Bank Voles Research Articles

Bartonella spp. in Small Mammals and Their Fleas in Differently Structured Habitats From Germany.

Most Bartonella spp. are transmitted by fleas and harbored by small mammals which serve as reservoirs. However, little is known about the composition of fleas and their Bartonella spp. from small mammals in Central Europe. Therefore, the aims of this study were to investigate flea communities on small mammals from three differently structured sites (urban, sylvatic, renatured) in Germany as well as the prevalence of Bartonella spp. in small mammals and their parasitizing fleas. In total, 623 small mammals belonging to 10 different species (the majority were Myodes glareolus and Apodemus flavicollis) were available. Fleas were removed from the small mammals' fur, morphologically identified and DNA was extracted. To detect Bartonella spp., two conventional PCRs targeting the gltA gene and the 16S−23S rRNA intergenic spacer were carried out followed by sequencing. Obtained sequences were compared to those in GenBank. In total, 1,156 fleas were collected from 456 small mammals. Altogether, 12 different flea species (the majority were Ctenophthalmus agyrtes, Nosopsyllus fasciatus, and Megabothris turbidus) were detected. At the urban site mostly Leptopsylla segnis and N. fasciatus were collected which may be vectors of zoonotic pathogens to companion animals. The overall prevalence for Bartonella in small mammals was 43.3% and in fleas 49.1%. Five different Bartonella spp. were detected in small mammals namely B. grahamii, B. taylorii, B. doshiae, Bartonella sp. N40 and uncultured Bartonella sp. whereas in fleas four Bartonella spp. were found which were with the exception of B. doshiae identical to the Bartonella species detected in their small mammal hosts. While B. grahamii was the only zoonotic Bartonella sp. most Bartonella strains found in fleas and small mammals belonged to uncultured Bartonella spp. with unknown zoonotic potential. This study showed a high diversity of flea species on small mammals from Germany. Further, high prevalence rates of Bartonella species were detected both in fleas and in their mammalian hosts. Several different Bartonella species with a high genetic variability were discovered. Especially at the urban study sites, this may pose a risk for Bartonella transmission to companion animals and humans.

Host-Dependent Clustering of Campylobacter Strains From Small Mammals in Finland.

Small mammals are known to carry Campylobacter spp.; however, little is known about the genotypes and their role in human infections. We studied intestinal content from small wild mammals collected in their natural habitats in Finland in 2010–2017, and in close proximity to 40 pig or cattle farms in 2017. The animals were trapped using traditional Finnish metal snap traps. Campylobacter spp. were isolated from the intestinal content using direct plating on mCCDA. A total of 19% of the captured wild animals (n = 577) and 41% of the pooled farm samples (n = 227) were positive for C. jejuni, which was the only Campylobacter species identified. The highest prevalence occurred in yellow-necked mice (Apodemus flavicollis) and bank voles (Myodes glareolus) which carried Campylobacter spp. in 66.3 and 63.9% of the farm samples and 41.5 and 24.4% of individual animals trapped from natural habitats, respectively. Interestingly, all house mouse (Mus musculus) and shrew (Sorex spp.) samples were negative for Campylobacter spp. C. jejuni isolates (n = 145) were further characterized by whole-genome sequencing. Core genome multilocus sequence typing (cgMLST) clustering showed that mouse and vole strains were separated from the rest of the C. jejuni population (636 and 671 allelic differences, 94 and 99% of core loci, respectively). Very little or no alleles were shared with C. jejuni genomes described earlier from livestock or human isolates. FastANI results further indicated that C. jejuni strains from voles are likely to represent a new previously undescribed species or subspecies of Campylobacter. Core-genome phylogeny showed that there was no difference between isolates originating from the farm and wild captured animals. Instead, the phylogeny followed the host species-association. There was some evidence (one strain each) of livestock-associated C. jejuni occurring in a farm-caught A. flavicollis and a brown rat (Rattus norvegicus), indicating that although small mammals may not be the original reservoir of Campylobacter colonizing livestock, they may sporadically carry C. jejuni strains occurring mainly in livestock and be associated with disease in humans.

