Effects of fitch odor (Mustila eversmanni) on behavior and breeding of root voles (Microtus oeconomus)

From April to December in 1997 at Northwest Plateau Institute of Biology, Chinese Academy of Science, the effect of predation risk on social behavior, feeding, reproduction and sexual hormones of the root voles (Microtus oeconomus) was studied when the root voles (Microtus oeconomus ) were exposed to the odor of fitch (Mustila eversmanni). The results showed that the root voles delayed breeding period and the frequency of the copulation significantly lowered (P【0.01). Comparing with the control group, the accumulated time of amicable behavior in females, and general activity of both sexes increased significantly (P【0.01). The frequencies of general activity (P【0.01), investigating activity (females: P【0.05, males: P【0.01), and self-grooming (P【0.01) of both sexes were less significantly. At the same time, the amount of energy intake (P【0.05) and body weight (P【0.01) of the root voles decreased significantly. The litter weight and ovary index of females decreased (P【0.01). For males the sperm count in epididymides also decreased significantly (P【0.01). The progesterone in the blood serum of root voles females increased significantly under fitch odor (P【0.01).

Effect of temperature on antioxidant defense and innate immunity in Brandt’s voles

Ambient temperature is an importa nt factor in flue ncing many physiological processes, in eluding antioxidant defense and immunity. In the present study, we tested the hypothesis that antioxidant defense and immunity are suppressed by high and low temperature treatme nt in Bran dt's voles (Lasiopodomys brandtii). Thirty male voles were randomly assigned into different temperature groups (4, 23, and 32℃, n=10 for each group), with the treatment course lasting for 27 d. Results showed that low temperature in creased gross en ergy in take (GEI) and liver, heart, and kidney mass, but decreased body fat mass and dry carcass mass. With the decline in temperature, hydrogen peroxide (H2O2) concentration, which is indicative of reactive oxyge n species (ROS) levels, in creased in the liver, decreased in the heart, and was unchanged in the kidney, testis, and small intestine. Lipid peroxidation indicated by malonaldehyde (MDA) content in the liver, heart, kidney, testis, and small intestine did not differ among groups, implying that high and low temperature did not cause oxidative damage. Similarly, superoxide dismutase (SOD) and catalase (CAT) activities and total antioxidant capacity (TAOC) in the five tissues did not respond to low or high temperature, except for elevation of CAT activity in the testis upon cold exposure. Bacteria killing capacity, which is indicative of innate immunity, was nearly suppressed in the 4℃ group in contrast to the 23℃ group, whereas spleen mass and white blood cells were un affected by temperature treatment. The levels of testosterone, but not corticostero ne, were in flue need by temperature treatment, though neither were correlated with innate immunity, H2O2 and MDA levels, or SOD, CAT, and TAOC activity in any detected tissues. Overall, these results showed that temperature had different in flue nces on oxidative stress, an tioxida nt en zymes, and immunity, which depended on the tissues and parameters tested. Up-regulation or maintenance of an tioxida nt defe nse might be an importa nt mechanism for voles to survive highly variable environmental temperatures.

Spontaneous emergence of overgrown molar teeth in a colony of Prairie voles(Microtus ochrogaster)

Continuously growing incisors are common to all rodents, which include the Microtus genus of voles. However, unlike many rodents, voles also possess continuously growing molars. Here, we report spontaneous molar defects in a population of Prairie voles （Microtus ochrogaster）. We identified bilateral protuberances on the ventral surface of the mandible in several voles in our colony. In some cases, the protuberances broke through the cortical bone. The mandibular molars became exposed and infected, and the maxillary molars entered the cranial vault. Visualisation upon soft tissue removal and microcomputed tomography （microCT） analyses confirmed that the protuberances were caused by the overgrowth of the apical ends of the molar teeth. We speculate that the unrestricted growth of the molars was due to the misregulation of the molar dental stem cell niche. Further study of this molar phenotype may yield additional insight into stem cell regulation and the evolution and development of continuously growing teeth.

