Bank Voles Research Articles

Seasonal shifts and land-use impact: unveiling the gut microbiomes of bank voles (Myodes glareolus) and common voles (Microtus arvalis).

Gut microbial diversity influences the health and vitality of the host, yet it is itself affected by internal and external factors, including land-use. The impact of land-use practices on wild rodents' gut microbiomes remains understudied, despite their abundance and potential as reservoirs for zoonotic pathogens. We examined the bacterial and fungal gut microbiomes of bank voles (Myodes glareolus) and common voles (Microtus arvalis) across grassland and forest habitats with varying land-use intensities and types. We collected rodents seasonally and used 16S rRNA and ITS amplicon sequencing for microbe identification. We found significant differences in alpha and beta diversities between the species, with M. arvalis exhibiting higher diversity. Seasonality emerged as a prominent factor influencing microbial diversity, with significant variations between sampling months. While land-use affects the gut microbiome, its impact is subordinate to seasonal variations. Differential abundance analysis underscores the dynamic nature of microbial composition, with seasonal changes playing a predominant role. Overall, our findings highlight the significant influence of seasonality on gut microbiome diversity and composition in wild rodents, reflecting dietary shifts associated with seasonal changes. Understanding the interplay between environmental factors and microbial communities in wild rodents enahnces our knowledge of ecosystem health and resilience, warranting further investigation.

Insights into tail-belting by wild mice encourages fresh perspectives on physiological mechanisms that safeguard mammal tissues from freezing

We investigated tail-belting (TB), the newly-discovered freeze avoidance behavior among wild rodents. When temperatures dropped to -6 °C, wild mice (Apodemus agrarius and Apodemus flavicollis) were observed curling their tails inward and positioning it on the back. A literature search suggested TB had never been documented, presumably because rodents, especially in the laboratory, are seldomly assayed under cold stress. Due to the infrequent occurrence of the behavior, we used infrared and thermal cameras to confirm observations. We also collected tail-skin samples to investigate whether any physiological mechanisms might co-occur with TB. If such mechanisms were found, they could inform wider debate involving freeze protection among mammals, and could potentially lead to understanding mammal susceptibility or resilience to sudden temperature changes such as those associated with climate change. Lastly, we scored behaviors by bank voles (Myodes glareolus) which unexpectedly visited chambers. Across four winters, we observed TB in both Apodemus species during subzero conditions, but bank voles never performed the behavior. We also confirmed that TB occurs as an adaptive reflex which warms the tail. From tissue samples, we found that free amino acids, peptides, and glycoproteins were significantly higher during cold-stress. Thus, TB may have been accompanied by the expression of cold-protective proteins which ostensibly enable the peripheral body parts of mammals to survive temperatures well below 0 °C. These findings should inspire new dialogue regarding the role of lipids in tissues of peripheral organs in mammals. By extension, our findings may lead to the discovery of a putative cryoprotection mechanism among mammals.

Aonchotheca annulosa and Aonchotheca murissylvatici, which is which? A reappraisal of the gastrointestinal Aonchotheca (Nematoda: Capillariidae) species common in wood mice and bank voles.

Aonchotheca annulosa and Aonchotheca murissylvatici, which is which? A reappraisal of the gastrointestinal Aonchotheca (Nematoda: Capillariidae) species common in wood mice and bank voles.

