Bank Voles Research Articles

Host in reserve: The role of common shrews (Sorex araneus) as a supplementary source of tick hosts in small mammal communities influenced by rodent population cycles.

Rodents often act as important hosts for ticks and as pathogen reservoirs. At northern latitudes, rodents often undergo multi‐annual population cycles, and the periodic absence of certain hosts may inhibit the survival and recruitment of ticks. We investigated the potential role of common shrews (Sorex araneus) to serve as a supplementary host source to immature life stages (larvae and nymphs) of a generalist tick Ixodes ricinus and a small mammal specialist tick I. trianguliceps, during decreasing abundances of bank voles (Myodes glareolus). We used generalized mixed models to test whether ticks would have a propensity to parasitize a certain host species dependent on host population size and host population composition across two high‐latitude gradients in southern Norway, by comparing tick burdens on trapped animals. Host population size was defined as the total number of captured animals and host population composition as the proportion of voles to shrews. We found that a larger proportion of voles in the host population favored the parasitism of voles by I. ricinus larvae (estimate = −1.923, p = .039) but not by nymphs (estimate = −0.307, p = .772). I. trianguliceps larvae did not show a lower propensity to parasitize voles, regardless of host population composition (estimate = 0.875, p = .180), while nymphs parasitized shrews significantly more as vole abundance increased (estimate = 2.106, p = .002). These results indicate that common shrews may have the potential to act as a replacement host during periods of low rodent availability, but long‐term observations encompassing complete rodent cycles may determine whether shrews are able to maintain tick range expansion despite low rodent availability.

Changes in the Hippocampus of the Bank Vole Due to Population Density Dynamics

Changes in the Hippocampus of the Bank Vole Due to Population Density Dynamics

Yersinia enterocolitica in wild and peridomestic rodents within Great Britain, a prevalence study.

Yersinia enterocolitica is a human pathogen transmitted via the faecal-oral route among animals and humans and is a major foodborne public health hazard. This study explores the role of Y.enterocolitica transmission at the livestock-wildlife interface and investigates the potential role wild and peridomestic rodents play as a source of this zoonotic pathogen. The total of 342 faecal samples collected from the seven rodent species and one insectivore was examined using an optimized protocol to culture and identify Y.enterocolitica. Positive samples were also bioserotyped for grouping and determination of sample pathogenicity. Wildlife species sampled in this study were separated into two sample groups: randomly sampled (brown rats, house mice, wood mice, bank voles, field voles and the common shrew), as well as targeted sampling (red and grey squirrels). The overall prevalence of Y.enterocolitica in the randomly sampled population was 3.73%. Brown rats were chosen as sentinel species and tested to determine if location (pig farm vs non-pig farm) was a significant factor affecting Y.enterocolitica prevalence. In this study, location was not significant. All positive samples were found to be of biotype 1A, deemed non-pathogenic. Three of the samples were serotype 09, six were serotype 27 and five had an unidentifiable serotype. This study represents the first time Y.enterocolitica has been identified in these species of wildlife within mainland Britain. In addition, this study's findings are entirely novel and overall with regard to field voles and common shrews. However, the role of wild and peridomestic rodents in the transmission of pathogenic Y.enterocolitica remains unknown, as this study was unable to detect the presence of pathogenic Y.enterocolitica strains in these species.

Morphological and Molecular Description of Sarcocystis myodes n. sp. from the Bank Vole (Clethrionomys glareolus) in Lithuania