Anti-fertility effect of levonorgestrel and quinestrol in Brandt’s voles(Lasiopodomys brandtii)

The combination of levonorgestrel and quinestrol(EP-1)has been shown to have anti-fertility effects on several wild rodents,but the mechanism underlying these effects is poorly understood.We investigated the effects of EP-1 and each of its components,levonorgestrel(P)and quinestrol(E),on the fertility of Brandt’s voles(Lasiopodomys brandtii)by using a gastric gavage method.The doses for EP-1,E and P were 1,0.34 and 0.66 mg/kg body weight,respectively.Male voles(n=98)were treated daily for 5 or 14 days,then the testes and epididymides were collected,weighed and examined histologically at 30(D30),60(D60)or 90(D90)days after the end of treatment.Four males were allowed to mate with normal females at D90.Female voles(n=75)were treated for 3 days and a further 3 days after a 7-day interval.The uteri and ovaries were weighed and examined histologically at 15(D15),30(D30)or 75(D75)days after the end of treatment.Each of three females were mated with fertile males at D30 and D75,respectively.Our results indicated that quinestrol(E)significantly decreased the sperm numbers in the testes as well as the weight of the testes and epididymides,with both of these tissues showing obvious structural abnormalities,and significantly reduced the litter size and the pup weight for females mated with males of the E treatment group.For female voles,treatment with E,P or EP-1 resulted in no marked influence on the fertility status.These data indicate that quinestrol(E)alone has a significant anti-fertility effect on male Brandt’s voles,but is ineffective in combination with levonorgestrel(P).

Large manipulative experiments reveal complex effects of food supplementation on population dynamics of Brandt's voles

Although food supplementation is well known to increase population density,there is still debate on the causative effects of food supplementation on reproduction,survival,and immigration.Large manipulative experiments,which exclude any confounding effects of dispersal and predation,are essential for clarifying the debate.In this study,we investigated the effects of food supplementation on Brandt's vole population dynamics and plant community in eight large enclosures(0.48 ha each) from2010 to 2014.Food supplementation showed significant positive effects on population density due to increases in recruitment;however,it showed a complex effect on survival of voles:positive in non-breeding seasons,but negative in breeding seasons.In addition,food supplementation increased the quality of plants(as reflected by increased crude protein content),but decreased the quantity of less preferred plants in experimental enclosures.Thus,food seems to have direct positive effects on small rodents through improvement of food supply and indirect negative effects through food-induced density-dependent effects,and may have long-term effects on rodents through altering plant community composition and abundance.

Relationship between El Nino /South Oscillation(ENSO) and population outbreaks of some lemmings and voles in Europe

Ecologists have been puzzled by population cycles of lemmings and voles for the over 70 years. At present, our understanding and explanation to this phenomenon remain controversial. Recently, El Nino/South Oscillation has attracted attention of ecologists on its links with population outbreaks of terrestrial animals. This paper aims to investigate the statistical relationship between outbreaks of microtine rodents and ENSO events by scanning available literature. During 1862-1894, outbreaks of Norway lemmings in Norway tended to occur in the Southern Oscillation Index (SOI) peak years or 1 year after the SOI peak years with an approximate significance level (p = 0.057). During 1885-1931, outbreaks of voles in France tended to occur 1 year before the SOI peak years (p = 0.01). During 1946-1993, outbreaks of lemmings and voles in North Finland tended to occur 1 year before the SOI peak years with a significant level (p = 0.022); the peaks of population abundance corresponded well to the SOI trough years

The duration of sociosexual behaviors in male meadow voles Microtus pennsylvanicus varies before, during, and after copulation

