Water Vole Arvicola Terrestris Research Articles

Isolation and characterization of a MHC class II DRB locus in the European water vole (Arvicola terrestris)

In so-called model species, such as human and mouse, genes of the major histocompatibility complex (MHC) are characterized by extremely high levels of polymorphism, and it is considered that such diversity is maintained by balancing selection. ;There is now a recognized need to expand studies into nonmodel species to examine whether high MHC diversity is mirrored in natural populations, and to determine the ecological, ethological, and evolutionary processes that underpin balancing selection. To address such issues, a necessary prerequisite is the ability to characterize diversity at a single, expressed, polymorphic MHC locus on which selection may be acting. Here, we provide the first description of allelic diversity at exon 2 of an MHC class II DRB locus in the European water vole (Arvicola terrestris), characterize variation across four natural populations, and test whether the patterns of variation are consistent with the effects of balancing selection. Using single-strand conformation polymorphism analysis and subsequent DNA sequencing of gel excisions, five DRB alleles were resolved, each with a unique amino acid sequence, among 100 individuals from four geographically distinct populations. Reverse transcription polymerase chain reaction confirmed that the alleles were products from an expressed locus. Intra-allelic amino acid differences were high (10.5-33.3%), and the nonsynonymous substitution rate exceeded the synonymous substitution rate for the functional peptide-binding region (d (N):d (S)=3.91 and P<0.005). Phylogenetic comparison of resolved alleles with closely related homologues indicated that each allele represented a unique lineage preserved across speciation events. These results indicate that balancing selection has maintained diversity of DRB allelic lineages and amino acid function over evolutionary time scales, but may be less effective at preserving alleles in contemporary populations where stochastic microevolutionary processes may dominate.

Widespread gene flow and high genetic variability in populations of water volesArvicola terrestrisin patchy habitats

Theory predicts that the impact of gene flow on the genetic structure of populations in patchy habitats depends on its scale and the demographic attributes of demes (e.g. local colony sizes and timing of reproduction), but empirical evidence is scarce. We inferred the impact of gene flow on genetic structure among populations of water voles Arvicola terrestris that differed in average colony sizes, population turnover and degree of patchiness. Colonies typically consisted of few reproducing adults and several juveniles. Twelve polymorphic microsatellite DNA loci were examined. Levels of individual genetic variability in all areas were high (H(O) = 0.69-0.78). Assignments of juveniles to parents revealed frequent dispersal over long distances. The populations showed negative F(IS) values among juveniles, F(IS) values around zero among adults, high F(ST) values among colonies for juveniles, and moderate, often insignificant, F(ST) values for parents. We inferred that excess heterozygosity within colonies reflected the few individuals dispersing from a large area to form discrete breeding colonies. Thus pre-breeding dispersal followed by rapid reproduction results in a seasonal increase in differentiation due to local family groups. Genetic variation was as high in low-density populations in patchy habitats as in populations in continuous habitats used for comparison. In contrast to most theoretical predictions, we found that populations living in patchy habitats can maintain high levels of genetic variability when only a few adults contribute to breeding in each colony, when the variance of reproductive success among colonies is likely to be low, and when dispersal between colonies exceeds nearest-neighbour distances.

How moles contribute to colonization success of water voles in grassland: implications for control

