Seasonal regulation in fluctuating small mammal populations: feedback structure and climate

We studied fluctuating populations of six small mammal species in the Appalachian Plateau of Pennsylvania, USA for 20 yr. We analyzed the feedback structure of these species using statistical time series models for spring and autumn abundances. All species showed a seasonal density-dependent structure, and in five of them first-order feedbacks were dominant in winter and summer. Instead, southern red-backed voles ( Clethrionomys gapperi ) showed a different feedback structure during winter and summer. In three species ( C. gapperi , Napaeozapus insignis and Peromyscus maniculatus ), environmental factors were more important during summer, while the opposite pattern was found in Blarina brevicauda and Tamias striatus . Snowfall influenced positively the winter population growth rates of southern red-backed voles, white-footed mice, woodland jumping mice and eastern chipmunks. We found seasonal differences in the effects of the small mammals assemblage on population growth rates of the two Peromyscus species. The common feedback structure between seasons observed in most of the species, particularly among voles and mice, points to a different feedback structure from northern cyclic small mammals. We conclude that a seasonal feedback structure dominated by intra- and inter-specific competitive interactions may be at the basis of the population dynamics of these species.     

Ectoparasites and other epifaunistic arthropods of sympatric cotton mice and golden mice: comparisons and implications for vector-borne zoonotic diseases

Ectoparasite and epifaunistic arthropod biodiversity and infestation parameters were compared between 2 sympatric small rodent species, the cotton mouse (Peromyscus gossypinus (Le Conte)) and golden mouse (Ochrotomys nuttalli (Harlan)), in southern Georgia from 1992 to 2003. Because the cotton mouse is known to be a reservoir of more vector-borne zoonotic pathogens than the golden mouse, we hypothesized that it would be parasitized by more ectoparasites that are known to be vectors of these pathogens. Cotton mice (n = 202) were parasitized by 19 species of arthropods, whereas golden mice (n = 46) were parasitized by 12 species. Eleven species of arthropods were recovered from both host species, whereas 7 were recorded only from cotton mice, and 1 species only from golden mice. Infestation prevalences (percent of mice parasitized) were significantly higher for 1 species of arthropod (the tropical rat mite Ornithonyssus bacoti (Hirst)) infesting cotton mice and for 4 species (the flea Peromyscopsylla scotti Fox and the mites Glycyphagus hypudaei Koch, Androlaelaps casalis (Berlese), and Androlaelaps fahrenholzi (Berlese)) infesting golden mice. Mean intensities (mean per infested mouse) were significantly higher for 2 species (the flea Orchopeas leucopus (Baker) and the blacklegged tick Ixodes scapularis Say) infesting cotton mice and for 2 species (G. hypudaei and A. fahrenholzi) infesting golden mice. Ectoparasites that are known to be vectors of zoonotic pathogens were significantly more common on cotton mice than on golden mice. These ectoparasites included the rhopalopsyllid flea Polygenis gwyni (Fox), a vector of the agent of murine typhus; I. scapularis, the principal vector of the agents of Lyme borreliosis, human granulocytic ehrlichiosis, and human babesiosis; and O. bacoti, a laboratory vector of several zoonotic pathogens. However, 2 species of ixodid ticks that can transmit zoonotic pathogens were recovered from both host species. These were the American dog tick Dermacentor variabilis (Say), the principal vector of the agent of Rocky Mountain spotted fever in eastern North America, and Ixodes minor Neumann, an enzootic vector of the agent of Lyme borreliosis. Overall, the cotton mouse was parasitized by significantly more ectoparasites that are known to be vectors of zoonotic pathogens than was the golden mouse. These data support the hypothesis that the cotton mouse has greater epidemiological importance for zoonotic vector-borne pathogen transmission than does the golden mouse.     