The behaviors that surround copulation are characterized as sociosexual behaviors. These behaviors displayed by males that are directed at females may include allogrooming, wrestling, chasing, approach, and time spent together. The data supported the hypothesis that the duration of sociosexual behaviors differs during the pre-copulatory, peri-copulatory, and post-copulatory phases of the mating bout in meadow voles. Voles spent more time approaching conspecifics during the pre- and peri-copulatory phases than during the post-copulatory phase. Voles spent more time allogrooming, wrestling, and chasing during the pre-copulatory phase than during the peri- and post-copulatory phases. Voles spent similar amounts of time together during the pre-, peri-, and post-copulatory phases. The data suggest that sociosexual behaviors displayed by males may be involved in set- ring the pace and temporal components of the mating bout. During the pre-copulatory phase particular behaviors by male voles may attract females, during the peri-copulatory phase some of these behaviors may stimulate or motivate the female to mate, and during the post-copulatory phase certain behaviors may prepare the male to mate again

Male and female meadow voles Microtus pennsylvanicus respond differently to scent marks from the top- middle-, and bottom-scent donors of an over-mark

Previous studies have shown that individuals responded preferentially to the mark of the top-scent donor relative to that of the bottom-scent donor of an over-mark. However, terrestrial mammals are likely to encounter over-marks consisting of the scent marks of more than two same-sex conspecifics in the intersections of runways, near the nests of sexually receptive female conspecifics, and inside and along the borders of the territories of conspecifics. We determined how meadow voles, Microtus pennsylvanicus, respond to the marks of the top-, middle-, and bottom-scent donors of an over-mark. We tested the hypothesis that voles exposed to an over-mark will respond preferentially to the scent marks that were deposited more recently, the scent marks that were on top or near the top of the over-mark, compared to the scent marks that were deposited earlier or near the bot- tom of the over-mark. Voles spent more time investigating the mark of the top-scent donor than that of the either the middle- or bottom-scent donor. However, males but not female voles spent more time investigating the middle-scent mark than the bot- tom-scent mark. We also tested the hypothesis that voles evaluate and respond to over-marks differently from single scent marks. Voles spent more time investigating the marks of the top-, middle-, and bottom-scent donors compared to scent marks that were not part of the over-mark. Voles can distinguish among the overlapping scent marks of three scent donors and sex differences exist in the values they appear to attach to each of these scent marks [Current Zoology 57 （4）： 441-448, 2011 ].

Evolutionary history of mountain voles of the subgenus Aschizomys (Cricetidae, Rodentia), inferred from mitochondrial and nuclear markers

In this study,we present an assessment of the evolutionary history and phylogenetic relationships of Asian mountain voles of the subgenus Aschizomys,genus Alticola,based on extensive sampling and phylogenetic analyses of data from mitochondrial and nuclear markers.Two species of this subgenus are widespread in the mountain areas of north-eastern Asia.However,both their distribution and taxonomic borders remained questionable for more than 100 years.Our study showed discordance in the phylogenetic patterns between nuclear and mtDNA markers.We found that mtDNA in A.lemminus is paraphyletic relative to A.macrotis,but nuclear markers demonstrated reciprocal monophyly.According to species distribution modeling,ranges of A.macrotis and A.lemminus experienced a secondary contact during the Last Glacial Maximum(approximately 22 kyr BP),and thus a hybridization event seems plausible during that period.Species tree analyses recovered a sister group relationship between the two species of the Aschizomys subgenus,with an estimated divergence date of around 0.8 Ma.Our results provided good support for currently recognized subspecies within both A.macrotis and A.lemminus based on mitochondrial and nuclear datasets.A new,yet undescribed form,supposedly of a subspecific status within A.lemminus,was found in the Bureinskiy Range in the Khabarovsk area.This finding expands the current species distribution range further to the southeast.