Summary Outbreaks of the water vole Arvicola terrestris cause severe damage in grasslands of upland regions of Europe. The sheer speed of this phenomenon is a challenge to effective pest control measures. While there has been some research into factors that promote outbreaks, especially landscape composition, little is yet known of the biological mechanisms underlying the speed of colonization of grasslands during the population growth stage. Like A. terrestris, the mole Talpa europaea digs vast tunnel networks that may be used by A. terrestris. The availability of extensive networks of this sort might greatly boost the colonization potential of A. terrestris and so explain the speed of onset of its outbreaks. Areas occupied by networks of A. terrestris and T. europaea tunnels, and their respective locations, were evaluated and mapped with a global positioning system (GPS) during low‐density, growth and the first weeks of abundance phases of cyclic fluctuations of A. terrestris. During the growth phase and the first weeks of the abundance phase nearly 80% of new A. terrestris colonies were found in T. europaea tunnel networks, although these occupied just 20% of the area under study. The regulating influence of wooded areas on the risk of outbreaks, which can be identified at larger spatial scales (region, sector), was imperceptible at local scales, probably because of the influence and relative extent of T. europaea tunnel networks. There was a threshold level of occupancy of grassland by T. europaea, as indexed by surface indices, below which A. terrestris populations were regulated naturally and over long periods. Synthesis and applications. These findings have implications for controlling outbreaks of A. terrestris. Temporally, chemical pest control of A. terrestris can be reduced by taking action during the A. terrestris low‐density phases, preferably in the autumn. Spatially, control operations should be targeted at T. europaea and early A. terrestris networks. Mechanical destruction of tunnels (e.g. ploughing) and trapping should be considered as an alternative to chemical pest control.

An assessment of the local impact of native predators on an established population of British water voles ( Arvicola terrestris )

There is a considerable amount of literature on the diet and effect of feral American mink Mustela vison on the distribution and abundance of water voles Arvicola terrestris in Britain. Few recent studies, however, have attempted to examine the occurrence of water voles in the diets of native predators. Fox Vulpes vulpes scat and grey heron Ardea cinerea pellets were collected during winter 2003–2004 at a location known to contain a large number of water voles. These scats and pellets were subsequently analysed to determine the frequency of water vole occurrence in the diet of these opportunistic predators. Water vole remains were found in 30% of fox scats analysed and accounted for 13% of the total weight of scats. A total of 18% of heron pellets contained the fur of water voles in addition to the fur of four other rodent species. The potential role of native predators in the loss and fragmentation of site-specific populations of water voles in Britain is further discussed.

Cluster of Capillaria hepatica infections in non-commensal rodents from the canton of Geneva, Switzerland

We trapped 664 rodents belonging to five non-commensal species in the canton of Geneva, Switzerland, and found a significant cluster of Capillaria hepatica infections in three species in rural and urbanized areas of the northern part of the canton. C. hepatica infections were discovered in the yellow-necked mouse Apodemus flavicollis (n=99) with an overall prevalence (OP) of 7.0% and a clustered prevalence (CP) of 20%, in the bank vole Clethrionomys glareolus (n=58, OP 5.2%; CP 19%), and in the water vole Arvicola terrestris scherman (n=466; OP 0.2%; CP 4%). The estimated numbers of C. hepatica eggs isolated from infected livers ranged from 1,914 to 938,000 per animal.

Indirect negative impacts of radio‐collaring: sex ratio variation in water voles

SummaryRadio‐tracking is used ubiquitously in studies of wild vertebrates, a fundamental assumption being that tagged animals do not significantly differ, behaviourally or otherwise, from untagged animals.We studied two populations of water volesArvicola terrestris: one population was live‐trapped from April to September for 2 years (2000, 2001) and then concurrently radio‐tracked and trapped in a third year (2002). The second population was trapped only during 2002.During 2002, a substantial decline in female numbers in the radio‐collared population was recorded, apparently resulting from a male skew in the sex ratios of offspring born to this population. The mean numbers of males and females born duringtrappingonly were 25·7 (SD 2·1) and 29·0 (SD 7·0), respectively. Recruits to theradio‐trackedpopulation were skewed heavily in favour of males (43 : 13).Both hypotheses commonly invoked to explain mammalian sex‐ratio manipulation refer to the condition of mothers. The altered sex ratio resulted from a 48% decrease in numbers of females born, a decrease similar to the proportion (0·49) of the female population that was collared. No similar decline in male births occurred. This suggests that radio‐collaring of females caused male‐skewed sex ratios.Synthesis and applications. We conclude that the observed decline in female numbers resulted from male‐skewed recruitment sex ratios due to the attachment of radio‐collars to female water voles. These results question the assumption that the use of radio‐collars does not fundamentally affect the biology of collared water voles.

Natural infection of the water vole Arvicola terrestris with Toxoplasma gondii, on the Jura plateau, eastern France.