Serosurvey of wild rodents for hantaviruses in Panama, 2000-2002

Five hundred fifty-six samples representing 24 species of small mammals (two species of marsupials and 22 rodents) were collected in Panama between February 2000 and July 2002. The samples were examined for antibodies to hantaviruses by means of enzyme-linked immunosorbent assay or immunoblot assays. The serologic results indicated that several rodent species might act as hantaviral reservoirs in Panama: Costa Rican pygmy rice rat (Oligoryzomys fulvescens costaricensis), four positive of 72 tested (5.6%); Cherrie's cane rat (Zygodontomys brevicauda cherriei), five of 108 (4.6%); Mexican deer mouse (Peromyscus mexicanus), one of 22 (5%); Mexican harvest mouse (Reithrodontomys mexicanus), one of seven (14%); Chiriquí harvest mouse (Reithrodontomys creper), one of two (50%); and Sumichrast's harvest mouse (Reithrodontomys sumichrasti), three of four (75%). Hantavirus infection in Peromyscus mexicanus and the three species of Reithrodontomys was caused by Rio Segundo hantavirus, a species of virus not previously reported from Panama. At least three hantaviruses, therefore, are known to infect populations of wild rodents in the country. However, given the total number of animals tested, the role of these rodent species in the epidemiology and epizootiology of hantavirus infections remains unclear.     

On the structure of rodent communities in tropical forests of southern Vietnam

The abundance, species diversity, and spatial distribution of small mammals were studied in two localities in southern Vietnam: the Cat Tien National Park and the Binh Chau Nature Reserve. Rodents were trapped on the ground and in the tropical forest canopy (2–12 m above the ground), marked, and released on the spot. Species diversity of small mammals in undisturbed tropical forest (9 species) was higher than in disturbed tropical forest (14 species). The rat Maxomys surifer and the squirrel Callosciurus flavimanus were dominant. In undisturbed forest, the frequencies of rodent occurrence on the ground and in the canopy were of the same order; in disturbed forest, rodents occurred in the canopy an order of magnitude less frequently than on the ground.     

Leaf phenology in relation to canopy closure in southern Appalachian trees

Leaf phenology varies markedly across tree species of temperate deciduous forests. Early leafing in spring may increase light capture and carbon gain prior to canopy closure, allowing saplings to survive in understory sites deeply shaded in midsummer. We quantified sapling leaf phenology for 18 tree species and seasonal variation in understory light availability at three sites along a ridge-slope-cove landform gradient in the Great Smoky Mountains National Park. Early leafing species (e.g., Aesculus flava, Carpinus caroliniana) broke bud an average of 24 d before late leafers (e.g., Magnolia fraseri, Nyssa sylvatica). Canopy closure occurred 14-18 d earlier and summer understory light was on average 63-74% lower on intermediate and mesic sites than on the xeric site. Early leafing species intercepted 45-80% of their growing season photon flux before canopy closure vs. 8-15% for late leafers. However, earlier leafing increased exposure to freezing temperatures by 5.5% per week near the mean time of bud break. Early leafing is strongly correlated with midsummer shade, risk of freezing temperatures, and distribution on mesic sites across a "main spectrum" of 15 deciduous species. Differences in leaf phenology and resultant impacts on spring carbon gain may help determine tree shade tolerance and distribution in southern Appalachian forests.     

Maximizing survivorship in cold: thermogenic profiles of non-hibernating mammals

Winter-active small mammals residing in seasonal environments employ many different behavioral, anatomical and physiological mechanisms to cope with cold. Herein we review research on survival mechanisms in cold employed by small mammals with emphasis on the families Soricidae, Muridae and Sciuridae. The focus of this review is on research delineating the role of seasonal changes in resting metabolic rate (RMR), nonshivering thermogenesis (NST), body mass, and communal nesting in enhancing winter survivorship of six species of small mammals (masked shrewSorex cinereus, short-tailed shrewBlarina brevicauda, southern red-backed voleClethrionomys gapperi, white-footed mousePeromyscus leucopus, deer mouseP. maniculatus, and southern flying squirrelGlaucomys volans) residing in the Appalachian Mountains of Pennsylvania, USA. Each species shows good over-winter survivorship but exhibits a different suite of mechanisms to maximize survival in cold.B. brevicauda, S. cinereus, andG. volans show slight increases in RMR during winter, whereasPeromyscus andC. gapperi exhibit decreased RMR overwinter. All six species experience elevated NST in winter. The comparatively low RMR and NST ofG. volans during winter was attributable to a decreased energy expenditure due to a larger body mass, coupled with communal nesting in cavities of trees that provided insulation from low ambient temperatures. Squirrels nesting singly experienced a longer period of elevated NST in winter and higher mean NST year-round than did squirrels nesting communally. Energy conservation in the form of growth retardation in winter was exhibited byC. gapperi andS. cinereus but not the other species.     

