Common Small Mammal Research Articles

Validation of hair tubes for small mammal population studies

Survey techniques available to sample mammals have multiplied during the last decades. They offer new opportunities for sampling and monitoring populations, but before widespread use they need to be validated and calibrated to more traditional approaches. We conducted a quantitative assessment of hair tubes designed to monitor common small mammals by comparing results to live-trapping data. Hair tubes are inexpensive, easy to use, and noninvasive, which offers benefits regarding animal ethics. We considered the shape of the tube, application in field conditions, and validated hair-tube results in 3 different habitats based on experimental and field sampling in 2 countries. Tube size selected species entering into the tubes, with shrews detected in small tubes only and rodents in larger tubes. The number of tubes visited (with hair sample) was proportional to the number of individuals captured in live traps. Overall, tubes performed better than traps, detecting individuals where traps did not, making this technique promising for inventory of rare species. The sampling pattern was robust across wood, grassland, and cultivated field habitats and across seasons, which suggests that the proportion of hair tubes visited is a robust indicator of relative abundance of small mammals. In the context of population studies, hair tubes cannot replace trapping because the identification of species or individuals from hair collected in tubes is difficult and costly. We recommend combining hair tubes with livetrapping for increased efficiency and before species identification based on DNA sampling is applied to large-scale population studies.

Genus Apodemus in the Pleistocene of Central Europe: when did the extant taxa appear?

Abstract The extant species of the genus Apodemus represent the most common small mammals of Central Europe. Unfortunately, their phylogenetic past is only poorly known. With the aid of detailed biometric analyses we tried to identify the first appearance of the phenotypic patterns characterizing the extant populations. We examined dental material of Apodemus from 53 community samples from the territory of the Czech Republic and Slovakia dated from the early Villanyian (MN 16/17) to the late Middle Pleistocene (Q 3) with particular respect to their correspondence with the morphometric characteristics of the extant species. While the Toringian (Q 3) interglacial samples invariably include forms identical with the extant taxa A. flavicollis, A. sylvaticus and supposedly A. uralensis (including the items corresponding to A. maastrichtiensis), the samples of Early Pleistocene age (MN 17 – Q 2) exhibited clear differences in the variation pattern which results in questioning the possibility of their co-identification with the respective extant species. In most instances they varied within the limits in resembling A. sylvaticus but exceeded its variation ranges in some non-metric characters. Regarding serious doubts on real taxonomic status of other named fossil species we propose to denote these Plio-Pleistocene sylvaticus-like phenotypes provisionally with the prior name A. atavus Heller, 1936.

SEMICE: An unbiased and powerful monitoring protocol for small mammals in the Mediterranean Region

Schemes to monitor biodiversity change should detect properly target species without harmful effects on individuals and populations, and be powerful enough to detect expected population trends in the face of global change. Targeting is a key aspect of monitoring schemes since there is no single method able to detect unbiasedly all species of any given community, especially the rarest ones. Here we test whether SEMICE (SEguimiento de MIcromamíferos Comunes de España), a monitoring protocol for small mammal biodiversity in the Mediterranean Region, fulfil these requirements. The protocol aims at monitoring common species easy to catch with the two most widely used commercial live traps (18 Sherman and 18 Longworth traps alternated in position across 6×6 trapping grids spaced 15m, brought into operation for three consecutive nights in spring and fall). We used pilot data from twenty-two plots distributed along wide environmental gradients in Catalonia (NE Spain), sampled from 2008 to 2015. The wood mouse (Apodemus sylvaticus) was dominant throughout the study period (992 individuals, 39.0%), followed by the white-toothed shrew (Crocidura russula, 598 individuals, 23.5%) and the Algerian mouse (Mus spretus, 269 individuals, 10.6%). The two most common rodent species experienced strong population declines during the eight-year period (91% for A. sylvaticus and 83% for M. spretus). Regional community data obtained from diet studies of small mammal predators showed that common keystone prey and seed dispersers were sampled properly. No differences among trap types regarding community parameters and similarity indexes, sampling efficiency, detectability, trap-induced mortality, mean size and sex-ratio were detected, confirming previous results for a smaller pilot study. The method was sensitive enough for detecting expected population changes. We recommended extending the SEMICE protocol to sample common keystone small mammals along wide Mediterranean environmental gradients, since the method was sensitive enough to detect, and even test, expected population trends associated to global change for all them.