102 A. terrestris (all juveniles) were caught between July 1992 and July 1993 from an area near the French village of Le Souillot, dissected and examined for coccidian tissue cysts. Five of the animals were found to have tissue cysts in their brains. Although histological sections of the 5 infected brains all revealed round cysts, each measuring <150 micro m in diameter, 2 of the brains had cysts that were morphologically similar to those of T. gondii, with crescent-shaped zoites. The cysts in the other three brains had spherical zoites, each with a central nucleus. Immunoperoxidase labelling confirmed the two brains had T. gondii cysts (2%). The cysts in the other 3 infected brains, which showed no reaction with the anti-Toxoplasma or anti-Neospora sera, were assumed to be young cysts of Frenkelia.

Demographic and genetic structure of fossorial water voles (Arvicola terrestris) on Scottish islands

AbstractThe distribution of fossorial water voles Arvicola terrestris on 15 small islands in the Sound of Jura, Argyll, Scotland, was established and populations were characterized in terms of size, structure and genetic composition (12 microsatellites). The results are compared with similar data from four metapopulations of riparian water voles in mainland Scotland. Water voles occurred on six islands, one of which was occupied in 1994, but not on two islands occupied during the 1960s. Probability of occupancy was significantly associated with proximity to the nearest occupied island. Unlike voles on the mainland, which occupy fragmented patches of exclusively riparian habitat, voles on islands were fossorial and occupied large areas of continuous habitat. Spring population sizes were c. 10 times higher on the islands than colonies of mainland metapopulations. Individuals from three islands were genotyped and these populations had 50% lower levels of microsatellite polymorphism than the mainland metapopulations. Rates of inferred contemporary dispersal among islands separated by 1 km or more of sea were very low, according to large differences among islands in genetic composition, proportions of coat colour types and incidence of skin infection. None the less, the long‐term persistence of the island populations is likely to depend on such dispersal. Comparisons between island populations and mainland metapopulations indicate that in both fragmented systems the level of dispersal is the primary factor influencing genetic structure. The low genetic variability in the island populations may reflect either past historical events (founder effect and genetic drift) or present ecology (lack of immigration in closed and temporally fluctuating populations).

The impact of American mink Mustela vison and European mink Mustela lutreola on water voles Arvicola terrestris in Belarus

In the U.K. the impact of introduced American mink Mustela vison, on water voles Arvicola terrestris, may be exacerbated by habitat loss and fragmentation. Pristine wetlands in Belarus, which American mink invaded in the early 1990s, provide a three‐pronged opportunity to test this hypothesis. First, we examine the evidence that, even in the unmanaged wetlands of our Belarussian study site, American mink have reduced water vole populations. Second, we ask whether habitat size, type and isolation mitigate the impact of American mink predation. Thirdly, we explore whether water voles are at greater risk of predation from American than European mink because of their patterns of habitat use. Following the invasion of American mink, water voles were most abundant in small, still‐water sites, far from river banks, while American mink were most active in large, running‐water sites. Small mammal remains were found in a higher percentage of American than European mink scats, and of these, more were water vole in American mink scats. The occurrence of water voles in scats of both mink species declined after the American mink invaded and established. Our results provide at least circumstantial evidence that American mink limit water vole populations even in unmanaged wetland eco‐systems, and that they have a greater impact than their European congener at least partly because they make greater use of isolated marshes. Although by no means providing complete protection, the configuration and dispersion of available habitat mitigated the impact of American mink on water voles. This raises the possibility that habitat restoration, especially through the establishment of isolated enclaves, could help reduce the effect of American mink in the U.K. These observations are of broader interest in the context of assessing the effect of multiple pressures on vulnerable species.