Simple SummaryRepresentatives of genus Sarcocystis (Apicomplexa, Sarcocystidae) are parasites of mammals, birds, and reptiles. They are characterized by two-host prey-predator life cycle. Rodents are reservoirs of zoonotic diseases and play a significant role in a spread of pathogens. At present, about 40 Sarcocystis species are known to form sarcocysts in muscles and brain of rodents. Most of Sarcocystis spp. in these hosts have been characterized by morphological methods and life cycle investigations. In the present study a new Sarcocystis species, S. myodes is described in skeletal muscles of the bank voles (Clethrionomys glareolus) from Lithuania using morphological, molecular, and phylogenetic analysis. Based on five genetic loci, S. myodes was most closely related to Sarcocystis spp. using predatory mammals as their definitive hosts. The analysis of previous studies indicates that Sarcocystis spp. diversity in voles is not fully revealed. Furthermore, some Sarcocystis spp. formerly detected in voles are important pathogens. Therefore, further molecular examinations are needed for the revision of Sarcocystis spp. in these hosts.Numerous rodent species have been broadly examined for Sarcocystis parasites. Nevertheless, recent investigations on Sarcocystis spp. in voles are lacking. As many as 45 bank voles (Clethrionomys glareolus) captured in several locations in Lithuania were examined in the present study. Based on morphological, genetic, and phylogenetic results, sarcocysts detected in one bank vole were described as Sarcocystis myodes n. sp. Using light microscopy analysis, the observed sarcocysts were ribbon-shaped, 6000–3000 × 70–220 µm in size. Sarcocysts were characterized by a relatively thin (about 1 μm) and apparently smooth cyst wall. The lancet-shaped bradyzoites were 9.6–12.0 × 3.1–4.6 μm in size. By transmission electron microscopy, the sarcocyst wall was up to 1 μm thick, parasitophorous vacuolar membrane had small knob-like blebs. Based on 18S rDNA, 28S rDNA, cox1, rpoB, and ITS1 loci, S. myodes showed highest similarity with S. ratti from the black rat (Rattus rattus). According to phylogenetic placement, S. myodes was most closely related to Sarcocystis spp. that employ predatory mammals as their definitive hosts. Morphologically, sarcocysts of S. myodes have similar features to those of S. cernae, S. dirumpens, and S. montanaensis described in voles, however, they use birds of prey or snakes as their definitive hosts.

Цитогенетичні дослідження Myodes Glareolus з природних популяцій Чорнобильської зони відчуження у віддалений післяаварійний період

The results of cytogenetic studies of bank voles (Myodes glareolus) carried out during 2009 - 2016 in the areas of the Chornobyl Exclusion Zone with different levels of radionuclide contamination are presented. In the remote period after the Chornobyl accident features of chromosomal instability in somatic cells of examined animals, manifested as elevated levels of bone marrow cells with micronuclei, are observed. Probably, they can be caused by transgenerational radiation-induced chromosomal instability and changes in the ecological characteristics of the population under the combined impact of chronic low-intensity radiation and negative environmental factors.

Cluster of human Puumala orthohantavirus infections due to indoor exposure?-An interdisciplinary outbreak investigation.

Puumala orthohantavirus (PUUV) is the most important hantavirus species in Europe, causing the majority of human hantavirus disease cases. In central and western Europe, the occurrence of human infections is mainly driven by bank vole population dynamics influenced by beech mast. In Germany, hantavirus epidemic years are observed in 2‐ to 5‐year intervals. Many of the human infections are recorded in summer and early autumn, coinciding with peaks in bank vole populations. Here, we describe a molecular epidemiological investigation in a small company with eight employees of whom five contracted hantavirus infections in late 2017. Standardized interviews with employees were conducted to assess the circumstances under which the disease cluster occurred, how the employees were exposed and which counteractive measures were taken. Initially, two employees were admitted to hospital and serologically diagnosed with hantavirus infection. Subsequently, further investigations were conducted. By means of a self‐administered questionnaire, three additional symptomatic cases could be identified. The hospital patients' sera were investigated and revealed in one patient a partial PUUV L segment sequence, which was identical to PUUV sequences from several bank voles collected in close proximity to company buildings. This investigation highlights the importance of a One Health approach that combines efforts from human and veterinary medicine, ecology and public health to reveal the origin of hantavirus disease clusters.

Human antibody recognizing a quaternary epitope in the Puumala virus glycoprotein provides broad protection against orthohantaviruses.

The rodent-borne hantavirus Puumala virus (PUUV) and related agents cause hemorrhagic fever with renal syndrome (HFRS) in humans. Other hantaviruses, including Andes virus (ANDV) and Sin Nombre virus, cause a distinct zoonotic disease, hantavirus cardiopulmonary syndrome (HCPS). Although these infections are severe and have substantial case fatality rates, no FDA-approved hantavirus countermeasures are available. Recent work suggests that monoclonal antibodies may have therapeutic utility. We describe here the isolation of human neutralizing antibodies (nAbs) against tetrameric Gn/Gc glycoprotein spikes from PUUV-experienced donors. We define a dominant class of nAbs recognizing the "capping loop" of Gn that masks the hydrophobic fusion loops in Gc. A subset of nAbs in this class, including ADI-42898, bound Gn/Gc complexes but not Gn alone, strongly suggesting that they recognize a quaternary epitope encompassing both Gn and Gc. ADI-42898 blocked the cell entry of seven HCPS- and HFRS-associated hantaviruses, and single doses of this nAb could protect Syrian hamsters and bank voles challenged with the highly virulent HCPS-causing ANDV and HFRS-causing PUUV, respectively. ADI-42898 is a promising candidate for clinical development as a countermeasure for both HCPS and HFRS, and its mode of Gn/Gc recognition informs the development of broadly protective hantavirus vaccines.

