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We compared Snowy Owl feeding ecology from 15 breeding season studies throughout Nearctic and Palearctic circumpolar regions. We used raw data and information theory to assess the owls’ feeding niche. Combined studies yielded 59,923 prey items, of which 59,585 were used for calculations. Overall, mean food niche breadth (FNB) was narrow: H′ = 1.95; R = 1.60, D = 0.526. In 10 of 15 studies, lemmings were > 71.8% of the owls’ diet. In four studies, Lemmus was > 90% of the diet, and in three studies Dicrostonyx was >90% of the diet. In three other studies, Lemmus represented 71.8%, 73.8%, and 84.0% of the diet. In one study, Lemmus and Dicrostonyx were about equal: 49.1% and 47.5%. In the four remaining studies, Microtus and Clethrionomys voles were important. In contrast, of 5888 winter prey items from seven North American studies, the mean FNB (H′ = 4.61) was twice that of 15 breeding season scores, FNB (H’ = 1.95). The Snowy Owl is primarily an obligate lemming predator for breeding. Changes to population ecology and distribution of lemmings due to climate change will have direct affects and effects on the Snowy Owls’ reproductive output. The conservation of Snowy Owls is the conservation of lemmings.

Simple Summary: It is common knowledge that Snowy Owls eat lemmings during the nesting season, and it is believed that lemming populations fluctuate dramatically over several years, often termed a cycle. When lemming populations reach high densities, Snowy Owls have a highly successful breeding season, producing numerous young per nest. This successful nesting results in large numbers of young Snowy Owls migrating south during their first winter. This movement, generally called an irruption migration, has been known for over a century, and stirs the admiration of the public. Indeed, each time an irruption migration happens, it is among the most popular wildlife viewing events in North America. Given this predator–prey relationship between Snowy Owls and lemmings, we were interested in quantifying how important lemmings were to Snowy Owls throughout their worldwide breeding range. Of the 15 studies we reviewed, 59,923 prey items were recorded. Lemmings were clearly the most important food source for breeding Snowy Owls, but voles were sometimes also important. Given the near obligate dependency on lemmings for breeding, one wonders how a changing climate will affect lemming populations and distribution, and consequently Snowy Owl breeding. And, will this affect the Snowy Owl breeding population, resulting in fewer young Snowy Owls migrating south during an irruption migration. We compared Snowy Owl feeding ecology from 15 breeding season studies throughout Nearctic and Palearctic circumpolar regions. We used raw data and information theory to assess the owls' feeding niche. Combined studies yielded 59,923 prey items, of which 59,585 were used for calculations. Overall, mean food niche breadth (FNB) was narrow: H′ = 1.95; R = 1.60, D = 0.526. In 10 of 15 studies, lemmings were > 71.8% of the owls' diet. In four studies, Lemmus was > 90% of the diet, and in three studies Dicrostonyx was >90% of the diet. In three other studies, Lemmus represented 71.8%, 73.8%, and 84.0% of the diet. In one study, Lemmus and Dicrostonyx were about equal: 49.1% and 47.5%. In the four remaining studies, Microtus and Clethrionomys voles were important. In contrast, of 5888 winter prey items from seven North American studies, the mean FNB (H′ = 4.61) was twice that of 15 breeding season scores, FNB (H' = 1.95). The Snowy Owl is primarily an obligate lemming predator for breeding. Changes to population ecology and distribution of lemmings due to climate change will have direct affects and effects on the Snowy Owls' reproductive output. The conservation of Snowy Owls is the conservation of lemmings. [ABSTRACT FROM AUTHOR]

Abstract—Features of the breeding and population structure of the root vole inhabiting the Southern Trans-Ural region during the periods of 1981–2001 and 2020–2022 are considered. Animals were captured during both winter and snowless periods. A total of 754 root voles were captured using ditches with pitfalls (guide fences made of polyethylene film) and trap lines. As in the other parts of their range, root voles in the Southern Trans-Ural region prefer near-water habitats. Winter breeding is characteristic of this rodent in the Southern Trans-Ural region, but the most intensive breeding is observed in May–June. These months are also characterized by the maximum fecundity for both overwintered and young females. Overwintered females can produce up to four litters during their reproductive period, while young females can produce 3–4 litters. The fecundity of overwintered females is statistically significantly higher than that of young ones. In the months February–May, overwintered animals dominate in the root vole population, while in June and the following summer and autumn months, underyearlings predominate. Males dominate among the overwintered and underyearling animals; at the end of summer and in the autumn, the sex ratio among these age groups of root voles levels off. [ABSTRACT FROM AUTHOR]