Human activity and habitat type affect perceived predation risk in urban white‐footed mice (Peromyscus leucopus)

Predation risk is one of the largest costs associated with foraging in small mammals. Small mammals select microhabitat features such as tree and shrub canopy cover, woody debris and vegetative ground cover that can lower the risk of detection from predators and provide greater protection if discovered. Small mammals also increase foraging activity and decrease selection for cover when cloud cover increases and moon illumination is less. Often researchers assume small mammals in urban areas respond to these cues in the same manner as in natural areas, but these cues themselves are altered in urban zones. In this study, we investigated how Amur honeysuckle (Lonicera maackii) and coarse woody debris (CWD) affected giving‐up density (GUD) in white‐footed mice (Peromyscus leucopus). Each of three habitat treatments (open flood channel, the edge and interior of the honeysuckle patch) contained cover treatments with coarse woody debris present or absent. The six treatment combinations were compared to environmental variables (temperature, humidity and illumination) and habitat variables to test their effect on GUD. Peromyscus leucopus foraged to lower densities in areas with CWD present and also under the honeysuckle canopy, using this invasive shrub to decrease predation risk, potentially increasing survivability within this urban park. Increased human presence negatively affected foraging behavior across treatments. Human presence and light pollution significantly influenced P. leucopus, modifying their foraging behavior and demonstrating that both fine‐ and coarse‐scale urban factors can affect small mammals. Foraging increased as humidity increased, particularly under the honeysuckle canopy. Changes in illumination due to moonlight and cloud cover did not affect foraging behavior, suggesting urban light pollution may have altered behavioral responses to changes in light levels. Lonicera maackii seemed to facilitate foraging in P. leucopus, even though it adversely affects the plant community, suggesting that its impact may not be entirely negative.     

Disparate distribution patterns between canopy and subcanopy life-forms in two temperate North American forests

Quantitative vegetational data of canopy and woody subcanopy species (two life-forms adapted to occupy different strata at maturity) were compared with data collected in two temperate forest ecosystems to determine whether they exhibit a similar pattern of distribution. Tidal freshwater swamps (21 stands) and southern Appalachian forests (19 stands) were examined from data obtained using identical sampling methods. Separate structural analyses of the canopy, sapling, and subcanopy species were compared using the indirect ordination algorithm Detrended Correspondence Analysis. Environmental measurements collected in each stand were assessed for their relationship to the distribution of stands depicted by the ordination diagrams.Canopy trees and saplings showed a similar pattern of distribution, suggesting that the resource requirements of saplings and canopy-statured adults are similar. In contrast, the subcanopy species (species genetically adapted to an understory existence, i.e., shrubs and small understory trees) of neither ecosystem showed any discernable distributional relationship to the canopy or sapling layers (in tidal swamps, there was no clear way to even segregate subcanopy stands into communities). Environmental gradients associated with the subcanopy ordinations differed from those of the canopy and sapling strata in both forest systems, suggesting that subcanopy species partition different resources than do canopy species.If a lack of similarity in distribution patterns between canopy and subcanopy species is universal in temperate forests, then the common practice of combining sapling and subcanopy species in structural analyses may hinder our understanding of subcanopy structural patterns in forests.     

唐家河自然保护区高山姬鼠和中华姬鼠夏季生境选择的比较

为揭示影响高山姬鼠和中华姬鼠夏季空间分布的生态因素,采用样线法和样方取样法,于2009年6—8月在四川省唐家河国家级自然保护区内对两种姬鼠的生境选择进行了比较研究。结果表明:两种姬鼠主要利用坡度平缓,郁闭度、落叶层盖度、乔木胸径和高度较小,灌木、竹子和草本密度适中而草本盖度较大的生境;高山姬鼠频繁出现在海拔较低(1400 m左右)、草本植物较大(平均高度为16—30 cm)的生境中,而中华姬鼠频繁出现在海拔较高(1900 m左右)、草本植物较小(平均高度<15 cm)的生境中。此外,高山姬鼠频繁出现在竹林较矮(平均高度<1 m)、水源距离较近(<50 m)、植被演替阶段较低(小树林)的常绿-落叶阔叶混交林中,而中华姬鼠对这4种生态因子无明显的选择性。两种姬鼠在对生境的利用上虽具一定重叠性,但对诸多生境变量选择上的差异表明各自具有不同的生境利用模式。海拔、植被演替阶段、郁闭度和草本高度4个生境变量判别函数系数的绝对值明显大于其他变量,表明高山姬鼠和中华姬鼠在生境上的分割可能主要与这4个变量有关。生境利用模式的不同有助于两种姬鼠同域共存。     