Bank vole genomics links determinate and indeterminate growth of teeth

BackgroundContinuously growing teeth are an important innovation in mammalian evolution, yet genetic regulation of continuous growth by stem cells remains incompletely understood. Dental stem cells responsible for tooth crown growth are lost at the onset of tooth root formation. Genetic signaling that initiates this loss is difficult to study with the ever-growing incisor and rooted molars of mice, the most common mammalian dental model species, because signals for root formation overlap with signals that pattern tooth size and shape (i.e., cusp patterns). Bank and prairie voles (Cricetidae, Rodentia, Glires) have evolved rooted and unrooted molars while retaining similar size and shape, providing alternative models for studying roots.ResultsWe assembled a de novo genome of Myodes glareolus, a vole with high-crowned, rooted molars, and performed genomic and transcriptomic analyses in a broad phylogenetic context of Glires (rodents and lagomorphs) to assess differential selection and evolution in tooth forming genes. Bulk transcriptomics comparisons of embryonic molar development between bank voles and mice demonstrated overall conservation of gene expression levels, with species-specific differences corresponding to the accelerated and more extensive patterning of the vole molar. We leverage convergent evolution of unrooted molars across the clade to examine changes that may underlie the evolution of unrooted molars. We identified 15 dental genes with changing synteny relationships and six dental genes undergoing positive selection across Glires, two of which were undergoing positive selection in species with unrooted molars, Dspp and Aqp1. Decreased expression of both genes in prairie voles with unrooted molars compared to bank voles supports the presence of positive selection and may underlie differences in root formation.ConclusionsOur results support ongoing evolution of dental genes across Glires and identify candidate genes for mechanistic studies of root formation. Comparative research using the bank vole as a model species can reveal the complex evolutionary background of convergent evolution for ever-growing molars.

Effect of Pregnancy on Mercury Concentration in the Body of Free-living Small Rodents.

Relatively little information exists on the effects of mercury on terrestrial wildlife populations. We analyzed 38 free-living small rodent females (Myodes glareolus, Microtus agrestris, and Apodemus flavicolis), of which 11 were pregnant, for total mercury concentrations in combined liver and kidney samples. Using a single-purpose atomic absorption spectrometer for mercury determination, the measured mercury values ranged from 0.006 to 0.079 mg/kg. Pregnant females had significantly (P<0.041) higher mercury levels in liver and kidney than did nonpregnant females. Our results suggest that during mercury biomonitoring studies it is necessary to consider the pregnancy of the analyzed animals.

Assessment of genetic diversity, tissue tropism, and antigenic properties of Grimsö betacoronavirus in Swedish bank voles (Clethrionomys glareolus)

Zoonotic coronaviruses can transmit over species barriers and infect humans. To understand the zoonotic potential of a betacoronavirus, Grimsö virus (GRIV), we investigated the geographic distribution and tissue tropism of GRIV in Swedish bank voles (Clethrionomys glareolus), and the antigenicity of the nucleocapsid (N) protein. We screened the lung tissues from animals collected in the southern Sweden by RT-PCR with primers targeting the spike gene. Seven out of 74 animals were found to be positive. They are genetically close to GRIV from Grimsö, central Sweden. Positive rodents were studied for the tissue distribution of GRIV and GRIV RNA was mainly found in the respiratory tract. After three attempts of virus isolation were failed, we successfully established a Vero E6 cell line that stably expressed GRIV N protein, which has no cross-reactivity with patient serum containing antibodies against SARS-CoV-2, or with MERS-CoV. However, a low level of cross-reactivity to common cold coronaviruses was found, likely HCoV-OC43 or HCoV-HKU1, probably due to shared linear epitopes. With the high prevalence and the suggested respiratory transmission route, GRIV may have a high potential for spillover and cross-species transmission, and future serological screening of GRIV infections in domestic animals or humans will be needed.

Wildlife as Reservoirs of Encephalitozoon Cuniculi and Encephalitozoon Hellem and Molecular Genotyping of Encephalitozoon spp. in Small Mammals in the Czech Republic.