Kinship analysis reveals reproductive success skewed toward overwintered Brandt’s voles in semi-natural enclosures

Age structure and seasonality influence the population fluctuations of small rodents.Age determines body weight and social experience,while seasonality regulates the duration of the breeding season and onset of sex­ual maturity in newborn offspring.Therefore,reproductive success and skew usually occur in different age groups.Brandt’s vole(Lasiopodomys brandtii)is a social,short-lived and seasonal breeding small rodent with a dramatic seasonal population fluctuation,but reproductive skew is not fully understood in this species.In the present study,we determined kinship in semi-natural enclosure populations using microsatellite markers based on genotyping,analyzed the reproductive skew between sexes and between overwintered and newborn voles,and monitored variation in male reproductive activity by testing fecal testosterone levels throughout the year.Overwintered voles had the most reproductive success along with a striking increase in the population size in the enclosures,with all biological fathers and 77.8%of biological mothers,which had 100%and 87%of the to­tal offspring,respectively.Compared to overwintered voles,reproductive skews were significantly higher in po­tential overwintered and newborn parents,implying the possible reproductive suppression of newborn voles by dominant overwintered voles.Moreover,both heavier body weight and higher testosterone levels in overwin­tered males supported their potential social status in the population.Our study provided new evidence for repro­ductive skew and differentiation of postnatal gonadal development patterns of different age groups in Brandt’s vole.

Guild composition and habitat use of voles in 2 forest landscapes in south-eastern Norway

It is widely believed that intensive forestry has influenced small mammal population dynamics,and thereby the entire mammalian community in Fennoscandian boreal forests.The nature of these impacts on the different species is subject to debate.We live-trapped voles between 2006 and 2009 in 2 commercially harvested forests in south-eastern Norway.We investigated the variation in vole abundance among habitat types(e.g.mature forest and clear-cut)and the hypothesis that graminivorous species such as field voles(Microtus agrestis L.)benefit from clear-cuts at the expense of forest dwellers(i.e.the bank vole,Myodes glareolus Schreb.),using fine-scale descriptors of the ground vegetation.We could not find support for the hypothesis that field voles show a preference for clear-cuts,and their overall abundance was low,while bank voles were the dominant species in all habitat types,including clear-cuts in the peak and pre-peak years.We found a positive association between bank vole abundance and bilberry(Vaccinium myrtillus L.)availability rather than a specific habitat type.Low field vole density in clear-cuts might be due to variation in local productivity and ground vegetation as well as to large variation in the species temporal dynamics.The latter is particularly associated with the widespread decline of field voles in Scandinavia.Logging has the potential to negatively affect bank vole population dynamics because of the negative effect on bilberry development.

Early developmental exposure to inorganic mercury does not alter affiliative behavior of adult prairie voles(Microtus ochrogaster)

Mercury chloride exposure through drinking water in adult male prairie voles(Microtus ochrogaster)has been shown to alter their social behavior.Here,we examined the potential disruption of adult social behavior in prairie voles that were exposed to 60 ppm mercury during early development.We used a cross-fostering approach to test the effects of mercury exposure:(1)from conception until birth;(ii)from birth until weaning;and(iii)from conception until weaning,on adult affiliative behavior.Untreated and mercury-treated voles were given the option of remaining in an empty cage or affiliating with a same-sex conspecific in a 3-h choice test.We found that early developmental mercury exposure had little if any effect on the reproductive success of breeder pairs or on affiliative behavior by either sex when subjects were tested as adults.These results suggest that,at least in the context of the behavior tested,the effects of early developmental exposure to mercury do not permanently alter adult prairie vole affiliative behavior,or do so in a way that is too subtle to be detected using the current testing paradigm.

