Apodemus Sylvaticus Research Articles

Different alternative diets within two subgroups in a winter roost of long-eared owls

Abstract In winter 2013/2014 a roost of long-eared owls in Bojnice Spa (central Slovakia) was formed by two subgroups situated 12 meters apart from each other. The diets of both subgroups and the direction of the owls’ departure from the roost were studied at monthly intervals. Owls of the Pinus-subgroup left the roost in a significantly different direction compared with the owls in the Picea-subgroup. The common vole was the most hunted prey in both subgroups. However, comparing the alternative prey of the two subgroups, the wood mouse and other mammals were found significantly more often in pellets of the Picea-sub-group, whereas birds were more frequent in pellets of the Pinus-subgroup. Our results suggest that the different prey hunted by the two subgroups may be a consequence of diverging hunting areas with different availability of alternative prey species.

Skull Sizes and Proportions in Western Palearctic Wood Mice (Sylvaemus, Muridae, Rodentia) from Eastern Europe: 2. Intraspecific Variability

Skull Sizes and Proportions in Western Palearctic Wood Mice (Sylvaemus, Muridae, Rodentia) from Eastern Europe: 2. Intraspecific Variability

Skull Sizes and Proportions in Western Palearctic Wood Mice (Sylvaemus, Muridae, Rodentia) from Eastern Europe: 1. Interspecific Variability

Craniometric features (measurements, indexes) in several species of the genus Sylvaemus (S. sylvaticus, S. flavicollis, and S. uralensis from Eastern Europe and some adjacent territories, as well as S. ponticus and S. witherbyi from the Caucasus) have been studied using multivariate statistical analysis. For the first time, craniometric characters of the genus Sylvaemus are considered in relation to the feeding ecology of species. A total of 614 skulls were studied. Based on original material, discriminant keys have been developed using skull measurements. The keys appear to be suitable for the diagnostics of the studied Sylvaemus species, including sibling ones. The largest skulls are shown to be characteristic of S.flavicollis, and the smallest ones, of S. uralensis. Cluster analysis of the absolute measurements of the skull cumulative selection has revealed the greatest isolation of S. flavicollis and the similarity of coexisting but phylogenetically remote S. ponticus and S. witherbyi. Factor analysis showed that, within the genus Sylvaemus, the general sizes are less essential than the characters related to food smashing (the length of the lower jaw and rostrum, the width of the occipital part of the skull), and possibly also to the thickness of the incisors. Comparative analyses of the relative skull measurements (the indexes related to the food preferences of the animals, granivory or folivory) allow us to conclude that the food adaptations to granivory in the structure of the skull and teeth increase in the series S. uralensis–S. sylvaticus–S. witherbyi–S. flavicollis–S. ponticus. The cranial evolution in species within the genus Sylvaemus is suggested to have been directed to increased adaptations in the mechanisms in seed peeling and processing.

Proximate causes and fitness consequences of double brooding in female barn owls.

Multiple brooding, reproducing twice or more per year, is an important component of life-history strategies. However, what proximate factors drive the frequency of multiple brooding and its fitness consequences for parents and offspring remains poorly known. Using long-term longitudinal data, we investigated double brooding in a barn owl population in France. We assessed the effects of both extrinsic and intrinsic factors and the consequences of double brooding on fledgling recruitment and female lifetime reproductive success. The occurrence of double brooding in the population, ranging from 0 to 87%, was positively related to the number of rodent prey stored at the nest. Females laying early in the season were more likely to breed twice and the probability of double brooding increased with smaller initial brood size, female age and the storage of wood mice at the nest early in the season. Fledglings from first broods recruited more often (8.2%) than those from single broods (3.8%) or second broods (3.3%), but this was primarily the consequence of laying dates, not brood type per se. Females producing two broods within a year, at least once in their lifetime, had higher lifetime reproductive success and produced more local recruits than females that did not (15.6 ± 8.1 vs. 6.1 ± 3.8 fledglings, 0.96 ± 1.2 vs. 0.24 ± 0.6 recruits). Our results suggests that the fitnessbenefits of double brooding exceed costs and that within-year variability in double brooding may berelated to heterogeneity in individual/territory quality.