Eco-epidemiological screening of multi-host wild rodent communities in the UK reveals pathogen strains of zoonotic interest.

Wild rodent communities represent ideal systems to study pathogens and parasites shared among sympatric species. Such studies are useful in the investigation of eco-epidemiological dynamics, improving disease management strategies and reducing zoonotic risk. The aim of this study was to investigate pathogen and parasites shared among rodent species (multi-host community) in West Wales in an area where human/wildlife disease risk was not previously assessed. West Wales is predominantly rural, with human settlements located alongside to grazing areas and semi-natural landscapes, creating a critical human-livestock-wildlife interface. Ground-dwelling wild rodent communities in Wales were live-trapped and biological samples – faeces and ectoparasites – collected and screened for a suite of pathogens and parasites that differ in types of transmission and ecology. Faecal samples were examined to detect Herpesvirus, Escherichia coli, and Mycobacterium microti. Ticks and fleas were collected, identified to species based on morphology and genetic barcodes, and then screened for Anaplasma phagocytophilum, Babesia microti, Borrelia burgdorferi sensu lato, and Bartonella sp. All the pathogens and parasites screened pose a characteristic epidemiological challenge, such as variable level of generalism, unknown zoonotic potential, and lack of data. The results showed that the bank vole Myodes glareolus had the highest prevalence of all pathogens and parasites. Higher flea species diversity was detected than in previous studies, and at least two Bartonella species were found circulating, one of which has not previously been detected in the UK. These key findings offer new insights into the distribution of selected pathogen and parasites and subsequent zoonotic risk, and provide new baselines and perspectives for further eco-epidemiological research.

Seasonal peculiarities of PCDD/Fs levels in bank voles inhabiting sites in the vicinity of the landfill with municipal wastes (Moscow, Russia).

Differences in PCDD/Fs concentrations were registered among adult bank voles (Myodes glareolus) inhabiting forest in the vicinity of the Landfill Salariyevo (Moscow, Russia) and caught in early spring (over-winter survivors) and late summer. The levels of highly toxic congeners and WHO-TEQ05 in samples of wintering voles were much lower than those in samples got in summer. This difference was investigated analyzing PCDD/Fs in sexually matured animals and offspring obtained in vivarium. Practically, no significant differences of PCDD/Fs concentrations and general toxicity were revealed among sexes. The main impact to these seasonal differences in PCDD/Fs accumulation was assigned to the types of functional development and activity, diet variation as natural growth of all voles occurs on the same territory but in seasonally diverse conditions. So, the species functional ecology (lifestyle and seasonal features) should be considered in practical application of animal models from natural populations for local monitoring of PCDD/Fs body burden, and individual functional type of ontogenesis among cyclomorphic mammalian species, especially. Thus, the results obtained during monitoring should be carefully interpreted for a proper environmental management.

Artificial selection for predatory behaviour results in dietary niche differentiation in an omnivorous mammal.

The diet of an individual is a result of the availability of dietary items and the individual's foraging skills and preferences. Behavioural differences may thus influence diet variation, but the evolvability of diet choice through behavioural evolution has not been studied. We used experimental evolution combined with a field enclosure experiment to test whether behavioural selection leads to dietary divergence. We analysed the individual dietary niche via stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) in the hair of an omnivorous mammal, the bank vole, from four lines selected for predatory behaviour and four unselected control lines. Predatory voles had higher hair δ15N values than control voles, supporting our hypothesis that predatory voles would consume a higher trophic level diet (more animal versus plant foods). This difference was significant in the early but not the late summer season. The δ13C values also indicated a seasonal change in the consumed plant matter and a difference in food sources among selection lines in the early summer. These results imply that environmental factors interact with evolved behavioural tendencies to determine dietary niche heterogeneity. Behavioural selection thus has potential to contribute to the evolution of diet choice and ultimately the species' ecological niche breadth.

