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Vole Populations (vole + population)
Selected AbstractsSpatial synchrony in field vole Microtus agrestis abundance in a coniferous forest in northern England: the role of vole-eating raptorsJOURNAL OF APPLIED ECOLOGY, Issue 2000S.J. Petty 1.,The regional synchrony hypothesis (RSH) states that synchrony in microtine abundance over large geographical areas is caused by nomadic avian predators that specialize on small mammals for food. This has proved a difficult hypothesis to test because experiments at an appropriate scale are almost impossible. 2.,We used the decline of the most abundant, nomadic vole-eating raptors in an extensive conifer forest in northern England (Kielder Forest) as a natural experiment to evaluate their influence on synchronizing voles at different spatial scales. Field vole populations fluctuated on a 3,4-year cycle of abundance, similar to the periodicity in central Fennoscandia. 3.,Over a 23-year period, the combined numbers and density of kestrels and short-eared owls significantly declined. If these raptors were responsible for synchronizing vole abundance, the decline should have been associated with a decrease in synchrony. We could find no change in synchrony during the period of the greatest decline in kestrel and short-eared owl numbers (1980,97). 4.,In Kielder, vole abundance has been shown to change in a wave-like manner, with synchrony in the direction of the wave being 5,10-fold smaller than that reported in Fennoscandia. Tawny owls are sedentary and the most abundant vole-eating raptor in our study area, and might have an equalizing influence on vole abundance over smaller areas if they foraged in a density-dependent manner and responded functionally to increasing vole density. If this was the case, spatial variability in vole density should have been less in occupied than unoccupied owl territories, especially in years of low vole density when owls could take a larger proportion of the standing crop of voles. Even though tawny owls caught a significant proportion of the vole population, we could find no difference in variation in vole density between owl territories that were unoccupied, occupied with no breeding attempt, or occupied with a successful breeding attempt. 5.,We conclude that the small-scale synchrony in field vole abundance is unlikely to be caused by avian predators. Instead, it is more likely to be related to the pattern of clear-cutting that has developed in Kielder, which restricts vole dispersal. If this assumption is correct, we would predict more widespread synchrony in vole abundance in first-generation forests when extensive areas are planted over short periods of time, and this is supported by anecdotal evidence. These conclusions indicate that foresters may be able to manipulate the spatial dynamics of voles and vole predators by varying patch sizes within forests. [source] A large panel of novel microsatellite markers for the bank vole (Myodes glareolus)MOLECULAR ECOLOGY RESOURCES, Issue 5 2008K. RIKALAINEN Abstract We describe a set of 66 highly polymorphic microsatellite loci isolated from the bank vole, Myodes (Clethrionomys) glareolus. These microsatellites were characterized for a long-term study on periodically fluctuating density of the bank vole population in Central Finland. We detected six to 38 alleles per locus in the population sampled at two different density phases, and the levels of observed and expected heterozygosities varied between 0.17 and 1.00, and between 0.72 and 0.95, respectively. This microsatellite panel serves as an informative tool for population and molecular genetic studies. [source] Numerical and dietary responses of a predator community in a temperate zone of EuropeECOGRAPHY, Issue 2 2009Gilles Dupuy The generalist predation hypothesis predicts that the functional responses of generalist predator species should be quicker than those of specialist predators and have a regulating effect on vole populations. New interpretations of their role in temperate ecosystems have, however, reactivated a debate suggesting generalist predators may have a destabilizing effect under certain conditions (e.g. landscape homogeneity, low prey diversity, temporary dominance of 1 prey species associated with a high degree of dietary specialization). We studied a rich predator community dominated by generalist carnivores (Martes spp., Vulpes vulpes, Felis catus) over a 6 yr period in farmland and woodland in France. The most frequent prey were small rodents (mostly Microtus arvalis, a grassland species, and Apodemus spp., a woodland species). Alternative prey were diverse and dominated by lagomorphs (Oryctolagus cuniculus, Lepus europeus). We detected a numerical response among specialist carnivores but not among generalist predators. The dietary responses of generalist predators were fairly complex and most often dependent on variation in density of at least 1 prey species. These results support the generalist predation hypothesis. We document a switch to alternative prey, an increase of diet diversity, and a decrease of diet overlap between small and medium-sized generalists during the low density phase of M. arvalis. In this ecosystem, the high density phases of small mammal species are synchronous and cause a temporary specializing of several generalist predator species. This rapid functional response may indicate the predominant role of generalists in low amplitude population cycles of voles observed in some temperate areas. [source] Landscape composition and vole outbreaks: evidence from an eight year study of Arvicola terrestrisECOGRAPHY, Issue 