have caused stress to both groups. Evidence suggested a short‐term effect of radio‐collaring on immuno‐competence. We conclude that captive housing conditions, repeated manipulation and radio‐collaring had demonstrable physiological effects on the water voles studied. We recommend that the effects of husbandry and tagging practices upon captive‐bred mammals be closely studied as part of the quest to improve the success of the re‐introductions to which they contribute.

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.