Bilberry seed production explains spatiotemporal synchronicity in bank vole population fluctuations in Norway

AbstractPopulation fluctuations of small rodents are often synchronized over larger areas (>100 km) than what could be explained by dispersal, suggesting that the synchronizing factor is weather‐related and possibly mediated through changes in food quality. Because bank vole (Myodes glareolus) populations usually peak 1 year after peaks in reproduction of the staple winter food plant bilberry (Vaccinium myrtillus), we tested for a possible link between food and spatial synchrony by comparing the synchrony in bank vole population indices and bilberry seed production indices between three study areas across about 20,000 km2 in South Norway during a four decade period (1979–2019). There were subperiods of spatial synchrony and asynchrony between the study areas in the fluctuations of bank vole numbers and bilberry seed production, with the latter part of the study period displaying more pronounced synchrony than the first and middle part. However, with a few marked exceptions, when vole fluctuations were spatially out of phase across study areas so was bilberry seed production. Thus, we conclude that bilberry seed production to a large extent explained the spatiotemporal synchronicity in bank vole population fluctuations. Although bilberry seed production seems to be a causal driver of vole fluctuations, it remains to be seen to what extent the chemical composition of bilberry plants influences vole performance. Finally, certain weather factors may still influence voles directly, or indirectly by triggering bilberry seed production.

Low levels of faecal cortisol in bank voles (Myodes glareolus) in response to live-trapping

Small mammal trapping is a commonly taught field technique in ecology and population biology. However, there are still open questions regarding the extent to which trapping affects the welfare of small animals. This study investigated faecal cortisol as a non-invasive measurement of the physiological stress response of bank voles (Myodes glareolus) to live-trapping. Faecal cortisol concentrations were similar between samples collected from trapped and non-trapped voles, but were negatively correlated with capture duration. This result may suggest that any physiological stress response was short-lasting and the animals habituated to the trap. As such, effects on faecal cortisol were not apparent as mean faecal cortisol concentration was determined from multiple collected faeces. Future work should focus on characterising the potential stress response to trapping with greater temporal resolution.

Assessment of mouse rodents’ dose from the CHNPP contaminated territories

The main feature of the nearest 5-km zone of the Chernobyl nuclear power plant is the maximum concentration of fuel fallouts due to the accident in 1986. It is a unique testing ground for radiobiological research in the natural habitat of animals. At present, the background radiation level in the 5-km zone of the Chernobyl nuclear power plant fluctuates from 0.1 to 20 μSv/h. Besides, electrons from the decay of 90Sr and 137Cs add a significant contribution to the radiation background. Even though a large amount of experimental data on dose loads on the fauna of affected areas has been accumulated to date, the results obtained do not give an unambiguous idea of the dose dependences of radiobiological effects in natural ecosystems. In this work, we studied the total dose of irradiation of two murine rodents species: the bank vole (Clethrionomys glareolus) and the yellow-necked mouse (Apodemus flavicollis), living in territories of different levels of pollution near the destroyed power unit 4 of the Chernobyl nuclear power plant. We have assessed the density of radioactive contamination of the territory and study the isotopic composition of the fallout. Soil samples were taken to a depth of 30 cm, considering the depth of burrowing of mouse-like burrows is 10-15 cm. The 90Sr, 90Y, and 137Cs concentrations were measured using β- and γ-spectrometric methods for the selected soil samples. The 90Sr, 90Y, and 137Cs βactivity spectra were measured using a developed scintillation beta-spectrometer with a thin entrance window. Soil samples' gamma spectrometric studies were carried out using an anti-Compton device with an HPGe detector. The method for processing complex Xray and gamma-spectra in the energy range of 10-100 keV is developed. It takes into account the complexity of describing X-ray lines and providing a processing error of ≤1%. We calculated the murine rodents' radiation doses using the obtained data on the concentration of 90Sr, 90Y, and 137Cs activities in soil samples and animal bodies. The doses were calculated due to external irradiation with γ-quanta and electrons and internal irradiation with 137Cs and 90Sr electrons. For the first time, we obtained data on external electrons' contribution to the total dose of irradiation of murine rodents living in the contaminated territories of the 5-km zone of the Chernobyl nuclear power plant. Doses of internal irradiation and external γ-quanta are in good agreement with the data obtained for these territories earlier. It was found that the radiation dose is formed mainly due to external electrons for most rodents. Since many studies, including genetic and biochemical ones, are tied to the radiation dose, the correct account of the contribution of electrons to the radiation dose is, in many cases, critical.