6 2000E. Fichet-Calvet 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 > 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 < 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. [source] Hormetic effects of gamma radiation on the stress axis of natural populations of meadow voles (Microtus pennsylvanicus)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2005Rudy Boonstra Abstract We tested the hypothesis that low doses of gamma radiation have beneficial, hormetic effects on the stress axis (the hypothalamic-pituitary-adrenocortical axis) of free-ranging meadow vole populations (Microtus pennsylvanicus). Voles were exposed to chronic gamma radiation from a 137Cs field irradiator. In isolated populations, voles received one of three treatments over a four-year period: Controls (0.19,0.42 ,Gy/h , levels that were 2,5X above background levels [0.1 ,Gy/h] and live-trapped in all years , 1982,1985), low doses (22.6 ,Gy/h , 50,200X background, live-trapped from November 1982,April 1985), or high doses (3,840 ,Gy/h , 40,000X background, live-trapped from November 1983,April 1985). Voles exposed to a low dose had levels of free and total corticosterone that were significantly higher than those in the control or high-dose groups. Differences in response to radiation between the sexes were apparent for maximum corticosterone-binding capacity, with females exposed to low doses having higher binding capacity than control or high-dose females, whereas males exposed to low doses had lower binding capacity than control or high-dose males. Low-dose voles had higher counts of neutrophils than either the controls or high-dose voles; hematocrit was greater in the controls than in irradiated voles. These results indicate that voles display a hormetic response to radiation, wherein low doses of an otherwise harmful agent produce a beneficial effect. The stimulation of the stress axis resulting in the increased secretion of glucocorticoids, which may protect against the excessive actions of the immune and inflammatory responses, may be a key mechanism producing this effect. [source] Spatial synchrony in field vole Microtus agrestis abundance in a coniferous forest in northern England: the role of vole-eating raptorsJOURNAL OF APPLIED ECOLOGY, Issue 2000S.J. Petty 1.,The regional synchrony hypothesis (RSH) states that synchrony in microtine abundance over large geographical areas is caused by nomadic avian predators that specialize on small mammals for food. This has proved a difficult hypothesis to test because experiments at an appropriate scale are almost impossible. 2.,We used the decline of the most abundant, nomadic vole-eating raptors in an extensive conifer forest in northern England (Kielder Forest) as a natural experiment to evaluate their influence on synchronizing voles at different spatial scales. Field vole populations fluctuated on a 3,4-year cycle of abundance, similar to the periodicity in central Fennoscandia. 3.,Over a 23-year period, the combined numbers and density of kestrels and short-eared owls significantly declined. If these raptors were responsible for synchronizing vole abundance, the decline should have been associated with a decrease in synchrony. We could find no change in synchrony during the period of the greatest decline in kestrel and short-eared owl numbers (1980,97). 4.,In Kielder, vole abundance has been shown to change in a wave-like manner, with synchrony in the direction of the wave being 5,10-fold smaller than that reported in Fennoscandia. Tawny owls are sedentary and the most abundant vole-eating raptor in our study area, and might have an equalizing influence on vole abundance over smaller areas if they foraged in a density-dependent manner and responded functionally to increasing vole density. If this was the case, spatial variability in vole density should have been less in occupied than unoccupied owl territories, especially in years of low vole density when owls could take a larger proportion of the standing crop of voles. Even though tawny owls caught a significant proportion of the vole population, we could find no difference in variation in vole density between owl territories that were unoccupied, occupied with no breeding attempt, or occupied with a successful breeding attempt. 5.,We conclude that the small-scale synchrony in field vole abundance is unlikely to be caused by avian predators. Instead, it is more likely to be related to the pattern of clear-cutting that has developed in Kielder, which restricts vole dispersal. If this assumption is correct, we would predict more widespread synchrony in vole abundance in first-generation forests when extensive areas are planted over short periods of time, and this is supported by anecdotal evidence. These conclusions indicate that foresters may be able to manipulate the spatial dynamics of voles and vole predators by varying patch sizes within forests. [source] Glacial survival or late glacial colonization?JOURNAL OF BIOGEOGRAPHY, Issue 12 2006Phylogeography of the root vole (Microtus oeconomus) in north-west Norway Abstract Aim, It has been proposed that the root vole subspecies, Microtus oeconomus finmarchicus, survived the last glacial period on islands on the north-west coast of Norway. The Norwegian island of Andøya may have constituted the only site with permanent ice-free conditions. Geological surveys and fossil finds from Andøya demonstrate that survival throughout the last glacial maximum was probably possible for some plants and animals. In this study we aim to infer the recent evolutionary history of Norwegian root vole populations and to evaluate the glacial