Parasites of genus Encephalitozoon are well known pathogens of domestic animals however less attention was paid to its spread among wildlife that can play an important role of reservoir of infection. The aim of the study was to conduct molecular detection and genotype characterization of Encephalitozoon spp. in wild small mammals trapped in localities both near to and at a large distance from residential areas. In total, 300 wild small mammals (274 Rodentia and 26 Eulipotyphla) were trapped in 41 localities of the Czech Republic and tested by nested PCR for Encephalitozoon spp. The DNA of Encephalitozoon spp. was proved in tissues (brain or liver) of 11% (32/300) of animals. There was a statistically significant difference (p < 0.001) in positivity among animal species with the most infected species Micromys minutus (50%, 4/8) and Myodes glareolus (17%, 9/53). There was also statistically significant difference (p < 0.001) between localities with the higher positivity (29%, 12/42) in localities near to residential areas, compared to localities with a large distance from residential areas (8%, 20/258). Sex and age of wild small mammals did not have effect on their positivity. Genotyping analysis revealed E. cuniculi genotype II in 22 samples and E. hellem genotype 1A in one sample. This study brings new information on the molecular characterization of Encephalitozoon spp. isolated from wild small mammals trapped in two different areas (localities in near to residential areas and localities with a large distance from residential areas).

Fur microbiome as a putative source of symbiotic bacteria in sucking lice

Symbiosis between insects and bacteria has been established countless times. While it is well known that the symbionts originated from a variety of different bacterial taxa, it is usually difficult to determine their environmental source and a route of their acquisition by the host. In this study, we address this question using a model of Neisseriaceae symbionts in rodent lice. These bacteria established their symbiosis independently with different louse taxa (Polyplax, Hoplopleura, Neohaematopinus), most likely from the same environmental source. We first applied amplicon analysis to screen for candidate source bacterium in the louse environment. Since lice are permanent ectoparasites, often specific to the particular host, we screened various microbiomes associated with three rodent species (Microtus arvalis, Clethrionomys glareolus, and Apodemus flavicollis). The analyzed samples included fur, skin, spleen, and other ectoparasites sampled from these rodents. The fur microbiome data revealed a Neisseriaceae bacterium, closely related to the known louse symbionts. The draft genomes of the environmental Neisseriaceae, assembled from all three rodent hosts, converged to a remarkably small size of approximately 1.4 Mbp, being even smaller than the genomes of the related symbionts. Our results suggest that the rodent fur microbiome can serve as a source for independent establishment of bacterial symbiosis in associated louse species. We further propose a hypothetical scenario of the genome evolution during the transition of a free-living bacterium to the member of the rodent fur-associated microbiome and subsequently to the facultative and obligate louse symbionts.

Effect of chemical pollution on the fertility of male rodents from natural populations: сomparing the response of sperm morphology, motility, and concentration

The results of studies of epididymal spermatozoa of three species of rodents (bank vole Clethrionomys glareolus, northern red-backed vole Cl. rutilus, and herb field mouse Sylvaemus uralensis) living under long-term exposure to atmospheric emissions from two large copper smelters in the Middle Urals are summarized (Middle Ural and Kirovgrad copper smelters). The impact of pollution (including at the individual level on the accumulation of Cu, Zn, Pb, and Cd in the liver) was assessed for indicators characterizing the quality of sperm from different aspects: morphology (proportion of cells with head and tail defects), motility (proportion of motile cells, velocity, and straightness of movement) and concentration. Sperm motility responds to pollution: in impact zones, the proportion of motile cells and their velocity were lower than in background zones. The occurrence of abnormal cells and sperm concentration were not statistically significantly different between impact and background zones. The reaction of sperm to chemical pollution is species-specific: voles react more strongly than the herb field mouse. The consistency of changes in sperm parameters (in the direction of their deterioration) in response to increased pollution was found only in the bank vole. Effect sizes for sperm parameters are much smaller compared to those for liver Cd accumulation and animal abundance. In general, the reaction of sperm to pollution turned out to be weak, none of the studied indicators can be a reliable marker of industrial pollution.

Interplay between vertebrate adaptive immunity and bacterial infectivity genes: Bank vole MHC versus Borrelia afzelii OspC.