Intraspecific functional diversity of common species enhances community stability

Common species are fundamental to the structure and function of their communities and may enhance community stability through intraspecific functional diversity (iFD). We measured among‐habitat and within‐habitat iFD (i.e., among‐ and within‐plant community types) of two common small mammal species using stable isotopes and functional trait dendrograms, determined whether iFD was related to short‐term population stability and small mammal community stability, and tested whether spatially explicit trait filters helped explain observed patterns of iFD. Southern red‐backed voles (Myodes gapperi) had greater iFD than deer mice (Peromyscus maniculatus), both among habitats, and within the plant community in which they were most abundant (their “primary habitat”). Peromyscus maniculatus populations across habitats differed significantly between years and declined 78% in deciduous forests, their primary habitat, as did the overall deciduous forest small mammal community. Myodes gapperi populations were stable across habitats and within coniferous forest, their primary habitat, as was the coniferous forest small mammal community. Generalized linear models representing internal trait filters (e.g., competition), which increase within‐habitat type iFD, best explained variation in M. gapperi diet, while models representing internal filters and external filters (e.g., climate), which suppress within‐habitat iFD, best explained P. maniculatus diet. This supports the finding that M. gapperi had higher iFD than P. maniculatus and is consistent with the theory that internal trait filters are associated with higher iFD than external filters. Common species with high iFD can impart a stabilizing influence on their communities, information that can be important for conserving biodiversity under environmental change.

Evaluating camera traps as an alternative to live trapping for estimating the density of snowshoe hares (Lepus americanus) and red squirrels (Tamiasciurus hudsonicus)

Live trapping is one of the methods typically used to estimate population densities of small mammals, but this is labor-intensive and can be stressful to individuals. We assess the use of camera trap hit (detection) rates as a noninvasive alternative to live trapping for estimating population densities of snowshoe hares (Lepus americanus (Erxleben, 1777)) and red squirrels (Tamiasciurus hudsonicus (Erxleben, 1777))—two common small (≤1.5 kg) mammal species in the boreal forests of northern North America. We compared hit rates from camera trapping to live trapping mark-recapture density estimates and asked if the hit window—the length of time used to group consecutive videos together as single detections or “hits”—has an effect on the correlation between hit rates and live trapping density estimates. The relationship between hit rate and population density was sensitive to hit window duration for red squirrels with R 2 values ranging from 0.41 to 0.68, and a 5-min hit window generated the highest value. R 2 values for snowshoe hares ranged from 0.70 to 0.90, and a 10-min hit window generated the highest value, but hares were live trapped and filmed only at very low densities. Our results indicate that camera trapping is a robust means for estimating the density of red squirrels, but the appropriate hit window duration must be determined empirically if camera trapping data are to be used to monitor populations of this species. Additional live trapping and filming of snowshoe hares is required to better assess camera trapping of this species.

Complex demographic responses of a common small mammal to a plant invasion

Context Invasions by non-native plants can alter the abundance and distribution of resources that can affect habitat quality for native animals. Aims We sought to understand the demographic consequences of a plant invasion on a functionally and numerically important rodent in a grassland ecosystem. Specifically, we evaluated how abundance, survival, reproductive activity and population structure of Arizona cotton rats (Sigmodon arizonae) varied across a gradient of invasion by Eragrostis lehmanniana (Lehmann lovegrass), a bunchgrass native to Africa that has invaded grasslands in North America. Methods Over a four-year period, we used capture–recapture methods to survey small mammals on 54 1-ha plots between 10 and 13 times. We used vegetation data collected each autumn to quantify biomass of non-native grass, total biomass and vegetation heterogeneity to characterise vegetation structure on each plot. Key results We captured 1344 individual cotton rats during 106 560 trap-nights across all sampling periods. In areas dominated by non-native grass, abundance of cotton rats increased 7- to 10-fold and survival increased by 117% relative to areas dominated by native grasses. In contrast, reproductive activity of adults decreased by 62% for females and 28% for males, and the proportion of adults in the population decreased by 20% in these same areas. Conclusions Demography of Arizona cotton rats differed markedly in areas invaded by a non-native plant relative to native grasslands, supporting the long-held idea that life histories can reflect local environmental conditions. Because distributions of many non-native plants are predicted to increase in response to future changes in natural and anthropogenic drivers, the potential breadth of these complex effects on communities of native animal is immense. Implications The complex variation in demographic responses across the invasion gradient suggests that it may be necessary to evaluate a suite of vital rates to fully understand the consequences of plant invasions on animals. This is especially important for species of conservation concern because single demographic parameters, which are used frequently as targets to gauge the success of conservation and management activities, could be misleading.