Comparative analysis of testis protein evolution in rodents

Genes expressed in testes are critical to male reproductive success, affecting spermatogenesis, sperm competition, and sperm-egg interaction. Comparing the evolution of testis proteins at different taxonomic levels can reveal which genes and functional classes are targets of natural and sexual selection and whether the same genes are targets among taxa. Here we examine the evolution of testis-expressed proteins at different levels of divergence among three rodents, mouse (Mus musculus), rat (Rattus norvegicus), and deer mouse (Peromyscus maniculatus), to identify rapidly evolving genes. Comparison of expressed sequence tags (ESTs) from testes suggests that proteins with testis-specific expression evolve more rapidly on average than proteins with maximal expression in other tissues. Genes with the highest rates of evolution have a variety of functional roles including signal transduction, DNA binding, and egg-sperm interaction. Most of these rapidly evolving genes have not been identified previously as targets of selection in comparisons among more divergent mammals. To determine if these genes are evolving rapidly among closely related species, we sequenced 11 of these genes in six Peromyscus species and found evidence for positive selection in five of them. Together, these results demonstrate rapid evolution of functionally diverse testis-expressed proteins in rodents, including the identification of amino acids under lineage-specific selection in Peromyscus. Evidence for positive selection among closely related species suggests that changes in these proteins may have consequences for reproductive isolation.     

Regeneration dynamics of Tsuga canadensis in the southern Appalachian Mountains, USA

Tsuga canadensis is often considered a foundation species because of its influence on the biological and ecological processes of upland forest systems. With hemlock woolly adelgid (Adelges tsugae; HWA)-induced mortality of T. canadensis in southern Appalachian upland forests, there is a crucial need to understand the regeneration dynamics of this tree species. This research was conducted within mature T. canadensis forests of Great Smoky Mountains National Park (GSMNP) prior to widespread HWA infestation. Tsuga canadensis regeneration abundance is lower than has been reported in more northern locales, but varies widely among sites in the southern Appalachian Mountains. Ordination results suggest landscape-scale patterns of regeneration abundance that are influenced by gradients in understory Rhododendron maximum cover, soil sand and nutrient content. Regression models reinforce the observed gradients in regeneration abundance. Sites with abundant T. canadensis regeneration have less R. maximum cover, soil sand and litter depth, but more soil nutrient availability. Tsuga canadensis seedlings and saplings tend to be spatially aggregated at the 14 × 21 m plot scale. Sites with spatially aggregated seedlings and saplings have greater canopy openness and more species with gap affinity. This research elucidates associations between successful T. canadensis regeneration and site factors such as soil nutrient availability and canopy dynamics. More forest surveys are required to understand the conditions necessary for successful T. canadensis regeneration. Land managers involved in forest restoration efforts may have to utilize appropriate silvicultural techniques conjoined with R. maximum removal operations to regenerate T. canadensis in southern Appalachian upland forests.     

Low clouds and cloud immersion enhance photosynthesis in understory species of a southern Appalachian spruce-fir forest (USA)