Analysis of Puumala orthohantavirus Genome Variants Identified in the Territories of Volga Federal District.

Hemorrhagic fever with renal syndrome (HFRS) is a zoonotic disease commonly diagnosed in the Volga Federal District (VFD). HFRS is caused by Puumala orthohantavirus (PUUV), and this virus is usually detected in bank voles as its natural host (Myodes glareolus). The PUUV genome is composed of the single-stranded, negative-sense RNA containing three segments. The goal of the current study is to identify genome variants of PUUV strains circulating in bank voles captured in the Udmurt Republic (UR) and Ulyanovsk region (ULR). The comparative and phylogenetic analysis of PUUV strains revealed that strains from Varaksino site UR are closely related to strains previously identified in the Pre-Kama area of the Republic of Tatarstan (RT), whilst strains from Kurlan and Mullovka sites ULR are similar to strains from the Trans-Kama area of the RT. It was also found that Barysh ULR strains form a separate distinct group phylogenetically equidistant from Varaksino and Kurlan–Mullovka groups. The identified groups of strains can be considered as separate sub-lineages in the PUUV Russian genetic lineage. In addition, the genomes of the strains from the UR, most likely, were formed as a result of reassortment.

Hantavirus Disease: An Update

In addition to the well-known clinical early symptoms of hantavirus disease (fever, flank and abdominal pain as well as arthralgia), unusual neurological changes in the context of infection come into focus. The spectrum of neurological symptoms ranges from transient myopia to severe pareses in the context of Guillain-Barré syndrome. In endemic areas, rapid IgM tests for initial assessment are of certain value for differential diagnosis. For therapeutic approaches, only supportive measures up to transient dialysis are available.Molecular genetic analysis and comparison of hantavirus strains of patients and mice from the same geographical area allowed molecular characterization of different outbreak regions. In the meantime, the Puumala viruses of the main outbreak regions in Germany are molecularly well characterized; therefore, the nucleotide sequence of the virus strain detected in a patient makes it possible to draw conclusions about the geographic region where the patient's infection took place.The human pathogenic hantaviruses being prevalent in Germany are the Puumala virus (reservoir: bank vole) and the Dobrava-Belgrade virus, genotype Kurkino (reservoir: striped field mouse). Recently, the molecular detection of further hantaviruses in patients with hantavirus disease was achieved. It can be concluded that also the Seoul virus (reservoir: rats) and the Tulavirus (reservoir: field mouse and related species) occasionally cause hantavirus disease in Germany.New results revealed that human infections can occur not only by the generally accepted route of inhalation of virus-containing aerosols, but also by ingestion of virus-containing materials.For patients with hantavirus infection or disease, it can be assumed that they are not infectious for their environment. A new systematic review could not confirm a human-to-human transmission previously postulated for South American hantaviruses.While all known human pathogenic hantaviruses are transmitted by rodents, other hantaviruses have been recently detected in shrews, moles, and bats. The clinical significance of these new viruses is quite unclear as yet.

Cocirculation of Leptospira spp. and multiple orthohantaviruses in rodents, Lithuania, Northern Europe.

In Europe, zoonotic Leptospira spp. and orthohantaviruses are mainly associated with specific rodent hosts. These pathogens cause febrile human diseases with similar symptoms and disease progression. In Lithuania, the presence of Dobrava-Belgrade orthohantavirus (DOBV), Tula orthohantavirus (TULV) and Leptospira spp. in rodent reservoirs is still unknown, and Puumala orthohantavirus (PUUV) was detected in bank voles (Clethrionomys glareolus) at only one site. Therefore, we collected and screened 1617 rodents and insectivores from Lithuania for zoonotic (re-)emerging Leptospira and orthohantaviruses. We detected Leptospira DNA in six rodent species, namely striped field mouse (Apodemus agrarius), yellow-necked mouse (Apodemus flavicollis), bank vole, common vole (Microtus arvalis), field vole (Microtus agrestis) and root vole (Microtus oeconomus). Leptospira DNA was detected with an overall mean prevalence of 4.4% (range 3.7%-7.9% per rodent species). We detected DOBV RNA in 5.6% of the striped field mice, PUUV RNA in 1% of bank voles and TULV RNA in 4.6% of common voles, but no Leptospira DNA in shrews and no hantavirus-Leptospira coinfections in rodents. Based on the complete coding sequences of the three genome segments, two distant DOBV phylogenetic lineages in striped field mice, one PUUV strain in bank voles and two TULV strains in common voles were identified. The Leptospira prevalence for striped field mice and yellow-necked mice indicated a significant negative effect of the distance to water points. The detection of (re-)emerging human pathogenic Leptospira and three orthohantaviruses in rodent reservoirs in Lithuania calls for increased awareness of public health institutions and allows the improvement of molecular diagnostics for pathogen identification.