In the present study, we analysed the variation of breeding parameters and the diet composition of the Common Barn-owl (Tyto alba) in three different demographic phases of the Common Vole (Microtus arvalis) in a complete population cycle between two outbreaks. The study was conducted in the south-eastern part of the Transdanubian region in South Hungary. For the analysis, we used data of 81 randomly selected first clutches from 2015 to 2019, a time period which represented a full demographic cycle of the Common Vole after the 2014 outbreak with an exceptionally high peak. We tested the impact of prey abundance and diversity of diet composition as continuous predictors as well as the demographic phase of Common Vole and the mesoregion as categorical explanatory variables on the measured reproductive outputs as response variables using Generalized Linear Models (GLM). Considering the breeding parameters, the number of fledglings, and fledging and reproductive success were significantly higher in the increase phase than during the vole crash phase. Based on GLM models, our results demonstrated that the clutch size of the Common Barn-owl is determined ultimately by the availability and consumption rate of the Common Vole as main prey, while other small mammal prey categories did not affect the clutch size. These results support the finding that the clutch size of vole-eating raptors and owls, which begin breeding periods in early spring predicts the vole abundance in this early spring period. Considering the other investigated small mammal prey groups, the alternative prey role was confirmed only in case of the Murid rodent prey categories (Apodemus spp., Muridae). [ABSTRACT FROM AUTHOR]

In the present study, we analysed the variation of breeding parameters and the diet composition of the Common Barn-owl (Tyto alba) in three different demographic phases of the Common Vole (Microtus arvalis) in a complete population cycle between two outbreaks. The study was conducted in the south-eastern part of the Transdanubian region in South Hungary. For the analysis, we used data of 81 randomly selected first clutches from 2015 to 2019, a time period which represented a full demographic cycle of the Common Vole after the 2014 outbreak with an exceptionally high peak. We tested the impact of prey abundance and diversity of diet composition as continuous predictors as well as the demographic phase of Common Vole and the mesoregion as categorical explanatory variables on the measured reproductive outputs as response variables using Generalized Linear Models (GLM). Considering the breeding parameters, the number of fledglings, and fledging and reproductive success were significantly higher in the increase phase than during the vole crash phase. Based on GLM models, our results demonstrated that the clutch size of the Common Barn-owl is determined ultimately by the availability and consumption rate of the Common Vole as main prey, while other small mammal prey categories did not affect the clutch size. These results support the finding that the clutch size of vole-eating raptors and owls, which begin breeding periods in early spring predicts the vole abundance in this early spring period. Considering the other investigated small mammal prey groups, the alternative prey role was confirmed only in case of the Murid rodent prey categories (Apodemus spp., Muridae). [ABSTRACT FROM AUTHOR]

The maximum rate of aerobic exercise metabolism (VO 2 max) is a trait informative from both medical and evolutionary perspective, and both the physiological mechanisms limiting its level and its evolution are subject to vivid debate. Both comparative analyses and studies on the effects of training or acclimation to aerobically-demanding conditions suggest a role of oxygen transport-related properties of blood in limiting VO 2 max. Here we used a unique experimental evolution model – lines of bank voles selected for high rate of swim-induced aerobic metabolism (VO 2 swim; A lines), which evolved a 60% higher VO 2 swim than that observed in unselected control lines (C) – and asked how the hematological parameters evolved in response to the selection. Voles from the A lines had a decreased hemoglobin concentration in cardiac blood samples (adjusted means ± SE, A: 14.7 ± 1.1, C: 15.3 ± 1.1 g/dl; p =.008), hematocrit (A: 51.7 ± 4.5, C: 53.8 ± 4.2%; p =.042) and tended to have less erythrocytes per microliter of blood (A: 11.5 ± 1.4, C: 12.7 ± 1.3 mln/μl; p =.083). The effect of selection was more pronounced in males than in females. Thus, selection for high aerobic-exercise performance resulted in a paradoxical decrease in traits positively associated with oxygen-carrying capacity per unit of blood volume, and the effect was sex-dependent. However, as a decreased blood viscosity associated with the lowered hematocrit reduces the costs of blood circulation, it can be hypothesized that the change can actually boost the oxygen supply to peripheral tissues. • The artificial selection resulted in a 60% increase of aerobic exercise metabolism. • The correlated response in hematological parameters was sex-specific. • Hematocrit and hemoglobin concentration decreased in males from the selected lines. [ABSTRACT FROM AUTHOR]