High-altitude forests of the southern Appalachian Mountains (USA) are frequently immersed in clouds, as are many mountain forests. They may be particularly sensitive to predicted increases in cloud base altitude with global warming. However, few studies have addressed the impacts of immersion on incident sunlight and photosynthesis. Understory sunlight (photosynthetically active radiation, PAR) was measured during clear, low cloud, and cloud-immersed conditions at Mount Mitchell and Roan Mountain, NC (USA) along with accompanying photosynthesis in four representative understory species. Understory PAR was substantially less variable on immersed vs. clear days. Photosynthesis became light-saturated between ～100 and 400 μmol · m(-2) · s(-1) PAR for all species measured, corresponding closely to the sunlight environment measured during immersion. Estimated daily carbon gain was 26% greater on clear days at a more open canopy site but was 22% greater on immersed/cloudy days at a more closed canopy site. F(v)/F(m) (maximum photosystem II efficiency) in Abies fraseri seedlings exposed to 2.5 min full sunlight was significantly reduced (10%), indicating potential reductions in photosynthesis on clear days. In addition, photosynthesis in microsites with canopy cover was nearly 3-fold greater under immersed (2.6 mmol · m(-2) · h(-1)) vs. clear conditions (0.9 mmol · m(-2) · h(-1)). Thus, cloud immersion provided more constant PAR regimes that enhanced photosynthesis, especially in shaded microsites. Future studies are needed to predict the survival of these refugial forests under potential changes in cloud regimes.     

Hemlock woolly adelgid invasion affects microhabitat characteristics and small mammal communities

Hemlock woolly adelgid (HWA) invasion and preemptive logging practices alter the habitat structure of New England forests and may indirectly affect associated small mammal communities. Microhabitat structure was measured and small mammals were censused in eight large experimental plots to quantify these effects. The Harvard Forest long-term ecological research experiment is a replicated two-block design that includes four ~ 0.81-ha canopy treatments: (1) hemlock control, (2) hardwood control, (3) girdled Treatment, in which hemlock trees were killed by girdling in 2005 and left standing to simulate HWA invasion, and (4) logged treatment, in which trees were removed to simulate preemptive logging management practices. Nine microhabitat characteristics were measured from plot photos revealing differences among ground and canopy microhabitat structure. Small mammals were censused during high (2012) and low (2013) abundant years. Populations of common species were estimated with mark-recapture analysis. Peromyscus spp. were not affected by treatment in either year, but southern red-backed vole populations were greatest in the girdled treatments in 2012 and rarely captured in 2013. Between 6 and 9 mammal species were recorded in all treatments and species composition varied slightly. Estimated species richness was greater in girdled treatments than hemlock controls, but did not differ between girdled and logged treatments, which suggests preemptive logging is as detrimental to some small mammal species as HWA invasion. Overall, there is little evidence of a major shift in small mammal community structure in response to HWA invasion, with only minor changes in relative abundance both years.     

Long-term responses in population dynamics and diversity of small mammals in riparian and upland habitats within an agricultural landscape

Riparian zones in agricultural landscapes provide linear non-crop habitats for a variety of plant and mammal species, and hence are an important component of biodiversity. To date, variable responses of abundance, species richness, and species diversity of small mammals have been recorded in riparian and upland habitats. To address this variability, we provide a detailed analysis of seasonal changes in abundance and diversity of terrestrial small-mammal communities over a 7-year period within an agricultural landscape in south-central British Columbia, Canada. We tested the hypotheses (H) that abundance, species richness, and species diversity of communities of small mammals (H₁), and demographic parameters of reproduction, recruitment, and survival of the major species: deer mouse (Peromyscus maniculatus) and montane vole (Microtus montanus) (H₂), would be higher in riparian than upland habitats. Mean total abundance of small mammals was higher in summer and winter, and species richness higher in summer, in riparian than hedgerow habitats. Winter population data supported the total and species abundance patterns for small mammals, but species richness was similar, and diversity lower, in riparian than hedgerow sites during winter periods. Deer mice were the dominant species in terms of abundance and reproductive output for pregnancies and recruitment, but not survival, in riparian sites. Montane voles were similar in abundance and demographic parameters in the two habitats. House mice (Mus musculus) preferred hedgerows and wandering shrews (Sorex vagrans) riparian sites. Demographic parameters for deer mice and montane voles indicated that both riparian and hedgerow sites were “source” rather than “sink” habitats, and likely contribute to maintenance of mammal diversity in agricultural landscapes.     