Molecular Analysis of Puumala orthohantavirus Strains in Hemorrhagic Fever with Renal Syndrome Patients in Tatarstan

<h3>Purpose</h3> <i>Puumala</i> hantavirus (PUUV) is the main causative agent of hemorrhagic fever with renal syndrome (HRFS) in the Republic of Tatarstan (RT). The natural host of PUUV is the bank vole (<i>Myodes glareolus</i>), where virus establishes life-long infection. The goal of this work was to identify the PUUV strains in HFRS patients from Kazan and search for related strains circulating in the bank vole populations in RT. <h3>Methods & Materials</h3> Total RNA was extracted from HFRS blood samples. The overlapping PCR-products were obtained by RT-PCR using S segment specific primers and automated sequencing. <h3>Results</h3> The PUUV RNA was detected in three HFRS samples. Analysis of a complete PUUV S segment coding region (1302 bp) revealed high genetic identity (99.7%) between GL436 and GL437 HFRS strains. Sequence identity between these two strains and GL427 strain was within 92.2-92.3% range. Strains GL436 and GL437 were 99.5-99.8% similar to PUUV strains previously identified in RT. Also, these strains clustered with the RUS genetic lineage, which was shown to circulate in the bank vole population near Kazan. Therefore, it could be suggested that these two HFRS patients were infected in the same region near Kazan. Surprisingly, the sequence identity between GL427 strain and other PUUV strains of the RUS lineage was lower, ranging between 90.6-92.4%. Therefore, the source of this PUUV strain remains unknown. <h3>Conclusion</h3> Sequence analysis revealed a potential link between PUUV strains detected in HFRS patients and circulating in the bank vole population near Kazan. These data suggest that molecular methods could be used to identify the regions where human infection is highly likely.

Radiation-induced effects on bone marrow of bank voles inhabiting the Chornobyl exclusion zone

Purpose To investigate the effects of chronic exposure to low-dose radiation on bone marrow hematopoiesis of bank voles inhabiting the radioactively contaminated territory of the Chornobyl exclusion zone. Materials and methods Animals were collected within the highly radioactive area of the so-called Red Forest located close to the destroyed 4th reactor of the Chornobyl Nuclear Power Plant. Radioecological investigations included evaluation of radiocontamination of soil samples by 90Sr and 137Cs, levels of incorporated radionuclides in animals’ bodies and organs, as well as the absorbed dose rates. The study of peripheral blood and bone marrow parameters combined with cytogenetic analysis of bone marrow micronucleated polychromatic erythrocytes and standard metaphase test was carried out. Results The blood system of the exposed animals manifested significant changes in peripheral blood parameters (anaemia and leucocyte formula left shift), ineffective differentiation and maturation of bone marrow cells, particularly relevant to the erythroid and granulocyte pools. Increased yields of bone marrow micronucleated polychromatic erythrocytes and chromosomal aberrations, including dicentrics and Robertsonian fusion-like configurations, were revealed. Conclusions Observed disturbances in the bone marrow and peripheral blood suggest functional instability and inefficient compensatory and recovery reactions of the blood system of the bank voles from the contaminated areas of the Chornobyl exclusion zone. We assume that they are the consequences both of direct radiation exposure and hereditary pathological changes that have formed in a number of generations inhabiting radioactively contaminated areas.

PROPOZYCJA MONITORINGU NORNICY RUDEJ (MYODES GLAREOLU, SCHREBER 1780)