Shippingport, Kentucky, is the type locality for the white-footed mouse,Peromyscus leucopus(Rafinesque, 1818) (Mammalia: Rodentia: Cricetidae)

The white-footed mouse, Musculus leucopus Rafinesque, 1818 (= Peromyscus leucopus), is a common small mammal that is widespread in the eastern and central United States. Its abundance in many habitats renders it ecologically important, and its status as a reservoir for hantavirus and Lyme disease gives the species medical and economic significance. The recognition of two cytotypes and up to 17 morphological subspecies of P. leucopus indicates considerable variation in the species, and to understand this variation, it is important that the nominate subspecies be adequately defined so as to act as a standard for comparison. Relevant to this standard for the white-footed mouse is its type locality, which has generally been accepted to be either the vague “pine barrens of Kentucky” or the mouth of the Ohio River. Newly assembled information regarding the life and travels of Constantine S. Rafinesque, the North American naturalist who described P. leucopus, establishes that Rafinesque observed this species in July 1818 while visiting Shippingport, Kentucky, which is now within the city limits of Louisville, Jefferson Co., Kentucky. Shippingport is therefore the actual type locality for this species.

Towards an Isotope Ecology of Cape Fynbos Small Mammals

We investigated ecological separation through dietary partitioning of small mammals in the nutrient-poor Fynbos biome using a stable isotope approach. Hair samples from eight species of co-occurring small mammals in two separate locations were analysed for stable carbon (13C/12C) and nitrogen (15N/14N) isotope ratios. In addition, we investigated the seasonal variation in diet again by using variation in isotopic composition of one of the most common small mammal species, the Cape spiny mouse. We also analysed seeds and leaves from the most common plant species at each study site. Results showed that some dietary separation exists among these coexisting small mammals. Geographic differences exist in isotope signatures within the Cape spiny mouse, possibly resulting from area-related variations in isotope values of plants, as well as differences in the animals' diets. A. subspinosus hair shows little to no seasonal fluctuation of isotopic signals, except in summer, which possibly indicates a stable diet over much of the year. We conclude that the isotopic approach to determine trophic levels is limited by significant geographic variation in plant isotopes and enrichment in seeds compared to leaves.

Towards an isotope ecology of Cape Fynbos small mammals

We investigated ecological separation through dietary partitioning of small mammals in the nutrient-poor Fynbos biome using a stable isotope approach. Hair samples from eight species of co-occurring small mammals in two separate locations were analysed for stable carbon (13C/12C) and nitrogen (15N/14N) isotope ratios. In addition, we investigated the seasonal variation in diet again by using variation in isotopic composition of one of the most common small mammal species, the Cape spiny mouse. We also analysed seeds and leaves from the most common plant species at each study site. Results showed that some dietary separation exists among these coexisting small mammals. Geographic differences exist in isotope signatures within the Cape spiny mouse, possibly resulting from area-related variations in isotope values of plants, as well as differences in the animals’ diets. A. subspinosus hair shows little to no seasonal fluctuation of isotopic signals, except in summer, which possibly indicates a stable diet over much of the year. We conclude that the isotopic approach to determine trophic levels is limited by significant geographic variation in plant isotopes and enrichment in seeds compared to leaves.

Common vole (Microtus arvalis) ecology and management: implications for risk assessment of plant protection products