survival hypothesis. Methods, DNA sequence variation in the mitochondrial cytochrome b gene was studied in 46 root voles from 19 localities. Location, Northern Fennoscandia and north-west Russia with a focus on islands on the north-west coast of Norway. Results The phylogeographical analyses revealed two North European phylogroups labelled ,Andøya' and ,Fennoscandia'. The Andøya phylogroup contained root voles from the Norwegian islands of Andøya, Ringvassøya and Reinøya and two localities in north-west Russia. The Fennoscandian phylogroup encompassed root voles from the three Norwegian islands of Kvaløya, Håkøya and Arnøya and the remaining specimens from Norway, northern Sweden and Finland. Nucleotide diversity within the Andøya and Fennoscandian phylogroups was similar, ranging from 0.5% to 0.7%. Main conclusions Both our genetic data and previously published morphological data are consistent with in situ glacial survival of root voles on Andøya during the last glacial maximum. However, the level of genetic diversity observed in the extant island populations, the past periods of severe climatic conditions on Andøya and the ecology of the root vole are somewhat difficult to reconcile with this model. A biogeographical scenario involving late glacial recolonization along the northern coasts of Russia and Norway therefore represents a viable alternative. Our results demonstrate that complex recolonization and extinction histories can generate intricate phylogeographical patterns and relatively high levels of genetic variation in northern populations. [source] Species-specific limitation of vole population growth by least weasel predation: facilitation of coexistence?OIKOS, Issue 1 2008Elina Koivisto Interspecific competition is usually understood as different species competing directly with each other for limited resources. However, predators can alter such competitive interactions substantially. Predation can promote the coexistence of species in a situation where it would otherwise be impossible, for example if a tradeoff between the competitive abilities and predation resistance of the prey species exists. The field vole Microtus agrestis and the sibling vole M. rossiaemeridionalis are sympatric grassland species, which compete for the same resources. At the population level sibling voles are suggested to be superior competitors to field voles, yet more vulnerable to predation. We tested the effects of predation on the two species in 0.5 ha outdoor enclosures by exposing vole populations to radio-collared freely-hunting least weasels Mustela nivalis nivalis for three weeks. Lethal and non-lethal impacts of predation limited population densities of both species during and after the experimental period, but the effect was more pronounced in sibling voles in which population densities decreased markedly during the treatment period and even after that. Field vole population densities remained stable under weasel predation, while densities increased in controls. Survival in both species was lower in treatment populations compared to controls, but the effect tended to be more pronounced in sibling voles and in females of both species. The average mass of adults in both species declined in the treatment populations. These results suggest that predation by least weasels can limit vole populations locally, even during favourable summer conditions, and have extended negative effects on the dynamics of vole populations. In addition, predation alleviated interspecific competition between the vole species and is, therefore, a potential factor enabling the coexistence of them. [source] Phase dependence in winter physiological condition of cyclic volesOIKOS, Issue 4 2007Otso Huitu Lack of food resources has been suggested as a factor which limits the growth of cyclic vole populations. During peak phases of the cycle, vole population growth typically ceases during late autumn or early winter, and is followed by a decrease in density over the winter. To investigate whether this decrease is due to increased mortality induced by a depletion of food resources, we studied overwinter food consumption and physiological condition of field voles (Microtus agrestis) in western Finland in both an increase and a decrease phase of a three-year population cycle. The growth rate of vole populations was negatively related both to prevailing vole densities and to densities six months earlier. The condition index of voles, as well as their blood levels of haematocrit, proteins, free fatty acids and immunoglobulin G, were positively related to population growth rate when populations were declining. When populations were increasing, these parameters tended to be negatively related to population growth rate. The overall physiological condition of voles was lower in the winter of the decrease phase as compared to the increase phase. The return rate of voles, a proxy of survival, was also lower in the decrease than in the increase phase of the cycle and positively related to haematocrit levels. Almost 90% of all green vegetation shoots were consumed by voles during the winter of the decrease phase while only two thirds were eaten in the increase phase. Our results suggest that the winter decrease phase of cyclic vole populations is associated with both a deterioration in the physiological condition of voles and a significant depletion of winter food resources. This implies that malnutrition induces poor physiological condition in voles, which in turn may increase mortality either directly through starvation or indirectly through increased susceptibility to predators and pathogens. [source] | ||||||||||