Оценка радиоэкологической обстановки на территориях аварийного чернобыльского следа в России (1986-2020)

The current environmental situation in areas located in the “Chernobyl footprint” in Russia is con-sidered in the paper. Radiation contamination in different parts of the “footprint” varies from the maximum level in the exclusion zones to the level close to the background in areas with low level of radioactive contamination. Environmental monitoring data and calculated density of soil con-tamination with radionuclides in the vicinities of residential areas in Bryansk, Kaluga, Tula, Orel and Novgorod regions were used as reference data for assessment of radiation dose rates and ecological risks for the reference biological species: the elk (Alces alces), red-backed mouse (Myodes glareolus), the Archangel fir (Pinus sylvestris), brandling (Lumbricus terrestris), the pike (Esox lucius), and the fresh-water soldier (Stratiotes aloides). The integrated contamination index, that is the sum of ratios of registered radionuclides contamination density to the reference levels, was used as the indicator of territory radioecological safety. The calculation was made in accord-ance with the Roshydromet Recommendations R-52.18.853-2016. The highest doses to the biota and ecological risks were registered in 1986. Radiation dose rates to some vertebrates in the most contaminated districts of the Bryansk region in May 1986 exceeded ecologically safe radiation level of 1 mGy/day. Doses to reference biological species inhabited outside exclusion zones within the period of May-December 1986 were lower than the radioecological safety level. After decay of 131I and other short-lived radionuclides 137Cs became the basic contributor to the biota dose. Radiation dose rate to the terrestrials and radio-ecological safety index gradually decreased due to radionuclides physical decay over the period of 1986-2020. Current radiation doses to the terrestrials inhabited the most contaminated districts were, on average, one order below the safe radiation dose to the vertebrates, two orders below the safety radiation level to the Archangel fir and three orders be-low the safety radiation dose to the soil invertebrates. Current radiation dose rates to inhabitants of the lake of Kozhanovskoe, one of the most contaminated areas due to the radioactive fallout, current radiation dose rates to the lake fish were two orders below the safe level, radiation dose rates to algae were three orders below the safety level, however, they still are above the back-ground level. Current indices of integrated contamination in areas of the Chernobyl radioactive “footprint” are inhomogeneous. Current indices of integrated contamination in the majority of contaminates areas are dozens times and the indices in low radiation contaminated areas are hundreds times lower than ecological safety level. The highest indices occur in a number of dis-tricts of Bryansk region but they are lower than ecological safety level, however in some sites in exclusion zones the indices exceed the ecological safety level. These sites are unique natural testing grounds for radio-ecological research and monitoring of the environment and radiation protection development. In this connection it is recommended to continue long term research and development of radiological protection of the environment.

Population Cycles and the Chitty Syndrome

Data are presented on the long-term population dynamics of small mammals (1982–2019) and variation in the body weight and length of the bank vole, a dominant species, in southern taiga forests of the Middle Urals. Spontaneous change in the pattern of dynamics observed in our previous study—transition from regular 3-year cycles to noncyclic regime—provided the possibility to estimate the influence of different factors on the Chitty effect (increase in body size at high population numbers) under different regimes. This effect was clearly manifested in the bank vole population with cyclic dynamics: the average body weight and length of the animals were greater at the phases of population growth and peak than at the trough (low) phase, while the same parameters of voles from the noncyclic regime had intermediate values. The body size of animals depends not so much on population density as on factors determining their physiological status (including reproductive status).