Tigray Orthohantavirus Infects Two Related Rodent Species Adapted to Different Elevations in Ethiopia.

Orthohantaviruses are RNA viruses that some members are known to cause severe zoonotic diseases in humans. Orthohantaviruses are hosted by rodents, soricomorphs (shrews and moles), and bats. Only two orthohantaviruses associated with murid rodents are known in Africa, Sangassou orthohantavirus (SANGV) in two species of African wood mice (Hylomyscus), and Tigray orthohantavirus (TIGV) in the Ethiopian white-footed rat (Stenocephalemys albipes). In this article, we report evidence that, like SANGV, two strains of TIGV occur in two genetically related rodent species, S. albipes and S. sp. A, occupying different elevational zones in the same mountain. Investigating the other members of the genus Stenocephalemys for TIGV could reveal the real diversity of TIGV in the genus.

Parasite Load and Site-Specific Parasite Pressure as Determinants of Immune Indices in Two Sympatric Rodent Species.

Simple SummaryWild animals can host diseases that affect humans (i.e., zoonotic diseases). However, not all wild animals are equal in their hosting capacities. In fact, the immune system, the main defense against diseases, varies within and among species. Within species, variation relates to two factors: parasite load and parasite pressure. Parasite load refers to the amount of parasites in or on an individual. Parasite pressure refers to the amount of parasites in a location. The importance of these factors in shaping the immune system of wild rodents, a group of animals known to host zoonotic diseases, is poorly understood. Overall, the rodent species we studied (bank voles and wood mice) hosted 5 microparasites, 9 ectoparasites, and 8 gastrointestinal parasites. We found that parasite load and parasite pressure related to different facets of the immune system. We also found that bank voles exhibited higher levels of one immune defense than wood mice, but higher levels of this defense correlated with a worm infection only in wood mice. Lastly, a white blood cell ratio correlated with infection by a zoonotic parasite. Studies like ours help to document the complexities of host–parasite interactions and how these interactions shape zoonotic disease risk in a changing world.Wildlife is exposed to parasites from the environment. This parasite pressure, which differs among areas, likely shapes the immunological strategies of animals. Individuals differ in the number of parasites they encounter and host, and this parasite load also influences the immune system. The relative impact of parasite pressure vs. parasite load on different host species, particularly those implicated as important reservoirs of zoonotic pathogens, is poorly understood. We captured bank voles (Myodes glareolus) and wood mice (Apodemus sylvaticus) at four sites in the Netherlands. We sampled sub-adult males to quantify their immune function, infestation load for ecto- and gastrointestinal parasites, and infection status for vector-borne microparasites. We then used regression trees to test if variation in immune indices could be explained by among-site differences (parasite pressure), among-individual differences in infestation intensity and infection status (parasite load), or other intrinsic factors. Regression trees revealed splits among sites for haptoglobin, hemagglutination, and body-mass corrected spleen size. We also found splits based on infection/infestation for haptoglobin, hemolysis, and neutrophil to lymphocyte ratio. Furthermore, we found a split between species for hemolysis and splits based on body mass for haptoglobin, hemagglutination, hematocrit, and body-mass corrected spleen size. Our results suggest that both parasite pressure and parasite load influence the immune system of wild rodents. Additional studies linking disease ecology and ecological immunology are needed to understand better the complexities of host–parasite interactions and how these interactions shape zoonotic disease risk.

From mice to men: Three cases of human infection with Cryptosporidium ditrichi

Most human cases of cryptosporidiosis are caused by Cryptosporidium parvum or Cryptosporidium hominis. However, the number of recognised Cryptosporidium species, some of which are capable of infecting humans, is continuously increasing. Here we present three human cases infected with Cryptosporidium ditrichi, a recently described species in Apodemus spp. (striped field mouse, yellow-necked mouse, and wood mouse) from various European countries. All three patients were infected in Sweden, but in different years and in different parts of the country. Two patients, from whom clinical data were available, showed symptoms consistent with cryptosporidiosis. For one patient, epidemiological data indicated a possible close contact with mice. The obtained sequences at the small subunit rRNA, actin, and Cryptosporidium oocyst wall protein loci showed 100% identity to C. ditrichi isolates from Apodemus spp., while no 70 kDa heat shock protein gene sequences from C. ditrichi were available for comparison. This study shows the importance of including molecular typing in Cryptosporidium surveillance programmes, and it adds one more species to the plethora of Cryptosporidium spp. hitherto diagnosed in Swedish patients.