Habitat evaluation for outbreak of Yangtze voles(Microtus fortis)and management implications

Rodent pests severely damage agricultural crops.Outbreak risk models of rodent pests often do not include sufficient information regarding geographic variation.Habitat plays an important role in rodent-pest outbreak risk,and more information about the relationship between habitat and crop protection is urgently needed.The goal of the present study was to provide an outbreak risk map for the Dongting Lake region and to understand the relationship between rodent-pest outbreak variation and habitat distribution.The main rodent pests in the Dongting Lake region are Yangtze voles(Microtus fortis).These pests cause massive damage in outbreak years,most notably in 2007.Habitat evaluation and ecological details were obtained by analyzing the correlation between habitat suitability and outbreak risk,as indicated by population density and historical events.For the source-sink population,96.18%of Yangtze vole disaster regions were covered by a 10-km buffer zone of suitable habitat in 2007.Historical outbreak frequency and peak population density were significantly correlated with the proportion of land covered by suitable habitat(r=0.68,P=0.04 and r=0.76,P=0.03,respectively).The Yangtze vole population tends to migrate approximately 10 km in outbreak years.Here,we propose a practical method for habitat evaluation that can be used to create integrated pest management plans for rodent pests when combined with basic information on the biology,ecology and behavior of the target species.

Specialist predator in a multi-species prey community:boreal voles and weasels

Dissimilar vulnerabilities of different prey types and preferences of predators are factors likely to contribute to community dynamics.This may happen via differential individual properties of prey animals(e.g.vigilance,escape)or via habitat effects making hunting by a predator easier and more rewarding in some habitats,or both.Furthermore,community dynamics may be influenced by predator mediated apparent competition,in which an increase in one prey type has negative effects on another prey type indirectly via the shared predator.We summarize the current knowledge from the field in a model predator–prey system consisting of sympatric boreal vole species and their common specialist predator and review field studies using predator manipulation and studies on the responses of individuals in the laboratory and in outdoor enclosures.The vole species studied represent different prey types that are thought to have different vulnerabilities.Our observations on the main resident specialist predator,the least weasel(Mustela nivalis nivalis L.),show that it hunts according to prey availability and suitability of the hunting habitat.Prey voles respond to the presence of the predator behaviorally in various ways to avoid predation.We conclude that even if the least weasel is a specialized predator of small rodents it acts like a generalist predator within the small rodent guild and may facilitate the coexistence of prey species via predator switching.This may lead to interspecific synchrony between prey populations,which has often been observed.We suggest that the processes determining the community impact of predator–prey interactions are driven by the behavioral arms race between the predator and the prey,together with the habitat-dependent density of prey and net gain for the predator.

Changes of Estrogen in Serum and Estrogen Receptor β in the Relevant Brain Regions Following Mating Behavior of the Male Mandarin Vole Microtus mandarinus

In order to investigate the estrogen and estrogen receptor β changes after mating behavior of male mandarin vole （Microtus mandarinus）, the radioimmunoassay （RIA） and immunohistochemistry methods were used to investigate changes of the serum estrogen （E） concentrations, estrogen immunoreactive neurons （E-IRs） and estrogen receptor β immunoreactive neurons （ERβ-IRs） in the relevant brain regions following mating behavior. Fifteen sexually matured male voles were randomly divided into three groups and treated differently： （1） control group： voles were exposed to clean hard-wood shavings （n=5）, （2） exposure group： voles were exposed to the soiled bedding for more than 24h on which estrous females had been placed （n=5）, and （3） mating group： voles were placed with an estrous female for more than 24h （n=5）. The results showed circulating serum E concentrations were significantly higher in the mating group than in the exposure group and the control group, and there were no significant difference between the exposure group and the control group. E-IRs and ERβ-IRs were detected in the following brain regions related to mating behavior： the arcuate nucleus （ARC）, bed nucleus of the stria terminalis （BST）, lateral septal nucleus （LS）, medial amygdaloid nucleus （ME）, medial preoptic area （MPO） and ventromedial hypothalamic nucleus （VMH）. The results showed that there were significantly more E-IRs in the six brain regions in the mating group than in the control group and the exposure group, and there were no significant difference between the exposure group and the control group except for LS. There was no significant difference in ERβ-IRs in the six brain regions among the three groups, and there were some lighter -stained ERβ-IRs in these brain regions. The results suggested that estrogen affect mating activity of male mandarin voles, but ERβ might not play an important role in mating behavior of male mandarin voles. Instead, it might be through other receptors.