Global dynamics of a stage-structured hantavirus infection model with seasonality

In this paper, we study a time-periodic model, which incorporates seasonality and host stage-structure. This model describes the propagation of Puumala hantavirus within the bank vole population of Clethrionomys glareolus. The basic reproduction number R0 is obtained. By appealing to the theory of monotone dynamical systems and chain transitive sets, we establish a threshold-type result on the global dynamics in terms of R0, that is, the virus-free periodic solution is globally attractive, and the virus dies out if R0 ≤ 1, while there exists a unique positive periodic solution, which is globally attractive, and the virus persists if R0 > 1. Numerical simulations are given to confirm our theoretical results and to show that cleaning environment and controlling the grow of mice population are essential control strategies to reduce hantavirus infection.

Hantavirus-Leptospira coinfections in small mammals from central Germany.

European orthohantaviruses (Puumala orthohantavirus (PUUV); Dobrava-Belgrade orthohantavirus (DOBV), genotype Kurkino; Tula orthohantavirus (TULV)), and Leptospira spp. are small mammal-associated zoonotic pathogens that cause diseases with potentially similar symptoms in humans. We investigated the frequency of Leptospira spp. and hantavirus single and double infections in small mammals from 22 sites in Thuringia, central Germany, during 2017. TULV infections were detected at 18 of 22 sites (mean prevalence 13.8%, 93/674). PUUV infections were detected at four of 22 sites (mean prevalence 1.5%, 7/471), and respective PUUV sequences formed a novel phylogenetic clade, but DOBV infections were not detected at all. Leptospira infections were detected at 21 of 22 sites with the highest overall prevalence in field voles (Microtus agrestis) with 54.5% (6/11) and common voles (Microtus arvalis) with 30.3% (205/676). Leptospira-hantavirus coinfections were found in 6.6% (44/671) of common voles but only in two of 395 bank voles. TULV and Leptospira coinfection probability in common voles was driven by individual (age) and population-level factors. Coinfections seemed to be particularly associated with sites where Leptospira spp. prevalence exceeded 35%. Future investigations should evaluate public health consequences of this strong spatial clustering of coinfections.

Geographic Ecological Analysis of Small Mammals of the Northern Taiga of Western Siberia

The analysis of all data on the number and distribution of small mammals in Western Siberia over the past 120 years has established that 20 out of 28 species recorded in the northern taiga make up their communities. A similar structure of dominance is generally preserved in the small mammal communities of the northern taiga. The main dominant species, northern red-backed vole, Laxmann’s shrew, and the common shrew, predominate almost everywhere. The other six codominant species (Eurasian pygmy shrew and tundra shrew and voles: root vole, common European field vole, European bank vole, and gray red-backed vole) dominate only in certain areas. The remaining 11 species, which are both widely and narrowly distributed, make up a small part of the communities. The increase in the species richness of communities to the east (from 15 to 19 species) is determined by the increase in the number of Siberian species. In general, in the studied area of the northern taiga, the largest contribution to small mammal communities is made by representatives of the Siberian fauna type, with the exception of the western part of the subzone, where European species predominate.

Small mammals of the suburban areas of Warsaw in the diet of the tawny owl Strix aluco

We investigated the composition of small mammals at nine locations in the southwestern suburban zone of Warsaw (central Poland) through the analysis of the pellets of the Tawny owl Strix aluco. In total, we recorded 611 individuals of 15 species of small mammal communities in the diet. Rodents constituted the most numerous mammalian order. Among the most abundant prey we recorded were Myodes glareolus (63 individuals = 10.3% of all mammals), Apodemus agrarius (56 individuals = 9.2%) (173), Apodemus flavicollis (54 individuals = 8.8%), Mus musculus (48 individuals = 7.9%) and Microtus arvalis (44 individuals = 7.2%). We recorded also some species rarely captured by the tawny owl: Nyctalus noctula and Mustela nivalis. Species composition of small mammals of the study area resembled city parks, with several species typical for anthropogenic landscape.