Body size and habitat use of the common weasel Mustela nivalis vulgaris in Mediterranean farmlands colonised by common voles Microtus arvalis

Small mustelids such as weasels are highly specialized predators of small rodents. Their diminutive size allows hunting for prey underground, but also means that they are “bite-sized” predators, preyed upon by other larger predators. Habitat use by weasels is therefore expected to depend not only on prey abundance, but also on predation risk. We report here on the body size and habitat use of common weasels Mustela nivalis vulgaris captured in intensive farmlands of northwest Spain during 2009–2015. We show that weasels’ capture rate was higher in field margins than in other habitats (cereal and alfalfa fields, fallows) irrespective of season. All small mammals (common vole, wood mouse, Algerian mouse, and greater white-toothed shrew) were consistently more frequently captured in field margins than other habitats. Weasel capture rate in each habitat was proportional to that of prey in these (alfalfa > fallows > cereal), except for field margins, which were used more intensively than expected from prey capture rate. Weasel capture rate was 37% lower in areas provided with nest boxes to increase local raptor abundance, a reduction that occurred in all habitats and was significant when correcting for prey capture rate. Weasel habitat use reflected a trade-off between prey abundance (bottom-up control) and predation risk (top-down control), with a preferential use of field margins that offer not only more prey but also permanent vegetation cover and protection from avian predators throughout most of the annual crop cycles. Weasel and vole head width data show that voles are not safe underground from smaller female weasels and that burrow entrances were wide enough for weasels to escape underground from predators. In NW Spain, common voles are a main farmland pest causing significant impacts. We discuss the implications of current vole control measures for weasels in areas recurrently affected by vole outbreaks.

When food access is challenging: evidence of wood mice ability to balance energy budget under predation risk and physiological stress reactions

Prey species must balance the energetic cost of locomotion, foraging effort, and predation risk. In our work, we assessed how the wood mice (Apodemus sylvaticus) balance these costs by manipulating food access difficulty and predation risk. Live trapping was conducted in Madrid (Spain) where 80 Sherman traps were set in four different plots. To assess how wood mice manage their energy budget, all traps were first subjected to a control period followed by four treatments of 3-day duration in which food access was experimentally manipulated (free access, straw balls, straw balls wrapped in metal wire, opened plastic bottles, closed bottles). Predation risk was simulated by exposing half of the traps to fox feces. To quantify food intake, we weighed the remnants of food left by each captured mouse. Furthermore, we collected mouse fecal samples from traps to evaluate the physiological stress response by quantifying fecal corticosterone metabolites (FCM). Results showed that despite mice generally avoiding traps treated with fox feces, predation risk did not modulate food intake or FCM levels. By contrast, the experimental manipulation of food access determined the amount eaten and increased FCM levels, probably owing to the different degrees of difficulty and the energy required to obtain the food. Moreover, recaptured individuals ate more, indicating that experience critically determines mice ability to reduce the costs of accessing food. By analyzing the joint variation between mice intake and FCM levels depending on food restriction treatments, we found that mice were able to modulate their energetic expenditure depending on food access difficulty probably in order to achieve a positive marginal value of energy. For wild animals, to optimally balance the energetic budget is critical to maximize fitness. However, foraging decisions are influenced by numerous internal and external factors which are poorly understood. We studied free-ranging mice behavioral and physiological stress response to different food restriction treatments, testing also the influence of predation risk and experience. We found that predation risk modulated mice capturability but not the feeding behavior or the stress response. We also discovered that mice seem to be able to adjust energy allocation when a novel resource appear, and that energy budget optimization may be mediated via glucocorticoid release and individuals experience.

Cold temperature improves tannin tolerance in a granivorous rodent.