Response to enrichment, type and timing: small mammals vary in their response to a springtime cicada but not a carbohydrate pulse

1. Masting events in the autumn provide a carbohydrate-rich pulse of resources that can influence the dynamics of small mammals and their natural enemies. Similar patterns are observed with the periodical cicada emergence which provides a protein-rich pulse in the spring, but comparisons are confounded by timing and food type. 2. We compared the influence of a naturally occurring spring pulse of cicadas with an experimental spring pulse of carbohydrate-rich seeds. We used a replicated population level field experiment and capture-mark-recapture techniques to record the vital rates, demographics, and abundance of Peromyscus leucopus (the white-footed mouse), as well as other small mammals and their parasites. 3. The density of P. leucopus on grids where cicadas emerged was 55% higher than controls as a consequence of early breeding. This was followed by an increase in the prevalence of the nematode Pterygodermatities peromysci, reduced breeding and decreased recruitment rates. Other small mammals including Tamias striatus (eastern chipmunk) and Blarina brevicauda (short-tailed shrew), increased in density, but there was no affect on Sorex cinereus (masked shrew). 4. In contrast to the presence of cicadas, there was no influence of sunflower seed supplementation on small mammal density, vital rates, or reproduction with the exception of an increase in B. brevicauda density. The response of small mammals to seasonal pulses depends on timing, food type, and species.     

Niche expansion after competitor extinction? A comparative assessment of habitat generalists and specialists in the tree floras of south‐eastern North America and south‐eastern Europe

Aim The aim of this study was to test R.H. MacArthur’s hypothesis that realized niche breadth is constrained by species pool size – the greater the number of species in a region, the more competition restricts the distribution of each species with respect to environmental tolerances and habitat characteristics. Location The northern Balkan region in south‐eastern Europe (Illyrian Floristic Province) and the southern Appalachian region of the USA. Methods We compared co‐occurrence‐based distributions of habitat specialization of tree species in two geographic regions that are ecologically similar but differ in species pool size. We applied two methods. First, we used a rank‐ordering of species along a gradient of estimated niche breadth that is based solely on species co‐occurrence information derived from vegetation databases from each region. To compare niche‐breadth distributions of different datasets we developed a procedure that standardizes expected values of species co‐occurrences independently of the size of the species pool. Second, we calculated species turnover along an elevational gradient for both regions, estimated as the rate of decay of compositional similarity with elevation distance. Results Despite a twofold larger species pool, and in contrast to our hypothesis, there was no greater specialization trend in the tree species of the southern Appalachian region, regardless of phylogenetic subgroupings or whether rare species were included. After correcting for differences in species pools, the similarity decay with elevation distance was marginally stronger in the southern Appalachian region. Main conclusions MacArthur’s hypothesis was not supported by our analysis. While the compositional distance decay with elevation revealed only a slight trend towards narrower realized niches in the tree flora of the southern Appalachian region, the co‐occurrence approach suggested the opposite. Our results indicate that species distributions are largely constrained by environmental tolerances, and that biotic pressure in the form of competition from ecologically similar species plays a relatively minor role in the ability of species to establish mature individuals in different habitat types.     

Pneumocystosis in wild small mammals from California

Cyst forms of the opportunistic fungal parasite Pneumocystis carinii were found in the lungs of 34% of the desert shrew, Notiosorex crawfordi (n = 59), 13% of the ornate shrew, Sorex ornatus (n = 55), 6% of the dusky-footed wood rat, Neotoma fuscipes (n = 16), 2.5% of the California meadow vole, Microtus californicus (n = 40), and 50% of the California pocket mouse, Chaetodipus californicus (n = 2) caught from southern California between February 1998 and February 2000. Cysts were not found in any of the harvest mouse, Reithrodontomys megalotis (n = 21), California mouse, Peromyscus californicus (n = 20), brush mouse, Peromyscus boylii (n = 7) or deer mouse, Peromyscus maniculatus (n = 4) examined. All infections were mild; extrapulmonary infections were not observed. Other lung parasites detected were Hepatozoon sp./spp. from M. californicus and Notiosorex crawfordi, Chrysosporium sp. (Emmonsia) from M. californicus, and a nematode from S. ornatus.     