Data on the distribution of Hystrichopsylla orientalis fleas (Siphonaptera) in Lithuania

The aim of this study was to present data on the distribution of Hystrichopsylla fleas collected from different animals in Lithuania. The study was done by analyzing collections of fleas from 2011 to 2017. A total of 96 fleas of the genus Hystrichopsylla were collected from nine mammalian species (Apodemus flavicollis, Apodemus agrarius, Micromys minutus, Myodes glareolus, Microtus oeconomus, Microtus arvalis, Sorex araneus, Neomys fodiens, and Glis glis). Morphological analysis showed that all fleas were of the species Hystrichopsylla orientalis Smit, 1956.

Flea Communities on Small Rodents in Eastern Poland.

Simple SummaryFleas are obligatory, secondarily wingless, hematophagous insects living all over the world. They colonize a variety of habitats from wet tropical forests to semi-arid and desert areas. Adult individuals feed mainly on small mammals, and less often on birds. The aim of the present study was to explore the fauna of fleas and their broad-sense behavior in eastern Poland. Rodents, which are widely recognized as one of the preferred hosts of these insects, were caught to carry out the study. The results show that, regardless of the ecological habitat type, the striped field mouse Apodemus agrarius was the most frequently captured rodent species, and the Ctenophthalmus agyrtes flea species was collected most frequently. Moreover, rhythms in the seasonal activity of fleas, with a peak in summer months, were noted.Fleas are hematophagous insects infesting mainly small mammals and, less frequently, birds. With their wide range of potential hosts, fleas play a significant role in the circulation of pathogens in nature. Depending on the species, they can be vectors for viruses, bacteria, rickettsiae, and protozoa and a host for some larval forms of tapeworm species. The aim of this study was to determine the species composition of fleas and their small rodent host preferences in eastern Poland. Animals were captured in traps in various types of ecological habitats (a site covered by grassland vegetation within city limits, an unused agricultural meadow, and a fallow land near a mixed forest). The following rodent species were caught: Apodemus agrarius, Apodemus flavicollis, Microtus arvalis, and Myodes glareolus. Additionally, Ctenophthalmus agyrtes, Ctenophthalmus assimilis, Hystrichopsylla talpae, and Nosopsyllus fasciatus flea species were identified. The peak of the flea activity was noted in summer months. C. agyrtes was found to be the most abundant flea species in eastern Poland, while the greatest numbers of fleas were collected from the rodent species A. agrarius.

Management Intensity and Forest Successional Stages as Significant Determinants of Small Mammal Communities in a Lowland Floodplain Forest

The conversion of forests from complex natural ecosystems to simplified commercial woodlands is one of the major causes of biodiversity loss. To maintain biodiversity, we need to understand how current management practices influence forest ecosystems. We studied the effects of forest successional stage and management intensity on the abundance, species richness, and assemblage composition of small mammals. Our results show that management intensity significantly contributes to reducing the number of species after clearcutting. We revealed that intensively managed clearings can make the dispersal or foraging activity of small mammals difficult and hence negatively influence their abundance and species richness. The significantly higher species richness of small mammal species was recorded within more extensively rather than intensively managed clearings. In contrast, we did not observe significant changes in species richness and abundance after intensive management in old-growth forests. Species Clethrionomys glareolus and Apodemus flavicollis reached the greatest abundance in old-growth forest patches. On the other hand, Microtus arvalis and Microtus subterraneus were species mainly associated with the successionally youngest forest stands. Our analysis suggests that intensive management interventions (i.e., vegetation destruction by pesticides and wood debris removal by soil milling) in clearings produce unhostile environments for majority of the small mammal species.