Coevolution of parasites with their hosts may lead to balancing selection on genes involved in determining the specificity of host-parasite interactions, but examples of such specific interactions in wild vertebrates are scarce. Here, we investigated whether the polymorphic outer surface protein C (OspC), used by the Lyme disease agent, Borrelia afzelii, to manipulate vertebrate host innate immunity, interacts with polymorphic major histocompatibility genes (MHC), while concurrently eliciting a strong antibody response, in one of its main hosts in Europe, the bank vole. We found signals of balancing selection acting on OspC, resulting in little differentiation in OspC variant frequencies between years. Neither MHC alleles nor their inferred functional groupings (supertypes) significantly predicted the specificity of infection with strains carrying different OspC variants. However, we found that MHC alleles, but not supertypes, significantly predicted the level of IgG antibodies against two common OspC variants among seropositive individuals. Our results thus indicate that MHC alleles differ in their ability to induce antibody responses against specific OspC variants, which may contribute to selection of OspC polymorphism by the vole immune system.

The molecular determinants of a universal prion acceptor.

In prion diseases, the species barrier limits the transmission of prions from one species to another. However, cross-species prion transmission is remarkably efficient in bank voles, and this phenomenon is mediated by the bank vole prion protein (BVPrP). The molecular determinants of BVPrP's ability to function as a universal prion acceptor remain incompletely defined. Building on our finding that cultured cells expressing BVPrP can replicate both mouse and hamster prion strains, we systematically identified key residues in BVPrP that permit cross-species prion replication. We found that residues N155 and N170 of BVPrP, which are absent in mouse PrP but present in hamster PrP, are critical for cross-species prion replication. Additionally, BVPrP residues V112, I139, and M205, which are absent in hamster PrP but present in mouse PrP, are also required to enable replication of both mouse and hamster prions. Unexpectedly, we found that residues E227 and S230 near the C-terminus of BVPrP severely restrict prion accumulation following cross-species prion challenge, suggesting that they may have evolved to counteract the inherent propensity of BVPrP to misfold. PrP variants with an enhanced ability to replicate both mouse and hamster prions displayed accelerated spontaneous aggregation kinetics in vitro. These findings suggest that BVPrP's unusual properties are governed by a key set of amino acids and that the enhanced misfolding propensity of BVPrP may enable cross-species prion replication.

Impact of coarse woody debris on habitat use of two sympatric rodent species in the temperate Białowieża Forest

Abstract Importance of coarse woody debris (CWD) in habitat use of small mammals has not been thoroughly explored, especially for European species. Moreover, despite the growing awareness about the need for protecting CWD resources in forests, their amount is usually quantified with regard to current or desired volume. The area of forest floor covered by CWD is rarely considered, despite its potential importance for habitat use of small mammals. Over a period of three summer seasons (4800 trap-nights), we examined the populations of yellow-necked mouse Apodemus flavicollis and bank vole Clethrionomys glareolus through capture-mark-recapture trapping at three 1-hectare study sites, including both managed forests and a nature reserve in Białowieża Forest, Poland. We applied generalized linear mixed models on a sample of 236 adult individuals of yellow-necked mouse and 173 adult individuals of bank vole to establish that the access to CWD is a significant aspect of their habitat use. Our results suggest that both species prefer a certain minimum amount of CWD. After accounting for different aspects of forest undergrowth, we established that bank vole more frequently used areas with a relatively large amount of CWD (threshold of 0.75 m$^{3}$ CWD per 100 m$^{2}$), together with a propensity to choose areas with debris in the later stages of decay. Yellow-necked mouse was found more frequently in areas with at least 1.5 m$^{2}$ of CWD. We suggest that manipulating CWD distribution, or possibly vegetation characteristics, could be a strategy for managing the abundance and distribution of rodents in forest stands—especially when both CWD volume and coverage are taken into account.