The foraging ecology of mammalian herbivores is regulated in part by their ability to detoxify plant secondary metabolites (PSM). Ambient temperature has been shown to alter liver function in rodents and the toxicity of some PSMs, but little is known about the physiological and nutritional consequences of consuming PSMs at different ambient temperatures. Furthermore, the effect of ambient temperature on the response of mammals to the most ubiquitous class of PSM, tannins, is unknown. We measured the effect of temperature and tannin intake on liver function, and the subsequent effect on the tannin tolerance of wild Japanese wood mice, Apodemus speciosus. The experiment involved acclimation to one of two ambient temperatures (10°C or 20°C) followed by acclimation to a diet of acorns (6.2% tannin DW). Liver function was measured both before and after acclimation to acorns by measuring the clearance time of a hypnotic agent. Finally, the mice were fed only acorns in a 5-day feeding experiment to assess their tolerance to tannin in the diet. Acclimation to acorns had a significant effect on liver function, but the direction of this effect was dependent on ambient temperature. Acorn consumption improved the liver function of wood mice at 10°C, but reduced liver function at 20°C, revealing a complex relationship between ambient temperature and tannin intake on liver function. Furthermore, mice with better liver function, indicated by faster clearance of the hypnotic agent, exhibited higher protein digestibility on an acorn-only diet, indicative of higher tannin tolerance. These results suggest that environmental temperature plays a significant role in the tolerance of A.speciosus to tannins, providing new insight into their seasonal feeding behaviour and winter ecology. We contend that cold-induced tannin tolerance may help to explain the population dynamics of mammalian herbivores with seasonal changes in the tannin content of their diet, and inform predictions about the response of these animals to a changing climate.

Investigation on Diet of Long-Eared Owl (Asio Otus) Inhabiting Fatih Natural Park (Turkey)

Pellet analyses were used to identify small mammal species in the diet of this owl species in order to reveal its ecological role. In this study, 706 pellets of Asio otus were collected from 3 different localities in Fatih Natural Park between February and March 2014. Pellets were dissolved by using 3% NaOH solution and then bones were dehydrated and identified. The aim of this study was to determine mammal composition in the diet of Asio otus inhabiting Fatih Natural Park of Yozgat Province, Turkey. Residues of bone from 1293 individuals/preys corresponding to 42377.41 g biomass in total were detected as the result of analysis. These individuals were identified to belonging to 12 mammal species ( Crocidura suaveolens , Suncus etruscus , Microtus hartingi/lydius , Microtus levis , Microtus sp., Cricetulus migratorius , Mesocricetus brandti , Apodemus sp., Apodemus sylvaticus , Apodemus whitherbyi , Mus macedonicus , and Meriones tristrami ) from 3 families and 8 genera. Microtus hartingi/lydius, which is known as agricultural pest, was dominant in the diet of Asio otus . When diversity of mammal species within the food composition was examined, Asio otus nesting in forest was found to primarily prefer agricultural and steppe areas, and was also found in woody and bushy areas. The use of Asio otus can be taken into consideration when dealing with rodent species known as agricultural pests.

Potential and Pitfalls of the DNA Metabarcoding Analyses for the Dietary Study of the Large Japanese Wood Mouse Apodemus speciosus on Seto Inland Sea Islands

We assessed the dietary profile of the large Japanese wood mouse (Apodemus speciosus) inhabiting the islands of the Seto Inland Sea and adjacent areas by DNA metabarcoding analyses of feces with the chloroplast trnL (UAA) P6 loop intron region and the mitochondrial cytochrome c oxidase subunit I gene as DNA-barcoding markers. The results indicated that A. speciosus consumed a variety of food items. Fagaceae (Quercus sp.) and Rosaceae were frequently utilized plant families, and the Lepidoptera (Noctuidae) was the frequently utilized animal family. The acorn-producing Quercus species was found to be a fundamental diet, while Rosaceae might be characteristic in temperate regions. The high dependence on the Noctuidae moths as an animal dietary component implies that A. speciosus may be reducing the pest abundance in orchards. Technical pitfalls surrounding the DNA metabarcoding methods for feces of the small rodent were also discussed.

Variation in Local and Systemic Pro-Inflammatory Immune Markers of Wild Wood Mice after Anthelmintic Treatment.