What determines species composition and diversity of hypogeous fungi in the diet of small mammals? A comparison across mammal species, habitat types and seasons in Central European mountains

Interactions between diverse groups of organisms influence the functioning and diversity of ecosystems. Salient examples of such relationships are those among hypogeous fungi, trees and mycophagous mammals. To investigate the role of small mammals in transporting fungal spores within and outside forests as well as the influence of seasons, habitats and species on small mammal mycophagy, we set up a study in the Pieniny Mts, Western Carpathians (Southern Poland). The droppings of small mammals were collected during live trapping in July and September 2016 and 2017, to analyze richness, composition and frequency of fungal spores present in faeces. The yellow-necked mouse Apodemus flavicollis, the bank vole Myodes glareolus and the common vole Microtus arvalis were the most frequently trapped. Spores of 27 fungal taxa from 16 genera were retrieved from nearly 70% of faecal samples of rodents and shrews, with up to 9 spore taxa recorded per sample. Spore diversity in samples was higher in September than in July, although seasonal variation was year and animal dependent. The highest mean number of fungal taxa per sample was recorded for the bank vole and the yellow-necked mouse, with the former species showing a higher degree of mycophagy. The two rodents differed in the average frequencies of consumed fungi in samples, which could result from some degree of specialization in the choice of particular fungal species, as shown by the laboratory-based experiment. Within particular animal species, differences in the fungal diet were found between seasons. The spores of hypogeous fungi were transported from forests to meadows mostly by the yellow-necked mouse and, to a lesser extent, by the common vole. However, both, the diversity and the number of transported spores diminished with distance from the forest edge. • Rich and diverse assemblage of consumed hypogeous fungi in the Pieniny Mts. • Consumption of hypogeous fungi influenced by year, season, animal species and habitat. • Proves for a differential consumption of hypogeous fungi by rodent species. • Fungi are transported through the forest-meadow ecotone to the non-forest environments. • Yellow-necked mouse most effective in transporting fungal spores both in forests and in open areas.

Growth of the Hippocampus in Bank Voles (Clethrionomys glareolus, Rodentia) from Different Seasonal Generations

Age-related variations in the hippocampus mass in the late postnatal ontogeny of bank voles (Clethrionomys glareolus) from the spring and autumn generations are considered in a comparative aspect. The mass of the hippocampus of the spring voles increases regularly over their short life cycle and approaches the values maximum for the species at two months of age. In the autumn voles, a two-peak growth curve is detected, the hippocampus increasing until September, after which an autumn-winter regression of the mass of this brain region was observed. The hippocampal growth of autumn voles resumed at the age of 7–9 months and coincided with the beginning of the period of reproduction. The hippocampus of autumn voles reached a definitive size at the age of 10–11 months. The results obtained characterize specific features of hippocampal growth in spring and autumn voles. The mechanisms that switch the alternative types of ontogeny of the seasonal generations are discussed.

Increased sperm production linked to competition in the maternal social environment.

Maternal or early life effects may prepare offspring for similar social conditions to those experienced by their mothers. For males, the ability to achieve mating and fertilization success is a key social challenge. Competitive conditions may therefore favour increased body size or ejaculate production in male offspring. We tested this experimentally by comparing reproductive traits of adult male bank voles (Myodes glareolus), whose mothers had experienced contrasting encounter regimes with female conspecifics while breeding. We found that daily sperm production rates and epididymis mass were significantly higher when dams had experienced more frequent encounters with female conspecifics. This response to maternal and early life experience was specific to sperm production and storage, with no evidence for effects on male body mass or the size of testes and accessory reproductive glands. Our findings reveal a potentially adaptive effect of maternal and early life experience on the development of sperm production, which is worthy of wider investigation.

Puumala orthohantavirus genome sequence variations in the Republic of Tatarstan, Russia