Population changes of different predators during a water vole cycle in a central European mountainous habitat

Population changes in long‐eared owls Asio otus, polecats Mustela putorius, red foxes Vulpes vulpes, stone martens Martes foina and badgers Meles meles were monitored during a water vole Arvicola terrestris scherman cycle in western Switzerland. Long‐eared owls confirmed their status of highly mobile specialist predators in responding strongly and without time lag to water vole population changes. Even though polecats are considered generalists, they exhibited also a strong response to water vole fluctuations. Their numbers tracked water vole densities with a 1‐yr time lag. Marked population changes were also recorded in red foxes and stone martens, but these changes were not related to water vole densities. Lastly, badgers did not show any significant population changes during the water vole cycle. We discuss the possible reasons for these differences and conclude that multi‐factorial approach is clearly required to understand population processes in predator‐prey systems.

The use of willingness‐to‐pay approaches in mammal conservation

ABSTRACTWith limited monetary resources available for nature conservation, policy‐makers need to be able to prioritize conservation objectives. This has traditionally been done using qualitative ecological criteria. However, since declines in species and habitats are largely the result of socio‐economic and political forces, human preferences and values should also be taken into account. An environmental economics technique, contingent valuation, provides one way of doing this by quantifying public willingness‐to‐pay towards specific conservation objectives.In this paper, the use of this approach for quantifying public preferences towards the UK Biodiversity Action Plans for four different British mammal species is considered. The species included are the Red Squirrel Sciurus vulgaris, the Brown Hare Lepus europaeus, the Otter Lutra lutra and the Water Vole Arvicola terrestris. Willingness‐to‐pay for conservation was increased by the inclusion of the Otter among the species, membership of an environmental organization and awareness of the general and species‐specific threats facing British mammals. It was reduced by the presence of the Brown Hare among the species being considered.These findings for British mammals are compared with other willingness‐to‐pay studies for mammal conservation worldwide. Willingness‐to‐pay tends to be greater for marine mammals than terrestrial ones, and recreational users of species (tourists or hunters) are generally more willing than residents to pay towards species conservation. The choice of technique for eliciting willingness‐to‐pay from respondents is also shown to be highly significant.Willingness‐to‐pay values for British mammals derived from contingent valuation are sensitive to the species included rather than merely symbolic. This indicates that, with care, such measures can be used as a reliable means of quantifying public preferences for conservation, and therefore contributing to the decision‐making process. However, irrespective of the internal consistency of contingent valuation, the validity of the approach, especially for use in nature conservation, is disputed. Willingness‐to‐pay is likely to reflect many interrelated factors such as ethical and moral values, knowledge and tradition, and monetary values may not be an adequate representation of these broader considerations. Willingness‐to‐pay approaches should therefore be used in addition to, rather than in place of, expert judgements and more deliberative approaches towards policy decision‐making for conservation.

Landscape composition and vole outbreaks: evidence from an eight year study of Arvicola terrestris

This study investigates the relationships between landscape composition and the population dynamics of the fossorial water vole Arvicola terrestris. Land use patterns were studied based on agricultural and forestry data from the French Ministry of Agriculture collected in 1955 and 1988. In the Massif Central, France, water vole populations were monitored from 1985 to 1993 by using index methods. Outbreaks of water vole populations occurred in many dispersed epicentres and spread suddenly and widely over &gt; 7500 km2. At a regional scale, the fluctuation lasts six years on average with an outbreak period lasting from two to three years. Density variation patterns are positively correlated with the proportion of permanent grassland to agricultural land. A high risk of outbreak is linked to a high proportion of permanent grassland (over 90%), whereas a low risk of outbreak is linked to a proportion of &lt; 80%, Conversely, density variation patterns are negatively correlated with the proportion of temporary grassland to agricultural land and with the proportion of forest to total land in the western (major) part of the study area. Temporary grassland thus appears to be a marginal habitat for water voles and extensive forests could act as a brake on outbreaks. The increase in the area of permanent grassland from 1955 to 1988 was apparently the major cause of chronic high densities of water voles. Therefore, land use and landscape management could be one way to control water vole outbreaks.