The immune system represents a host’s main defense against infection to parasites and pathogens. In the wild, a host’s response to immune challenges can vary due to physiological condition, demography (age, sex), and coinfection by other parasites or pathogens. These sources of variation, which are intrinsic to natural populations, can significantly impact the strength and type of immune responses elicited after parasite exposure and infection. Importantly, but often neglected, a host’s immune response can also vary within the individual, across tissues and between local and systemic scales. Consequently, how a host responds at each scale may impact its susceptibility to concurrent and subsequent infections. Here we analyzed how characteristics of hosts and their parasite infections drive variation in the pro-inflammatory immune response in wild wood mice (Apodemus sylvaticus) at both the local and systemic scale by experimentally manipulating within-host parasite communities through anthelmintic drug treatment. We measured concentrations of the pro-inflammatory cytokine tumor necrosis factor alpha (TNF-α) produced in vitro in response to a panel of toll-like receptor agonists at the local (mesenteric lymph nodes [MLNs]) and systemic (spleen) scales of individuals naturally infected with two gastrointestinal parasites, the nematode Heligmosomoides polygyrus and the protozoan Eimeria hungaryensis. Anthelmintic-treated mice had a 20-fold lower worm burden compared to control mice, as well as a four-fold higher intensity of the non-drug targeted parasite E. hungaryensis. Anthelmintic treatment differentially impacted levels of TNF-α expression in males and females at the systemic and local scales, with treated males producing higher, and treated females lower, levels of TNF-α, compared to control mice. Also, TNF-α was affected by host age, at the local scale, with MLN cells of young, treated mice producing higher levels of TNF-α than those of old, treated mice. Using complementary, but distinct, measures of inflammation measured across within-host scales allowed us to better assess the wood mouse immune response to changes in parasite infection dynamics after anthelmintic treatment. This same approach could be used to understand helminth infections and responses to parasite control measures in other systems in order to gain a broader view of how variation impacts the immune response.

Serologic survey of the Crimean-Congo haemorrhagic fever virus infection among wild rodents in Hungary

Crimean-Congo haemorrhagic fever virus (CCHFV) is a tick-borne pathogen, which causes an increasing number of severe infections in many parts of Africa, Asia and in Europe. The virus is primarily transmitted by ticks, however, the spectrum of natural hosts regarding CCHFV includes a wide variety of domestic and wild animals. Although the presence of CCHFV was hypothesized in Hungary, data in support of CCHFV prevalence has thus far, proven insufficient. In the present study, rodents belonging to four species, the yellow-necked mouse (Apodemus flavicollis), the striped field mouse (A. agrarius), the wood mouse (A. sylvaticus) and the bank vole (Myodes glareolus), were all systematically trapped in the Mecsek Mountain region (Southwest Hungary), from 2011 through 2013. Rodent sera were collected and screened for CCHFV antibodies with dot-blot pre-screening and immunofluorescence assay. Among the 2085 tested rodents, 20 (0.96%) were positive for IgG antibody against CCHFV. Seroprevalence was the highest (1.25%) in A. flavicollis serum samples. Distinctly, we now provide the first data regarding CCHFV occurrence and seroprevalence among wild rodents in Hungary. This observation represents a need for large-scale surveillance to effectively assess the enzootic background and the potential public health risk of CCHFV in Hungary.

Factors influencing predator roadkills: The availability of prey in road verges

Road mortality is the most noticeable effect of roads on wildlife. Road verges may provide important refuges for small mammals and rabbits, particularly when roads cross intensive agricultural or grazed areas. In these circumstances, the increasing use of verges by prey species may attract predators to road surroundings increasing the risk of roadkill. The aim of this study was to quantify the role of prey availability (small mammals and rabbits) on predator road casualties, taking into account road and surrounding landscape characteristics. We analyzed this effect on different predator species, such as, snakes, owls and mammal carnivores. The study took place in a 10 km stretch of a National Road (EN4) in southern Portugal. Relationships among predator mortality and explanatory variables (prey abundance, landscape characteristics, and road verge features) were evaluated using Multivariate Redundancy Analysis (RDA) followed by a variation partitioning. Our results show that, although landscape features explained most of the mortality variation, the prey availability was also very important. Roadkills of Montpellier snake and Egyptian mongoose are strongly associated with wild rabbit abundance on verges, while mortality of stone marten, barn owl and tawny owl is related with wood mouse abundance, Mediterranean forest (montado) density, and verge shrub density. Implications for verge management and implementation of mitigation actions are discussed. We suggest vegetation removal in verges to decrease shelter and food availability for prey, and/or the promotion of habitat for prey in areas distant from roads.