Common voles (Microtus arvalis) are common small mammals in some European landscapes. They can be a major rodent pest in European agriculture and they are also a representative generic focal small herbivorous mammal species used in risk assessment for plant protection products. In this paper, common vole population dynamics, habitat and food preferences, pest potential and use of the common vole as a model small wild mammal species in the risk assessment process are reviewed. Common voles are a component of agroecosystems in many parts of Europe, inhabiting agricultural areas (secondary habitats) when the carrying capacity of primary grassland habitats is exceeded. Colonisation of secondary habitats occurs during multiannual outbreaks, when population sizes can exceed 1000 individuals ha(-1) . In such cases, in-crop common vole population control management has been practised to avoid significant crop damage. The species' status as a crop pest, high fecundity, resilience to disturbance and intermittent colonisation of crop habitats are important characteristics that should be reflected in risk assessment. Based on the information provided in the scientific literature, it seems justified to modify elements of the current risk assessment scheme for plant protection products, including the use of realistic food intake rates, reduced assessment factors or the use of alternativee focal rodent species in particular European regions. Some of these adjustments are already being applied in some EU member states. Therefore, it seems reasonable consistently to apply such pragmatic and realistic approaches in risk assessments for plant protection products across the EU.

Small-Mammal Occupancy in Freshwater Marshes of Mandalay National Wildlife Refuge, Louisiana

Small mammals are key consumers in the marsh food web and could serve as indicators of a marsh's potential to support higher-level predators. We studied how small- mammal occupancy varied among plant communities in coastal Louisiana freshwater marshes. We sampled small mammals at 36 sites on 4 different occasions during the late spring in freshwater marshes of the Mandalay National Wildlife Refuge, LA. Mammalian diversity was low; we captured only Oryzomys palustris (Marsh Rice Rats). Occupancy modeling revealed a positive association between Marsh Rice Rat site occupancy and Sagit- taria lancifolia (Bulltongue Arrowhead) biomass. Our data suggest that subtle changes in plant-species composition within a marsh may affect the distribution of the most common small mammal in the ecosystem.

Small-mammal postcrania from the middle Paleocene of Walbeck, Germany

The fissure fills of Walbeck, northwest of Halle, have produced one of the largest known assemblages of Paleocene vertebrates and the only one of this age from Germany. Nearly 6,000 mammalian specimens have been identified, almost half of which represent small mammals of less than 500 g, the majority probably weighing 350 postcranial elements collected more than 70 years ago. Multiple morphs of most of the major limb bones are represented, the most numerous elements being humeri, femora, tibiae, calcanei, and astragali. A small number of bones are attributable to plesiadapiform primates and to the probably euarchontan Adapisoriculidae, both likely to have been arboreal. The vast majority of elements, however, represent terrestrial micro-mammals, some showing semifossorial adaptations but most indicating cursorial or saltatorial locomotion. Most of these bones probably belong to the most common small mammals from Walbeck (based on teeth): Adapisorex, Walbeckodon, and Prolouisina, which have recently been interpreted as stem macroscelideans. The morphology of these bones supports that interpretation. The predominance of terrestrial mammals and the low species diversity of the Walbeck local fauna suggest that it sampled a relatively open and unstable environment.

English

Information on the small mammal communities of the Owabi Wildlife Sanctuary is virtually non-existent despite their role in forest ecosystems. A total of 1,500 trap-nights yielded 121 individuals of rodents and shrews, comprising five species: Praomys tullbergi, Lophuromys sikapusi, Hybomys trivirgatus, Malacomys edwardsi and Crocidura buettikoferi, captured in Sherman traps using 20 × 20 m grids. P. tullbergi was the most common small mammal species in all the four habitat types surveyed, comprising 63.6% of the total number of individual small mammals captured. The Cassia-Triplochiton forest had 61.2% of the entire small mammal individuals captured, and was the only habitat type that harboured higher abundances of the rare small mammal species in the sanctuary (H. trivirgatus and M. edwardsi). It also showed dissimilarity in small mammal species richness and abundance by recording a SÇ¿renson’s similarity index of less than half in comparison with the other three habitat types. Management strategies for the sanctuary should therefore be structured to have minimal impact in terms of development and encroachment on the Cassia-Triplochiton forest area in order to conserve the rare species and biodiversity of the Owabi Wildlife Sanctuary.   Key words: Small mammals, conservation, Ghana, Owabi Wildlife Sanctuary

DIETS OF SMALL MAMMALS IN A SOUTHERN AFRICAN TEMPERATE FOREST

ABSTRACT Diets of the five common small mammal species of the Karkloof Forest, Natal, South Africa, were investigated using stomach content analysis. Rhabdomys pumilio and Mastomys natalensis were omnivorous, though the latter showed a preference for invertebrates. Graphiurus murinus and Myosorex varius were predominantly insectivorous but ate some plant material and fruits. Grammomys dolichurus fed primarily on fruits and plant material although they ate some invertebrates. Seasonal trends in body fat content and the timing of breeding activity of all these species were associated with changes in their diets. Mastomys natalensis ate fruits when these were available in winter, while R. pumilio, M. varius, and G. murinus showed no seasonal increase in fruit consumption. It is suggested that R. pumilio and M. natalensis obtain their energy for breeding primarily from invertebrates, green plant material and flowers. Only Grammomys dolichurus increased its fruit consumption in summer when availability was low...