Small mammal community response to early meadow–forest succession

Background： With farmland afforestation becoming common policy in many European Union countries, we studied how early forest succession（from meadow to young stand） influences small mammal species composition, diversity,abundance and biomass. Despite numerous investigations into forest succession, almost no attention has been given to the small mammal community change in the early-successional forest ecosystems, starting with the pre-forest habitat and ending with stand formation and the establishment of tree dominance. We compared small mammal communities in meadows at the initial stage of regrowth（with saplings less than 10 cm in height）, in young forest（5–10 years old） and more advanced forest（15–20 years） in both cases of human-induced forest succession, where the trees had been planted, and natural forest succession, where natural regrowth of meadows had occurred.Results： The greatest diversity of small mammal species was recorded in the meadow（H = 2.95）, with a lower diversity found in the young forest（H = 2.61） and even lower in the advanced forest（H = 2.04）, the last habitat being the most monodominantic. The order of species dominance from Microtus sp.（M. arvalis, M. agrestis）, Myodes glareolus, Apodemus flavicollis, Sorex araneus, A. agrarius in the meadow changed to M. glareolus, S. araneus, M. arvalis,M. agrestis in the young forest and to M. glareolus, A. flavicollis, S. araneus in the advanced forest. The lowest relative abundance of small mammals was recorded in the meadow（18.19 ± 2.27 ind. Per 100 trap-days）, with Microtus voles being the most abundant. Relative abundance was higher in the young forest（22.72 ± 2.25 ind. Per 100 trap-days）,with Myodes glareolus being the most abundant（7.59 ± 0.96 ind. Per 100 trap-days） and at its highest in the advanced forest（23.91 ± 2.77 ind. Per 100 trap-days）, again with M. glareolus being the most abundant（15.54 ± 2.35 ind. Per100 trap-days）.Conclusions： Thus, our analysis suggests that that during early meadow-forest succession, the diversity of the small mammal community declines – the number of species decreases as typical meadow species are lost due to the transformation of the habitat and one or a few species became dominants. However, the relative abundance of the small mammals increases. Biological indices of small mammal communities differed between natural and humaninduced meadow-forest succession.

Mating behavior induces changes of expression of Fos protein,plasma testosterone and androgen receptors in the accessory olfactory bulb (AOB) of the male mandarin vole Microtus mandarinus

In order to investigate the neuroendocrine mechanism of the mating behavior in the adult male mandarin voles Microtus mandarinus,the radioimmunoassay(RIA)and immunohistochemistry methods were used to investigate the differences in plasma testosterone(T)concentrations and distribution of T immunoreactive neurons(T-IRs),androgen receptor immunoreactive neurons(AR-IRs)and Fos protein immunoreactive neurons(Fos-IRs)in the accessory olfactory bulb(AOB)and the main olfactory bulb(MOB)following exposure to clean hard-wood shavings(control group),soiled bedding(exposure group)or contact with an estrous female(mating group).Results showed that plasma T concentration was significantly higher in the mating group than that in the exposure group,and both the mating group and the exposure group displayed significantly higher plasma T concentration than the control group.T-IRs,AR-IRs and Fos-IRs were investigated with the immunohistochemistry method in granule cell(GC)and mitral cell(MC)of the MOB and the AOB in the three groups.There were significantly more T-IRs,AR-IRs and Fos-IRs in MC and GC of the AOB in the mating group than that in the exposure group or the control group.T-IRs,AR-IRs and Fos-IRs did not show significant differences between the exposure group and the control group.Furthermore,obvious differences in MC and GC of the MOB were not found among the three groups.The results confirm that both changes of T and AR in the AOB might be underlying mating behavior in the adult male mandarin voles.