Background: Hemorrhagic fever with renal syndrome (HFRS) is endemic in Republic of Tatarstan (RT), where Puumala orthohatavirus (PUUV) is identified as the main cause of infection. Eight genetic lineages of PUUV were shown to circulate in Eurasia; however, the diversity of PUUV variants in RT remains largely unknown. Methods & Materials: Total RNA extracted from lung tissues of bank voles captured in multiple location in RT was used for RT-PCR analysis. More than hundred PCR products containing partial S, M and L segments coding regions (566/1057, 1014 and 665 bp, respectively) were sequenced and used to determine genome variations. Results: Most of PUUV sequences revealed low divergence as compared to previously identified in Udmurtia, Bashkortostan and Samara. All these samples belong to the Russian lineage. Interestingly, in addition to the Russian lineage, three RT PUUV strains were part of the Finnish lineage, suggesting co-circulation of two PUUV lineages in some RT locations. Phylogenetic analysis revealed that RT PUUV partial S, M and L segments of RUS lineage formed six subclades, corresponding to their geographic locations in RT districts. Subclades I–IV contained strains from Pre-Kama area, subclade V strains are distributed in Trans-Kama area, while strains from subclade VI are found in Pre-Volga area. Subclades IV and V clustered together on the S and M segment trees, while subclade IV located as a separate group of the L segment. Also, subclade III clustered with subclade II for the S segment, with subclades IV–V for the M segment and with subclades I–II for the L segment. These differences in tree topologies suggest the reassortment or/and recombination origin of some PUUV strains circulating in the RT. Conclusion: Collected data improves our understanding of PUUV diversity and distribution in different regions of RT, which help better control the epidemiological situation in the region. The Russian Government Program of Competitive Growth of Kazan Federal University supported this study. Also, Albert Rizvanov was supported by state assignment 20.5175.2017/6.7 of the Ministry of Education and Science of the Russian Federation. Part of this work was conducted with the support of RFFI perspective grant 19-34-60012 given to Emmanuel Kabwe.

Alteration of neuro-dopamine and steroid hormone homeostasis in wild Bank voles in relation to tissue concentrations of PFAS at a Nordic skiing area

Perfluoroalkyl substances (PFAS) are contaminants that are applied in a wide range of consumer products, including ski products. The present study investigated the neuro-dopamine (DA) and cellular steroid hormone homeostasis of wild Bank voles (Myodes glareolus) from a skiing area in Norway (Trondheim), in relation to tissue concentrations of PFAS. We found a positive association between brain DA concentrations and the concentration of several PFAS, while there was a negative association between PFAS and dopamine receptor 1 (dr1) mRNA. The ratio between DA and its metabolites (3,4-dihydroxyphenylacetic acid: DOPAC and homovanillic acid: HVA) showed a negative association between DOPAC/DA and several PFAS, suggesting that PFAS altered the metabolism of DA via monoamine oxidase (Mao). This assumption is supported by an observed negative association between mao mRNA and PFAS. Previous studies have shown that DA homeostasis can indirectly regulate cellular estrogen (E2) and testosterone (T) biosynthesis. We found no association between DA and steroid hormone levels, while there was a negative association between some PFAS and T concentrations, suggesting that PFAS might affect T through other mechanisms. The results from the current study indicate that PFAS may alter neuro-DA and steroid hormone homeostasis in Bank voles, with potential consequences on reproduction and general health.

Interactive influences of fluctuations of main food resources and climate change on long-term population decline of Tengmalm\u2019s owls in the boreal forest

Recent wildlife population declines are usually attributed to multiple sources such as global climate change and habitat loss and degradation inducing decreased food supply. However, interactive effects of fluctuations in abundance of main foods and weather conditions on population densities and reproductive success have been studied rarely. We analysed long-term (1973–2018) data on Tengmalm’s owl (Aegolius funereus) and the influence of prey abundance and weather on breeding densities and reproductive success in western Finland. We found that fledgling production per breeding attempt declined and laying date of the owl population delayed during the period between 1973 and 2018. The breeding density of the owl population decreased with increasing temperature in winter (October–March), fledgling production increased with increasing temperature and precipitation in spring (April–June), whereas the initiation of egg-laying was delayed with increasing depth of snow cover in late winter (January–March). The decreasing trend of fledgling production, which was mainly due to starvation of offspring, was an important factor contributing to the long-term decline of the Tengmalm’s owl study population. Milder and more humid spring and early summer temperatures due to global warming were not able to compensate for lowered offspring production of owls. The main reason for low productivity is probably loss and degradation of mature and old-growth forests due to clear-felling which results in loss of coverage of prime habitat for main (bank voles) and alternative foods (small birds) of owls inducing lack of food, and refuges against predators of Tengmalm’s owls. This interpretation was also supported by the delayed start of egg-laying during the study period although ambient temperatures increased prior to and during the egg-laying period.