A behavioral syndrome of competitiveness in a non-social rodent

Animals compete for limited resources such as food, mating partners, and territory. The outcome of this intraspecific competition should be determined by individual variation in behavioral traits, such as aggressiveness and dominance status. Consistent among-individual differences in behavior likely contribute to competitiveness and predispose individuals to acquire specific dominance ranks during parts of their adult life. Nevertheless, how dominance rank is correlated with animal personality traits remains largely unclear. In a first step towards better understanding these functional links, we studied trait integration into behavioral syndromes, using 26 captive male bank voles (Myodes glareolus). We repeatedly assessed boldness in an emergence test, exploration in an open-field test, aggressiveness in staged dyadic encounters, and the among-individual correlations between these behaviors. We further related these personality traits to dominance rank, from quantifying urine marking value (UMV), as marking in bank voles is related to dominance rank. We found repeatable variations in boldness, exploration, aggressiveness, and UMV, which were correlated at the among-individual level. Aggressiveness tended to be negatively correlated with body condition, a proxy for fitness. Thus, key personality traits and social rank are functionally integrated into a behavioral syndrome of intraspecific competitiveness. By joining social and non-social aspects of personality, our findings contribute to the ecological validation of personality traits and suggest how they contribute to higher-order component traits, such as dominance which directly affect fitness components.

Foraging Habitat Availability and the Non-Fish Diet Composition of the Grey Heron (Ardea cinerea) at Two Spatial Scales.

Habitat structure on foraging ground is one of the crucial factors determining diet diversity in colonially breeding avian predators. Quantifying the habitat and diet composition at different spatial scales (regional and local inter-colonial) can help provide understanding of the drivers of diet composition. In this study, we examined the composition of the non-fish diet of an opportunistic predator, the Grey Heron (Ardea cinerea), based on pellets. We compared pellets from 21 colonies in two different regions of Poland that differing in composition of foraging habitats. Multivariate statistical techniques were used to analyze the relationship between diet and habitat compositions in a 20 km radius around these colonies. Significant inter-regional and inter-colony differences in Grey Heron diet and habitat composition were detected in foraging areas. However, some prey were present in the diet only from one of the regions. Around the heronries with a predominance of farmland habitats, the European water vole (Arvicola amphibius) and terrestrial invertebrates were present in relatively low frequencies, and the striped field mouse (Apodemus agrarius) was present in high frequencies. Voles (Microtus sp.) were more frequent in colonies with prevalence of non-irrigated arable land around the colony, in contrast to the bank vole (Myodes glareolus), which was less common in heronries with a higher contribution of this habitat type. Remains of aquatic invertebrates were less abundant in colonies surrounded by extensive forests. The results of our research indicate the opportunistic character of the non-fish part of the diet of the Grey Heron adapted to the local foraging habitat and prey availability.

Association between Outlying Values in Body Condition Indices in Small Mammals and Their Habitats

Habitat type and habitat change are very important factors in the body condition of small mammals that inhabit them. The response can be positive, increasing, or the opposite, decreasing body condition. We analyzed outliers of the body condition indices (BCIs) of 12 species trapped in nine different habitats during 1980–2023 in Lithuania, a mid-latitude country. Mixed and fragmented habitats, as well as commensal habitats, could be considered the least suitable for small mammals, based on the highest proportions of underfit and low proportions of best-fit individuals. On the contrary, meadows and disturbed habitats (landfills and cormorant colonies) had the highest proportions of best-fit individuals, while the proportion of under-fit individuals was much lower than expected. We found outliers in the BCI in all species, except for the under-fit harvest mice (Micromys minutus), and in all habitats, though not numerous. The presence of the highest BCI in yellow-necked mice (Apodemus flavicollis) and bank voles (Clethrionomys glareolus) in the disturbed habitats studied and in house mice (Mus musculus) in commensal habitats may be related to the resources provided by these habitats. Our results demonstrate the feasibility of using retrospective small mammal morphometric data to analyze their relationship with habitat.