Unravelling the oxygen isotope signal (δ18O) of rodent teeth from northeastern Iberia, and implications for past climate reconstructions

Small mammals, especially rodents, constitute valuable proxies for continental Quaternary environments at a regional and local scale. Recent studies have demonstrated the relation between the stable oxygen isotope composition of the biogenic phosphate from rodent teeth (δ18Op), and the oxygen isotope composition of meteoric waters (δ18Omw), which is related to air temperatures at mid and high latitudes. This work explores the δ18Op of rodent tooth enamel (from Murinae and Arvicolinae subfamilies) to investigate the palaeoenvironmental conditions in northeastern Iberia during Marine Isotope Stage 3 (MIS 3; ca. 60-30 ka). Fourteen new δ18Op analyses from modern samples in conjunction with forty-six δ18Op analyses previously published are used to decipher the isotope record of present-day rodent teeth in this region. Two main factors should be considered in Iberian palaeoenvironmental reconstructions: the singular nature of Iberian δ18Omw records and the potential seasonality bias of small-mammal accumulation. Methodological proposals are made with a view to ensuring the correct interpretation of the δ18Op of small mammals in reconstructing past air temperatures. This methodology is applied to the MIS 3 sequence of the Cova dels Xaragalls site (Vimbodí-Poblet, Tarragona, Spain), where fifty-one δ18O analyses were performed on wood mouse (Apodemus sylvaticus) lower incisors. A spring-early summer accumulation of small mammals is suggested for the layers at Cova dels Xaragalls. In agreement with previous environmental studies of the site, variations in the δ18Op values suggest slight fluctuations in the climatic conditions throughout the sequence, which are consistent with the stadial-interstadial alternations that characterized MIS 3. Complementary palaeoenvironmental methods determine cooler conditions than nowadays, but within a globally stable climatic period.

Wood mouse feeding effort and decision-making when encountering a restricted unknown food source.

Animals making foraging decisions must balance the energy gained, the time invested, and the influence of key environmental factors. In our work, we examined the effect of predation risk cues and experience on feeding efforts when a novel food resource was made available. To achieve this, we live-trapped wood mouse Apodemus sylvaticus in Monte de Valdelatas (Madrid), where 80 Sherman traps were set in four plots. Traps were subjected to two food-access difficulties in treatments consisting of three consecutive nights: open plastic bottles (easy) and closed bottles (difficult), both using corn as bait. To simulate predation risk, we set fox faeces in half of the traps in each plot. We also considered moonlight (medium/low) as an indirect predation risk cue. We analysed whether bottles had been bitten by mice and the gnawed area of each bottle was measured. Our results indicated that food access difficulty, experience, and predation risk determined mice feeding decisions and efforts. The ability of mice to adapt feeding effort when a new food source is available was demonstrated because a higher proportion of closed bottles exhibited bite marks and the gnawed area was bigger. Moreover, mouse experience was determinant in the use of this new resource since recaptured mice gnawed broader orifices in the bottles and the gnawed area increased each time an individual was recaptured. Additionally, direct predation risk cues prompted mice to bite the bottles whereas the effect of different moon phases varied among the food access treatments. This study provides direct evidence of formidable efficacy of wild mice to exploit a new nutrient resource while considering crucial environmental factors that shape the decision-making procedure.

Late Pleistocene climate change and population dynamics of Japanese Myodes voles inferred from mitochondrial cytochrome b sequences