Comparison of social interaction and neural activation in the main olfactory bulb and the accessory olfactory bulb between Microtus mandarinus and Microtus fortis

To gain insight into the function of AOB and MOB during different social interaction and in different vole species,the behaviors and neural activation of the olfactory bulbs in social interactions of mandarin voles Microtus mandarinus and reed voles Microtus fortis were compared in the present research.Mandarin voles spent significantly more time attacking and sniffing their opponents and sniffing sawdust than reed voles.During same sex encounters,mandarin voles attacked their opponents for a significantly longer time and sniffed its opponent for shorter time compared with male-female interactions.However,no significant behavioral differences were found during encounters of two individual reed voles,regardless of gender composition of the pair.Using c-Fos as an indicator of neural activation,we observed that neural activation was significantly higher in almost all sub-regions of the main olfactory bulb(MOB)and the accessory olfactory bulb(AOB)of mandarin voles compared with reed voles.Numbers of c-Fos-ir neurons in almost all sub-regions of the AOB and the MOB during male-female interactions were also higher than those in interactions of the same sex.Anterior-posterior ratios of Fos-ir neurons in the AOBM(AOBMR)and the AOBG(AOBGR)in male-female interaction were significantly higher than those in interaction of the same sex.The AOBMR of male mandarin voles and reed voles were larger than those of females in male-female interactions.Behavioral patterns are consistent with cellular activity patterns.Consistent level of neural activation in MOB and AOB suggests important roles of both the main olfactory bulb and the accessory olfactory bulb in social interaction in two species.

Interactions between intruders and residents in the mole vole Ellobius talpinus

We studied the behavioral and endocrine responses of the fossorial s ocial rodent, mole vole Ellobius talpinus Pall., to intrusions of strangers int o burrow systems that were occupied by intact families. Both in reproductive and non-reproductive seasons, all intruders disappeared from the burrow systems of residents within two days of introduction, whereas 4 of 7 individuals introduced into empty burrows remained there at least for two days. Introduction of strang ers led to the concentration of residents at the point of release and to an incr ease of plasma corticosterone in both residents and intruders. During the breedi ng season, introduction of strangers was also accompanied by an increase of plas ma testosterone of residents on the day of introduction. Thus, simulation of int rusion of strangers demonstrated the efficient social fence of resident mole vol es that seems to be an important mechanism of stabilization of size and structur e of mole vole families. Encounters of residents and intruders resulted in activ ation of physiological mechanisms of stress, especially during the breeding seas on .

Small mammal community composition impacts bank vole (Clethrionomys glareolus) population dynamics and associated seroprevalence of Puumala orthohantavirus

Rodents are important reservoirs for zoonotic pathogens that cause diseases in humans.Biodiversity is hypoth-esized to be closely related to pathogen prevalence through multiple direct and indirect pathways.For example,the presence of non-host species can reduce contact rates of the main reservoir host and thus reduce the risk of transmission(“dilution effect”).In addition,an overlap in ecological niches between two species could lead to increased interspecific competition,potentially limiting host densities and reducing density-dependent pathogen transmission processes.In this study,we investigated the relative impact of population-level regulation of direct and indirect drivers of the prevalence of Puumala orthohantavirus(PUUV)in bank voles(Clethrionomys glareolus)during years with high abundance.We compiled data on small mammal community composition from four regions in Germany between 2010 and 2013.Structural equation modeling revealed a strong seasonality in PUUV control mechanisms in bank voles.The abundance of shrews tended to have a negative relationship with host abundance,and host abundance positively influenced PUUV seroprevalence,while at the same time increasing the abundance of competing non-hosts like the wood mouse(Apodemus sylvaticus)and the yellow-neckedfield mouse(Apodemusflavicollis)were associated with reduced PUUV seroprevalence in the host.These results indicate that for PUUV in bank voles,dilution is associated with increased interspecific competition.Anthropogenic pressures leading to the decline of Apodemus spp.in a specific habitat could lead to the amplification of mechanisms promoting PUUV transmission within the host populations.