There are many reasons why it might be necessary to monitor the bank voles. It causes damage to trees and eats seeds in orchards and tree plantations, and the determination of its presence as well as the effectiveness of the measures taken to minimize losses is very important in the activity of the above-mentioned. The rodent is also the main for central Europe reservoir of the Puumala virus, which is dangerous to humans, so observing the trends in the number of voles may be crucial. The small number of the species may indicate environmental poisoning, especially with copper. And finally, it is a very important species for the environment, both transformed by man and natural, so it is very important to preserve it despite the climate changes. The bank vole is a small mammal from the Cricetidae family. It occurs all over Europe. It lives mainly in deciduous forests of medium density and rich undergrowth, although it is also found in other areas, including anthropogenic ones. The proposed monitoring is based on catching with the use of wooden box traps and the analysis of pellets. The indicators used would be: the number of individuals caught per 100 trap-nights, the percentage of the species in total number of small mammals and the age structure of the population. In the first method one should remember about practices that will reduce or eliminate the mortality of captured animals – the appropriate setting of traps and selection of weather conditions. Also collecting pellets, one should bear in mind the limitations of this method and the differences between the spring-summer and autumn-winter material. The determination of the condition of the habitat may be based on the percentage of deciduous trees, density of trees and the appearance of the undergrowth.

Primary glia cells from bank vole propagate multiple rodent-adapted scrapie prions

Since the beginning prion research has been largely dependent on animal models for deciphering the disease, drug development or prion detection and quantification. Thereby, ethical as well as cost and labour-saving aspects call for alternatives in vitro. Cell models can replace or at least complement animal studies, but their number is still limited and the application usually restricted to certain strains and host species due to often strong transmission barriers. Bank voles promise to be an exception as they or materials prepared from them are uniquely susceptible to prions from various species in vivo, in vitro and in cell-free applications. Here we present a mainly astrocyte-based primary glia cell assay from bank vole, which is infectible with scrapie strains from bank vole, mouse and hamster. Stable propagation of bank vole-adapted RML, murine 22L and RML, and hamster 263K scrapie is detectable from 20 or 30 days post exposure onwards. Thereby, the infected bank vole glia cells show similar or even faster prion propagation than likewise infected glia cells of the corresponding murine or hamster hosts. We propose that our bank vole glia cell assay could be a versatile tool for studying and comparing multiple prion strains with different species backgrounds combined in one cell assay.

Evolution of an increased performance under acute challenge does not exacerbate vulnerability to chronic stress

An adequate stress response plays a vital role in coping with challenges. However, if selection for improved coping with an acute challenge affects the entire stress response system, susceptibility to adverse effects of chronic stressors can be deepened. Here, we used bank voles from lines selected for high swim-induced aerobic metabolism (A) and unselected control (C), and asked if the selection affected sensitivity to chronic mild stress (CMS). The voles were first habituated to daily weighing and feces collection for three weeks, and then for two weeks were exposed to CMS or remained undisturbed. The habituation itself resulted in an increased swim-induced oxygen consumption in both line types, and a decreased body mass. The CMS treatment caused reduction of food consumption in the second week of the experiment, and, in males, a decline in the metabolic rate. Paradoxically, fecal corticosterone metabolites decreased in the CMS-treated group. The response to CMS did not differ between the line types. Thus, the selection for increased performance was not traded off by increased vulnerability to chronic stress. The counter-intuitive results may even lead to a speculation that bank voles—and perhaps also other animals—prefer experiencing unpredictable, unpleasant stressors over the monotony of standard laboratory housing.

Sperm Motility in Bank (Clethrionomys glareolus) and Northern Red-backed Voles (Cl. rutilus) Exposed to Industrial Pollution

Sperm Motility in Bank (Clethrionomys glareolus) and Northern Red-backed Voles (Cl. rutilus) Exposed to Industrial Pollution

Rodent fertility in commercial orchards in relation to body mass and body condition

Although rodents are recognized as pests, they are still an important part of agricultural ecosystems. In 2018–2020, we snap-trapped small mammals in Lithuania in 18 commercial orchards (apple and plum orchards, currant and raspberry plantations) and in adjacent control habitats. We aimed to discover whether the litter size of the six most abundant rodent species depended on season, on female body mass and/or on fitness. Litter size in common and root voles was smaller in habitats with a higher intensity of agricultural practices. Compared to summer, observed litter size in autumn significantly decreased in common voles (from 5.6 to 4.8) and yellow-necked mice (from 5.8 to 4.6). In autumn, litter size and female body mass was positively correlated in all rodent species, while in summer this was characteristic to root voles (r = 0.67, p < 0.05, 45% of variation of the litter size explained) and yellow-necked mice (r = 0.53, p < 0.005, 27% respectively) only. Female body condition index and litter size correlations were weak. Potential litter size exceeded the observed rate and breeding failures were observed in all species, with the highest percentage in root, bank and common voles.