The Japanese archipelago is comprised of four main islands—Hokkaido, Honshu, Shikoku, and Kyushu—which contain high mountainous areas that likely allowed for lineage differentiation and population genetic structuring during the climatic changes of the late Pleistocene. Here, we assess the historical background of the evolutionary dynamics of herbivorous red-backed voles (Myodes) in Japan, examining the evolutionary trends of mitochondrial cytochrome b gene (Cytb) sequence variation. Four apparent signals from rapid expansion events were detected in three species, M. rufocanus and M. rutilus from Hokkaido and M. smithii from central Honshu. Taken together with results from previous studies on Japanese wood mice (Apodemus spp.), three of the expansion events were considered to be associated with predicted bottleneck events at the marine isotope stage (MIS) 4 period, in which glaciers are thought to have expanded extensively, especially at higher elevations. In the late Pleistocene, the possible candidates are transitions MIS 6/5, MIS 4/3, and MIS 2/1, which can be characterized by the cold periods of the penultimate glacial maximum, MIS 4, and the last glacial maximum, respectively. Our data further reveal the genetic footprints of repeated range expansion and contraction in the northern and southern lineages of the vole species currently found in central Honshu, namely M. andersoni and M. smithii, in response to climatic oscillation during the late Pleistocene. The time-dependent evolutionary rates of the mitochondrial Cytb presented here would provide a possible way for assessing population dynamics of cricetid rodents responding to the late Pleistocene environmental fluctuation.

The role of steroid hormones and individual traits in food intake in the wood mouse (Apodemus sylvaticus).

Availability of food resources affects animal survival and reproduction. Thus, coping with changes in food availability is one of the most crucial behavioural and physiological processes in wildlife. Food intake is a key concept in animal ecology that is directly conditioned by food quality and abundance or diet choice, but may also vary according to individual-related factors (e.g. foraging behaviours, social rank or energy-demanding periods) and the influence of the endocrine system on energy metabolism. Here, we studied food intake in relation to individual characteristics (sex, breeding condition and age) and whether steroid hormones (testosterone and corticosterone metabolites) mediate food intake in wild wood mouse (Apodemus sylvaticus). Field work was carried out in February-March 2014 in Monte de Valdelatas (Madrid, Spain). Wood mice were live-trapped for 10 consecutive days in four independent plots. Traps were baited with 4g of toasted corn and food intake was calculated by subtracting the remaining bait found inside traps. Fresh faecal samples from 130 different wood mice were collected and faecal testosterone and corticosterone metabolites (FTM and FCM, respectively) were analysed by enzyme immunoassays. Food intake was higher in females than males, probably due to greater energy requirements. Non-breeders and young individuals also showed a higher food intake. These individuals usually hold a lower social rank which is associated to limited food resources because of dominants; thus, increased food intake may be a result of freely exploit food bait inside traps while avoiding risky competition. In addition, food intake negatively correlated with FTM levels and positively with FCM levels indicating that both hormones have an active role mediating food intake in the wood mouse. Our data suggest that food intake is a function of both individual traits and the endocrine system that accordingly respond throughout different energy-demanding periods.

Consistent within-group covariance of septal and temporal hippocampal neurogenesis with behavioral phenotypes for exploration and memory retention across wild and laboratory small rodents

Striking differences in the septo-temporal distribution of neurogenesis are found in small rodents. Here, we assessed the association of adult hippocampal neurogenesis with behavioral responses to novelty, temporal and spatial sequence and reversal learning in wild, wild-derived and laboratory rodents using an automated testing apparatus, the IntelliCage. Behaviorally, DBA/2 and wild-derived house mice were quickest to explore a novel environment, wild wood mice and bank voles were slowest, and C57BL/6 intermediate. Rule learning (temporal and spatial) was fastest in wood mice and bank voles, while DBA/2 and house mice performed poorer. C57BL/6 performed similar to the house mice in the temporal task and similar to wild rodents in the spatial task. Using the number of DCX-positive neurons and proliferating, Ki67-positive cells in the septal, intermediate and temporal hippocampus as a proxy, an ANCOVA was used to test for within-group relations between neurogenesis and behavior. We found that higher numbers of DCX-positive cells in the temporal hippocampus were associated with an increased latency and a lower frequency to explore a novel environment. Temporal and spatial sequence learning was not associated with neurogenesis. In the spatial reversal task however, animals with higher septal neurogenesis showed a persevering phenotype and slower re-learning. Our findings provide strong evidence of septo-temporally segregated neurogenesis effects on behavior across five rodent strains and species. While temporal neurogenesis covaries with behavioral responses to novelty, septal neurogenesis relates to perseverance of a successfully learned spatial rule. Importantly, these associations were independent of species or strain and can be found in both wild and domesticated rodents.