Habitat and Body Condition of Small Mammals in a Country at Mid-Latitude

The relationship between the body condition of different small mammal species and the habitat they occupy is poorly analyzed. We analyzed the body condition index, BCI, of 18 small mammal species trapped in forest, shrub, wetland, meadow, riparian, mixed and fragmented, disturbed, agricultural, and commensal habitats of Lithuania during the span of 1980–2023. The composition of small mammal communities was habitat-dependent, being richest in meadows, with eighteen species, and poorest in riparian habitats, with nine species. A significant variation in the BCI with respect to habitat was observed in eight small mammal species (Sorex araneus, S. minutus, Apodemus agrarius, A. flavicollis, Clethrionomys glareolus, Alexandromys oeconomus, Microtus agrestis, and M. arvalis). The highest average BCI for most of these species was found in disturbed habitats, with S. minutus and M. arvalis showing the highest BCI in agricultural habitats. The lowest average BCI for most species was found in mixed habitats, while C. glareolus and M. arvalis exhibited the lowest BCI in shrub habitats. In general, species dominating certain habitats did not have the highest BCI. This is the first multi-species, multi-habitat study of body condition in small mammals at mid-latitudes.

Visual analysis of hot spots and trends in research of meteorology and hemorrhagic fever with renal syndrome: a bibliometric analysis based on CiteSpace and VOSviewer

Objective: We here displayed the global research trends of meteorology and hemorrhagic fever with renal syndrome (HFRS) as a visual knowledge map by using bibliometrics and revealed the research directions, hotspots, trends, and frontiers in this field.Methods: Using Web of Science core collection as the data source and with CiteSpace and VOSviewer software, we collected and analyzed the annual number of papers, cooperative relationships (countries, institutions, authors, etc.), citations (literature citation, literature co-citation, literature publication, etc.), keywords (emergence, clustering, etc.) of meteorology, and HFRS-related research data for the past 30 years, and drew a visual map.Results: In total, this study included 313 papers investigating the relationship between meteorology and HFRS. The first paper was published in 1992. Globally, United States had the largest number of publications in this field, and the Chinese Center for Disease Control and Prevention was the most influential institution conducting related research (20 articles published, and the mediation centrality was 0.24). Several small author cooperation clusters were formed; however, the number of papers published by the same scholar and the co-citation frequency were low. Cazelles Bernard (7 articles) published the highest number of articles in this field, and Gubler DJ was the author with the most co-citations (55 times). The most frequently cited journal was Emerging Infectious Diseases. In this field, the top three high-frequency keywords were “hemorrhagic fever,” “transmission,” and “temperature.” According to keyword cluster analysis, the top three themes were dengue, dechlorane plus, and bank voles. The timeline spectrum exhibited that dengue clustering had a good temporal continuity. The trend analysis of emergent words revealed that the research on “temperature,” “meteorological factors” and “Puumala hantavirus” has gradually appeared in recent years.Conclusion: This study represents the first comprehensive exploration of global trends, hotspots, frontiers, and developments in the relationship between meteorology and HFRS, utilizing CiteSpace and VOSviewer software. The findings of this study are crucial for elucidating the influence of climate change on disease transmission patterns and offering novel insights for forthcoming epidemiological research and public health interventions.

Interrelation of the spatial and genetic structure of tick-borne encephalitis virus, its reservoir host (Myodes glareolus), and its vector (Ixodes ricinus) in a natural focus area.

Tick-borne encephalitis (TBE) virus is considered the medically most important arthropod-borne virus in Europe. Although TBE is endemic throughout central Europe, ticks and rodents determine its maintenance in small, difficult-to-assess, natural foci. We investigated the interrelation between the population genetics of the main TBE virus (TBEV) vector tick (Ixodes ricinus), the most important reservoir host (Myodes glareolus, syn. Clethrionomys glareolus), and TBEV. Rodents and ticks were sampled on 15 sites within an exploratory study area, which has been screened regularly for TBEV occurrence in ticks for more than 10 years. On all 15 sites, ticks and bank voles were sampled, screened for TBEV presence via serology and RT-PCR, and genetically examined. Moreover, TBEV isolates derived from these analyses were sequenced. In long-term TBEV foci bank vole populations show extraordinary genetic constitutions, leading to a particular population structure, whereas ticks revealed a panmictic genetic structure overall sampling sites. Landscape genetics and habitat connectivity modeling (analysis of isolation by resistance) showed no landscape-related barriers explaining the genetic structure of the bank vole populations. The results suggest that bank voles do not simply serve as TBEV reservoirs, but their genetic composition appears to have a significant influence on establishing and maintaining long-term natural TBEV foci, whereas the genetic structure of TBEV's main vector I. ricinus does not play an important role in the sustainability of long-term TBEV foci. A thorough investigation of how and to which extent TBEV and M. glareolus genetics are associated is needed to further unravel the underlying mechanisms.