Palatability of plants to small mammals in nonnative grasslands of east-central Illinois

Understanding the impact of small mammals on the development of grasslands requires information on their food preferences. We conducted feeding trials with 4 species of common small mammals, prairie voles (Microtus ochrogaster), meadow voles (M. pennsylvanicus), white-footed mice (Peromyscus leucopus), and eastern cottontails (Sylvilagus floridanus), to determine the relative palatability of plant shoots and seeds in introduced grasslands of east-central Illinois. Because we needed to conduct many feeding trials we developed a rapid method for comparison of palatability of plants to multiple species of small mammals in the field. We evaluated the method by comparison with previous data on food preference and palatability for voles at nearby study sites. Shoots of herbaceous legumes (Medicago sativa and Trifolium pratense) and dandelions (Taraxacum officianale) were among the most palatable foods for voles, and bluegrass (Poa pratensis) was among the least palatable. Meadow voles found palatable more species of graminoids than did prairie voles, and meadow voles, but not prairie voles, found palatable a greater percentage of graminoids than of forbs. A greater percentage of introduced plants than of native plants were palatable to prairie voles, but this likely reflected a high proportion of introduced graminoids among tested plants. White-footed mice found palatable a few forbs and a greater percentage of annual plants compared with perennial plants, whereas cottontails found palatable many forbs and woody plants and a greater percentage of perennial plants. White-footed mice tended to eat larger amounts and more kinds of seeds than voles, and only white-footed mice tended to eat more of large-seeded species. Plant type did not appear to significantly affect palatability of seeds for any mammal. We used these results to predict the likely impact of small mammals on the development of nonnative grasslands.

Cannibalism of Indian Palm Squirrel (Funambulus palmarum[/i)

The palm squirrel is one of the common small mammals in Sri Lanka and the Indian Palm Squirrel ([i]Funambulus palmarum) is the commonest of all being distributed throughout the island. All palm squirrels are essentially herbivores, however diet varies depending on the species. F. palmarum has a broad, opportunistic diet, consuming a range of foods that vary depending on season. Its diet includes nuts, a range of seeds, fruits, flowers, young shoots, barks, lichens and it occasionally eats insects such as termites and beetles.

Spatio‐temporal patterns of habitat use in voles and shrews modified by density, season and predators

1. Although the intrinsic habitat preferences of a species can be considered to be fixed, the realized habitat use depends on the prevailing abiotic and biotic conditions. Often the core habitats are occupied by dense and stable populations, while marginal habitats become occupied only at times of high density. In a community of interacting species, habitat uses of different species become inter-related, for example an increased density of a strong competitor forcing a weaker competitor to use more marginal habitats. 2. We studied the spatio-temporal distribution patterns of three common small mammal species, the bank vole Myodes glareolus; the field vole Microtus agrestis; and the common shrew Sorex araneus, in a 4-year trapping study carried out on six large islands, each containing a mixture of three main habitat types (forest, field and clear-cut). We experimentally released least weasels (Mustela n. nivalis) to some of the islands to see how the focal species respond to increased predation pressure. 3. Both vole species were largely restricted to their core habitats (bank voles to forests and field voles to fields) at times of low population density. With increasing density, the relative habitat use of both species increased in the clear-cut areas. The common shrew was a generalist in its habitat use at all population densities. 4. The release of the weasels changed the habitat use of all study species. 5. The vole species showed a stronger aggregated pattern than the common shrew, especially at low population density. The vole aggregations remained in the same localities between seasons, except in the case of bank voles after the weasels were released. 6. Bank voles and field voles avoided each other at high density. 7. We conclude that intrinsically differential habitat requirements and flexibility to modify habitat use facilitate the coexistence of the two competing vole species in mosaic landscapes consisting of boreal forests and open habitats.