Application of molecular methods to identify food resources of short-eared owl (Asio flammeus) in wetland community

The short-eared owl (Asia flammeus), which lives in open wetland habitats, has been threatened and become endangered in South Korea due to the destruction and loss of its habitats. However, the diet of the short-eared owl remains to be studied. The prey of the short-eared owl was monitored using molecular methods as an alternative tool. A total of 121 pellets of the species were collected in the Dalsung wetland. Of these pellets, about 30% (n = 33) were selected for prey identification in 2002 (n = 12), 2003 (n = 6) and 2006 (n = 15). Two hundred and thirty-two bone fragments were successfully analyzed and 9 prey species were detected. In an expanded analysis, excluding 4 pellets used for the preliminary analysis, small mammals constituted the highest percentage (89.1%): 47.6% Eurasian field mouse (Apodemus agrarius); 27.2% European harvest mouse (Micromys minutus); 6.1% Japanese wild house mouse (Mus musculus); 5.4% Asian lesser white-toothed shrew (Crocidura shantungensis); and 2.7% Norway rat (Battus norvegicus). Not only small mammals, but birds and amphibians were also identified: 4.1% Japanese quail (Cotumix japonica); 3.4% vinous-throated parrotbill (Paradoxornis webbianus); 0.7% eastern turtle dove (Streptopelia orientalis); and 2.7% Kori salamander (Hynobius yangi). This result would be valuable in understanding the feeding ecology of the short-eared owl in its wetland habitats.     

Implications of raccoon latrines in the epizootiology of baylisascariasis.

Raccoons (Procyon lotor) frequently establish defecation sites, termed latrines, on large logs, stumps, rocks, and other horizontally oriented structures/surfaces. These latrines are important foci of infective eggs of Baylisascaris procyonis, a nematode parasite of raccoons which is pathogenic to numerous species of mammals and birds. To examine the role of raccoon latrines in this animal-parasite interaction, we documented animal visitations to raccoon latrines in two large forested tracts and two woodlots in Indiana (USA) during 1994 and 1995. Species richness of vertebrate visitors did not differ between sites or years, but species composition differed by site and year. Fourteen mammal and 15 bird species were documented visiting raccoon latrines. Small granivorous mammals, including white-footed mice (Peromyscus leucopus), eastern chipmunks (Tamias striatus), and tree squirrels (Sciurus carolinensis, S. niger, Tamiasciurus hudsonicus) were the most common visitors to latrine sites. White-footed mice, chipmunks, white-breasted nuthatches (Sitta carolinensis), and opossums (Didelphis virginiana) were photographed foraging on undigested seeds in raccoon feces. Active foraging at latrines also was shown experimentally; seeds embedded in raccoon feces were removed at a greater rate at latrine sites than at nonlatrines. We conclude that raccoon latrines are visited routinely by a variety of vertebrates, especially small granivorous rodents and birds which forage for seeds in raccoon feces, and that raccoon latrines are probable sites of transmission of B. procyonis to susceptible mammals and birds.     

Influence of habitat characteristics on small mammals in a Mexican high-altitude grassland

Small mammals in a high-altitude grassland area close to Mexico City were studied. Populations of 10 species were censused using live traps in 48 sample quadrats. Within each quadrat, vegetation characterization, including complete floristic listings, cover values for species and layers and values of habitat modification, were assessed. Habitats were described according to plant communities identified using ordination and classification methods. Nine different plant communities were obtained. Densities and abundance of all small mammal species were calculated for each of the habitats classified. Peromyscus alsloni was the most abundant species in all habitats, reaching maximum densities of 55 ha⁻¹ in pine forest with dense ground and herb layer. Peromyscus melanotis also occurred in all habitats but at lower densities (maximum 29 ha⁻¹). Reithrodontomys megalotis was found in all habitats except in tall dense grassland. Densities for this species were generally low (1-9 ha⁻¹) but reached 19 ha⁻¹ in short dense grassland. All other species were largely absent from 4–8 habitats and showed very low densities (0.75–4 ha⁻¹). The densities of the more abundant species were largely correlated with more open habitats and higher indices of habitat modification. Lower altitude grassland habitats have a greater abundance of small mammals and a higher species richness than the medium and higher altitude, physiognomically more complex habitats. Species richness was highest in tall pine-alder forest with a species-rich, dense herb layer and lowest in pine forest with dense ground and herb layers. Species richness was positively correlated with overall small mammal density.