Convergent generation of atypical prions in knockin mouse models of genetic prion disease.

Most cases of human prion disease arise due to spontaneous misfolding of WT or mutant prion protein, yet recapitulating this event in animal models has proven challenging. It remains unclear whether spontaneous prion generation can occur within the mouse lifespan in the absence of protein overexpression and how disease-causing mutations affect prion strain properties. To address these issues, we generated knockin mice that express the misfolding-prone bank vole prion protein (BVPrP). While mice expressing WT BVPrP (I109 variant) remained free from neurological disease, a subset of mice expressing BVPrP with mutations (D178N or E200K) causing genetic prion disease developed progressive neurological illness. Brains from spontaneously ill knockin mice contained prion disease-specific neuropathological changes as well as atypical protease-resistant BVPrP. Moreover, brain extracts from spontaneously ill D178N- or E200K-mutant BVPrP-knockin mice exhibited prion seeding activity and transmitted disease to mice expressing WT BVPrP. Surprisingly, the properties of the D178N- and E200K-mutant prions appeared identical before and after transmission, suggesting that both mutations guide the formation of a similar atypical prion strain. These findings imply that knockin mice expressing mutant BVPrP spontaneously develop a bona fide prion disease and that mutations causing prion diseases may share a uniform initial mechanism of action.

Trophic fate and biomagnification of organic micropollutants from staple food to a specialized predator

The environmental burden of organic micropollutants has been shown in aquatic ecosystems, while trophic fate of many compounds in terrestrial food chains remains highly elusive. We therefore studied concentrations of 108 organic micropollutants in a common European mammal, the bank vole (Clethrionomys glareolus), and 82 of the compounds in a specialized predator, Tengmalm's owl (Aegolius funereus) relying to >90 % on voles as its prey. We studied compounds in whole voles (n = 19), pools of 4–8 bank voles (npools = 4), owl blood (n = 10) and in owl eggs (n = 10) in two regions in Sweden. For comparison, we also included previously published data on 23 PFAS (per- and polyfluoroalkyl substances) in bank vole liver (npools = 4) from the same regions. In voles, concentrations of the organic micropollutants caffeine (maxIndividual 220 ng/g ww) and DEET (N,N-diethyl-m-toluamide) (maxPool 150 ng/g ww) were 2–200 times higher in voles relative to owl blood and eggs. Conversely, concentrations of nicotine, oxazepam, salicylic acid, and tributyl citrate acetate were 1.3–440 times higher in owls. Several PFAS showed biomagnification in owls as revealed by maximum biomagnification factors (BMFs); PFNA (perfluorononanoate) BMF = 5.6, PFTeDA (perfluorotetradecanoic acid) BMF = 5.9, and PFOS (perfluorooctane sulfonate) BMF = 6.1. Concentrations of organic micropollutants, alongside calculated BMFs, and Tengmalm's owl's heavy reliance on bank vole as staple food, suggest, despite small sample size and potential spatio-temporal mismatch, accumulation of PFAS (especially PFNA, PFTeDA, and PFOS) in owls and biomagnification along the food chain. Concentrations of PFAS in owl eggs (e.g., 21 ng/g ww PFOS) highlight the likely pivotal role of maternal transfer in contaminant exposure for avian embryos. These concentrations are also of concern considering that certain predators frequently consume owl eggs, potentially leading to additional biomagnification of PFAS with yet undetermined consequences for ecosystem health.