Can number and size of offspring increase simultaneously? - a central life-history trade-off reconsidered

BackgroundTo maximize their fitness, parents are assumed to allocate their resources optimally between number and size of offspring. Although this fundamental life-history trade-off has been subject to long standing interest, its genetic basis, especially in wild mammals, still remains unresolved. One important reason for this problem is that a large multigenerational pedigree is required to conduct a reliable analysis of this trade-off.ResultsWe used the REML-animal model to estimate genetic parameters for litter size and individual birth size for a common Palearctic small mammal, the bank vole (Myodes glareolus). Even though a phenotypic trade-off between offspring number and size was evident, it was not explained by a genetic trade-off, but rather by negative correlations in permanent and temporary environmental effects. In fact, even positive genetic correlations were estimated between direct genetic effects for offspring number and size indicating that genetic variation in these two traits is not necessarily antagonistic in mammals.ConclusionsOur results have notable implications for the study of the life-history trade-off between offspring number and size in mammals. The estimated genetic correlations suggest that evolution of offspring number and size in polytocous mammals is not constrained by the trade-off caused by antagonistic selection responses per se, but rather by the opposing correlative selection responses in direct and maternal genetic effects for birth size.

Primeros resultados del programa de seguimiento de micromamíferos comunes de España (SEMICE)

We present the results of the first two years of monitoring common small mammals in Spain (SEMICE), developed during 2008 and 2009 in Catalonia and Andorra. The 30 stations (some of them managed by volunteers) are distributed across both the Network of Natural Parks of Barcelona and the Pyrenees, a fact that will provide a reference on small mammal communities in subalpine areas, and allow comparison with those observed in the Mediterranean area. The plots are located across an altitudinal gradient of more than 2,000 m (95-2,255 m.a.s.l.) from typically Mediterranean areas (pine, scrub and oak), through subalpine mountain (scree and meadows), to Eurosiberiane forests (oak and fir). We have used a standardized sampling methodology, consisting of live trapping with Longworth traps in plots of 36 traps spaced 15 meters (0.56 ha). In the Pyrenees we alternated plots with Longworth and Sherman traps to allow the capture of larger species. Throughout the years 2008 and 2009, we captured a total of 1,391 small mammals of 15 species (5 soricidae and 10 rodentia), which represents half of the known species in Catalonia and Andorra. Mammal populations are dominated by Apodemus sp., Crocidura russula, and Mus spretus in the Mediterranean area, and by Myodes glareolus, Apodemus sp. and Eliomys quercinus in the Pyrenees mountains.

A model system for in vitro studies of bank vole borne viruses.

The bank vole (Myodes glareolus) is a common small mammal in Europe and a natural host for several important emerging zoonotic viruses, e.g. Puumala hantavirus (PUUV) that causes hemorrhagic fever with renal syndrome (HFRS). Hantaviruses are known to interfere with several signaling pathways in infected human cells, and HFRS is considered an immune-mediated disease. There is no in vitro-model available for infectious experiments in bank vole cells, nor tools for analyses of bank vole immune activation and responses. Consequently, it is not known if there are any differences in the regulation of virus induced responses in humans compared to natural hosts during infection. We here present an in vitro-model for studies of bank vole borne viruses and their interactions with natural host cell innate immune responses. Bank vole embryonic fibroblasts (VEFs) were isolated and shown to be susceptible for PUUV-infection, including a wild-type PUUV strain (only passaged in bank voles). The significance of VEFs as a model system for bank vole associated viruses was further established by infection studies showing that these cells are also susceptible to tick borne encephalitis, cowpox and Ljungan virus. The genes encoding bank vole IFN-β and Mx2 were partially sequenced and protocols for semi-quantitative RT-PCR were developed. Interestingly, PUUV did not induce an increased IFN-β or Mx2 mRNA expression. Corresponding infections with CPXV and LV induced IFN-β but not Mx2, while TBEV induced both IFN-β and Mx2.In conclusion, VEFs together with protocols developed for detection of bank vole innate immune activation provide valuable tools for future studies of how PUUV and other zoonotic viruses affect cells derived from bank voles compared to human cells. Notably, wild-type PUUV which has been difficult to cultivate in vitro readily infected VEFs, suggesting that embryonic fibroblasts from natural hosts might be valuable for isolation of wild-type hantaviruses.