Modelling the effects of mink and habitat fragmentation on the water vole

Summary1. The decline of the water voleArvicola terrestrisin the UK has been attributed to the spread of the introduced American minkMustela vison. Understanding the causes and dynamics of this decline is vital to water vole conservation. We investigated the dynamics of water voles in relation to habitat fragmentation and mink predation using an individual‐based spatially explicit model of population dynamics on the River Windrush, Oxfordshire, UK.2. A sensitivity analysis was undertaken using values for life‐history parameters drawn from known ranges using Latin hypercube sampling. Partial correlation coefficients were used to estimate how the predicted size of water vole population and extinction were determined by the life‐history parameters. The model was then validated by comparing model predictions with observed distributions of water voles.3. The effects of mink predation and habitat fragmentation on the future viability of water vole populations on the River Windrush were analysed after artificially manipulating habitat fragmentation on the river and running the model in the presence and absence of mink predation.4. The match between predicted and observed distributions was significantly related to home range requirement and high reproductive success. At low fragmentation, home range requirement was the most important influence on the number of populations. Reproductive output, and adult and juvenile mortality, became increasingly important with increased fragmentation. At high levels of fragmentation demographic stochasticity had a large influence on population size.5. We deduce that the importance of demography in determining population persistence will depend on the level of fragmentation. Additionally, life‐history parameters that are crucial to the viability of water vole populations can only be identified in the context of the landscape in which populations are found.6. The extinction of water vole on the River Windrush became more likely as habitat fragmentation and mink predation increased. Mink predation effectively doubled the probability of extinction over that arising from fragmentation alone.7. These simulations indicate that extant populations on the Windrush are now so fragmented that populations may not be viable even in the absence of mink predation. We assessed the extent of habitat restoration necessary to ensure population persistence on the River Windrush and considered developments of the model for use in water vole conservation.

Landscape effects on the population dynamics of the fossorial form of the water vole (Arvicola terrestris sherman)

The dynamics of microtine rodents show large variations among species and even among populations of a single species. Several studies have shown that landscape structure and predation play a role in these variations. We studied the influence of landscape structure on the spatial distribution and the population dynamics of the fossorial form of the water vole (Arvicola terrestris sherman). The sampling was based on a preliminary five-year survey of a rodent cycle on a regional scale, as well as a method of abundance estimation using surface indices. This survey led to distinguishing epicentres where outbreaks started, and diffusion sections where outbreaks occurred later. Results showed differences in dynamics of spatial distribution of the vole colonies between these two types of sections. This distribution pattern is related to landscape composition and structure. Epicentres are characterized by a higher ratio of open landscape, a lower ratio of forest, and less fragmentation when compared to the diffusion sections. Therefore landscape analysis has the potential of providing a valuable framework for the designing of programs for the early control of A. terrestris populations.

Breeding success of the red fox Vulpes vulpes in relation to fluctuating prey in central Europe

The influence of water vole Arvicola terrestris scherman fluctuations on red fox Vulpes vulpes reproduction was investigated in a central European mountainous habitat. We also examined the relationship between annual variations in the mean body weight of the cubs and trophic changes. Water vole abundance was estimated by seasonal trappings, and fox families and cubs were counted every spring. The number of fox families differed little between years, and the differences were not related to water vole abundance. Mean litter size also varied from year to year, but independently of water vole densities. No relation was found between the weight of the cubs and water vole supply. The lack of any significant annual variations in fox breeding success means that despite the low availability of wild alternative prey, foxes found suitable trophic conditions in the absence of water voles. Moreover, as suggested by the increase in the consumption of food scraps by foxes during vole lows, man has certainly been instrumental in preventing a decrease in fox breeding success at the low stage of the water vole cycle.

Estimating numbers of the water vole Arvicola terrestris: a correction to the published method

In Britain, the water vole (Arvicola terrestris) has declined in numbers and distribution (Jefferies, Morris & Mulleneux, 1989; Strachan & Jefferies, 1993). This species now enjoys a higher profile than hitherto and many local surveys have been initiated, following published methods. To monitor the status of the population or the effectiveness of habitat restoration projects, a method for estimating numbers of water voles is often needed, preferably based on latrines (a characteristic field sign of this species). Unfortunately, the published literature includes two potentially misleading components. In view of the significance of population size in a declining species, and the heightened interest in this animal, we felt it would be helpful to publish clarification and corrections in the hope of forestalling erroneous reports and conclusions in future investigations.