Voles are key mammals in understanding how social interactions can affect large-scale population processes. Previous studies have shown that at high population densities, meadow voles (Microtus pennsylvanicus) have a lower proportion of breeding animals, higher average corticosterone levels, and can be limited by female territorial spacing. Based on this, we compared corticosterone levels and spatial use between breeding and nonbreeding free-ranging adult meadow voles within populations. We measured intrasexual spatial overlap to examine if breeding females minimize occupying the same areas as other females, and noninvasively assessed corticosterone levels using fecal corticosterone metabolites (FCMs). We found that female meadow voles have much lower intrasexual spatial overlap than males, even though both sexes have similar range sizes, and that females have generally higher FCM levels than males. However, breeding and nonbreeding females did not differ from one another in spatial use or in FCM levels. Conversely, reproductive classes of males differed greatly in all measures: nonbreeding males had FCM levels that were two times higher than those of breeding males, occupied a smaller range, and had lower spatial overlap, indicating they were moving less widely than breeding males. We additionally validated an enzyme immunoassay for noninvasively measuring FCMs in meadow voles. The assay was successful in detecting an increase in corticosterone stimulated by adrenocorticotropic hormone injection; however, dexamethasone did not induce negative feedback. FCMs reflect circulating corticosterone levels approximately 5 h prior. These results highlight differences in FCMs and spacing in meadow voles related to sex and reproductive status, and reflect the respective strategies males and females employ during the breeding season. [ABSTRACT FROM AUTHOR]

Here I describe the first confirmed breeding of the Red-footed Falcon (Falco vespertinus) in the Czech Republic after 1973. In 2019, a pair of the Red-footed Falcon bred in a rural landscape near Hrdibořice (Olomouc region, mapping square 6569), while five young successfully fledged. Such a unique breeding event of the Red-footed Falcon in the Czech Republic may correspond with an increase of the breeding populations in Hungary and Slovakia, as well as with a parallel population peak of the Common Vole (Microtus arvalis) - the important component of the Red-footed Falcon diet. [ABSTRACT FROM AUTHOR]

Dispersal is one of the most important, yet least understood phenomena of evolutionary ecology. Triggers and consequences of dispersal are difficult to study in natural populations since dispersers can typically only be identified a posteriori. Therefore, a lot of work on dispersal is either of a theoretical nature or based on anecdotal observation. This is especially true for cryptic species such as small mammals. We conducted an experiment on the common vole, Microtus arvalis, in semi-natural enclosures and investigated the spatial and genetic establishment success of residents and dispersers in their natal and new populations. Our study uses genetic data on the reproductive success of 1255 individuals to measure the fitness trajectories of the residents and dispersing individuals. In agreement with past studies, we found that dispersal was highly male-biased, and was most probably induced by the agonistic encounters with conspecifics, suggesting it could act as an inbreeding avoidance mechanism. There was low breeding success of dispersers into new populations. Although nearly 26% of identified dispersers reproduced in their natal populations, only seven percent reproduced in the new populations. Settlement appeared to be a pre-requisite for reproduction in both sexes, and animals that did not spatially settle into a new population dispersed again, usually on the same day of immigration. In the event that dispersers reproduced in the new population, they did so at relatively low population densities. We also found age-related differences between the sexes in breeding success, and male dispersers that subsequently established in the new population were young individuals that had not reproduced in their natal population, whereas successful females had already reproduced in their natal population. In conclusion, with our detailed field data on establishment and substantial parentage assignments to understand breeding success, we were able to gain an insight into the fitness of dispersers, and how the two sexes optimise their fitness. Taken together, our results help to further understand the relative advantages and costs of dispersal in the common vole. [ABSTRACT FROM AUTHOR]

We used a 13-year time series of abundance estimates of breeding Northern Saw-whet Owls ( Aegolius acadicus), and of small mammals from central Ontario, Canada, to assess the numerical response of the owls to small-mammal prey species. We found that the finite rate of increase of breeding owls was directly related to estimates of red-backed vole ( Myodes gapperi) abundance. Thus, it appeared that the owls were nomadic, and made decisions about where to breed based on vole supply. The owls showed a much weaker response to deer mouse ( Peromyscus maniculatus) abundance. Across all years, 55% of variation in owl rate of increase could be uniquely attributed to vole abundance, whereas only 3% could be attributed to mouse abundance. Consistent with the model of nomadism, there was only a weak relationship between the proportion of hatch-year owls caught at fall banding stations, and small-mammal abundance. Instead, it appeared that Northern Saw-whet Owls avoided years of widespread reproductive failure through the nomadic strategy of selecting breeding sites based on vole supply. [ABSTRACT FROM AUTHOR]