Economic values of threatened mammals in Britain: A case study of the otter Lutra lutra and the water vole Arvicola terrestris

We investigated the relative economic values of the otter Lutra lutra and the water vole Arvicola terrestris, two species that occupy similar habitats and face common threats of habitat change, habitat fragmentation and pollution. Willingness to pay for conservation was estimated using the contingent valuation method. Data were collected by a telephone survey using a referendum based on willingness to pay a specified amount as a single addition to tax. The most influential variables in determining respondents' willingness to pay were their age, the specified tax amount, whether they were aware of the threats to that specific species, whether they were a member of a conservation organisation and whether they walked frequently in the countryside. Mean willingness to pay values obtained were £11·91 for the otter, £7·44 for the water vole, and £10·92 for both species together. Aggregated over the survey population of North Yorkshire, these results equate to £6·4 million, £4·0 million and £5·8 million, respectively. These figures are well in excess of the calculated present values for the UK action plans for the otter and the water vole (£0·8 million and £1·0 million, respectively). The results demonstrate strong public support for mammal conservation, in particular for high profile ‘flagship’ species, and suggest that public profile may be as important as rarity or the degree of threat in determining a species' relative economic value.

Deprivation of Food during Pregnancy and Reproduction in the Water Vole (Arvicola terrestris)

The effect of food deprivation (for 16 h on day 15 and day 18 of gestation) on reproduction in water voles ( Arvicola terrestris ) and their offspring was examined. In food-deprived mothers, fecundity was diminished and sex ratio of young was skewed toward males. Maternal food deprivation in late pregnancy had no effect on the reproductive performance of young males, but it increased reproductive potency of young females. A prolonged positive effect of food restriction on reproduction of female offspring may be important in restoring the size of the population in the next generation.

Introduced carnivores in Europe with special reference to central and northern Europe

The American mink Mustela vison, raccoon dog Nyctereutes procyonoides and raccoon Procyon lotor are introduced carnivores in Europe. The first American minks were brought to European fur farms in the late 1920s, when also the first raccoons were released, and raccoon dogs were released in the 1930s. The numbers of American minks and raccoon dogs increased rapidly, and today they are widely distributed in Europe. The range of the raccoon is restricted to Germany and adjacent countries and Belorussia. Minks are generalist predators whereas raccoon dogs and raccoons are omnivorous. Thus, e.g. birds and their eggs form part of the diet of these species. Minks are known to have caused damage to colonial ground‐nesting sea‐birds. Some bird populations have, however, adapted to the presence of mink in a few years. The American mink may also have played a role in the decline of the European desman Galemys pyrenaicus in Spain and the water voleArvicola terrestris in England. It may also compete with the otter Lutra lutra, European mink Mustela lutreola and polecat M. putorius. Male American minks can mate with female European minks whose embryos may die. Hence, the American mink may be one of the reasons behind the decline of the European mink. Raccoon dogs can be locally harmful to waterfowl colonies and frogs, but their overall significance to the native fauna seems to be slight. Little is known about the predation or competition of the raccoon with the native fauna in Europe. The raccoon dog and raccoon can, however, be vectors of rabies; e.g. in Finland, the raccoon dog was the main vector of rabies during the epizootic in 1988–1989. The raccoon dog can also be a vector of e.g. sarcoptic mange and trichinosis.

American mink Mustela vison in the upper Thames catchment: Relationship with selected prey species and den availability

American mink Mustela vison and three prey types of economic and conservation importance were censused along four rivers in the Upper Thames catchment area. There were no significant correlations between any measures of mink abundance and any measures of fish or moorhen Gallinula chloropus abundance, suggesting that mink were neither limiting nor limited by these prey items. Water voles Arvicola terrestris, however, were negatively correlated with mink, being absent at four sites where mink were most numerous. Sites at which mink were most numerous had a high availability of potential den sites and low emergent vegetation cover, but there were no correlations between water voles and the availability of their preferred habitat.