We determined whether seasonal differences exist in the amount of time meadow voles, Microtus pennsylvanicus, self-groom when they encounter the scents of conspecifics. To do so, we used voles that were born and reared under long photoperiod (LP) and short photoperiod (SP). LP voles represent those found in free-living populations during the spring and summer breeding season, whereas SP voles characterize those found in free-living populations during the fall and winter nonbreeding season. Experiment 1 showed that LP male and female voles self-groomed more in response to odors of LP opposite-sex conspecifics as compared to those of other LP and SP conspecifics, suggesting that they may be self-grooming to signal sexual interest or excitement to potential mates. Experiment 2 demonstrated that SP males self-groomed more in response to scents of LP female voles and those of SP males as compared to scents of LP males and SP females, whereas SP females spent similar amounts of time self-grooming in response to scents of LP males, LP females, SP females, and SP males. These seasonal differences in self-grooming may reflect differences in the messages produced by groomers when they broadcast their odors as well as differences in the meaning of such odors to opposite-sex conspecifics. Alternatively, these data may be associated with seasonal differences in sexual motivation of the groomers when exposed to scents of particular conspecifics. [ABSTRACT FROM AUTHOR]

The paper investigates effects of kin recognition on estrus and breeding in mandarin voles, microtus mandarinus, in the laboratory using a cross-fostering method. Nonsiblings reared apart produced significantly more litters than siblings or nonsiblings reared together. These results may support the hypothesis that familiarity through association before weaning, plays an important role in kin recognition. On the other hand, nonsiblings reared apart produced significantly more litters than siblings reared apart. These observations show that phenotype-matching mechanisms of kin recognition may operate in conjunction with familiarity in kin recognition in this species.

In recent years, three related methods have been used to model the phenotypic dynamics of traits under the influence of natural selection. The first is based on an approximation to quantitative genetic recursion equations for sexual populations. The second is based on evolution in asexual lineages with mutation-generated variation. The third method finds an evolutionarily stable set of phenotypes for species characterized by a given set of fitness functions, assuming that the mode of reproduction places no constraints on the number of distinct types that can be maintained in the population. The three methods share the property that the rate of change of a trait within a homogeneous population is approximately proportional to the individual fitness gradient. The methods differ in assumptions about the potential magnitude of phenotypic differences in mutant forms, and in their assumptions about the probability that invasion or speciation occurs when a species has a stable, yet invadable phenotype. Determining the range of applicability of the different methods is important for assessing the validity of optimization methods in predicting the evolutionary outcome of ecological interactions. Methods based on quantitative genetic models predict that fitness minimizing traits will often be evolutionarily stable over significant time periods, while other approaches suggest this is likely to be rare. A more detailed study of cases of disruptive selection might reveal whether fitness-minimizing traits occur frequently in natural communities. [ABSTRACT FROM AUTHOR]

Investigates the dynamics of predator-prey cycles by changing breeding strategies. Effects of predators-prey responses on population density; Impact of breeding suppression on the stability of the cycle; Discussion of the anti-predatory behavior of voles; Variability in animal breeding effort according to the phase of the cycle.

The breeding biology of the bank vole was studied in northern and southern populations in Sweden in the years 1973-76. Trapped specimens supplied organ weights and histological data, which were utilized to describe the breeding season, number and size of litters, reproductive losses, spermatogenesis, and sexual maturation. In the north the populations are cyclic. During the increase phase of the cycle the breeding season was long, litter sizes and gonad weights were large, and there was maturation of yearlings in the summer. During the peak phase reproduction was impaired in all these respects. In southern Sweden there was no cyclicity, and the reproductive events varied less, but in 1976 the litters were larger than usual and the season was much extended. In the south the voles born during the early part of the season regularly became sexually mature during their first summer. The differences in reproductive biology are related to population dynamics and discussed in terms of different hypotheses concerning vole population cyclicity. [ABSTRACT FROM AUTHOR]

An introduction is presented which discusses reports on relationship between corticosterone levels and spatial overlap of breeding and nonbreeding in meadow voles, natural selection in mammals, and mammals in Iran.

The article discusses polymorphic microsatellite clones from the grey backed vole, Clethrionomys rufocanus bedfordiae, which is a species with frequent population fluctuations. The authors refer to a preliminary study on ten voles with five of ten microsatellites that are polymorphic. The study observed eighty one voles with five microsatellite alleles at loci differing in number of repeat units. The results of the four loci that were used to estimate the heterozygosity suggested that the vole population is subject to random mating. According to the authors, inbreeding linked to a gene subject to assertive mating was not amplified with primers used.