Small Mammal Species Richness Research Articles

Dust as a contributor to the road-effect zone: a case study from a minor forest road in Australia

The road-effect zone is a concept developed to describe the impact of influences such as noise, vibration, light and dust associated with roads and traffic on the surrounding area. Although many aspects associated with the road-effect zone have been investigated, the influence of dust remains poorly understood. Gap Creek Road, a minor road traversing forest near Brisbane, Australia, was upgraded in 2010 by sealing and realignment. The present study compares pre- and post-construction dust levels within the forest, and the diversity and abundance of ground-dwelling mammals near (2–5 m) and far (80–100 m) from the road. Prior to the upgrade, dust levels were very high with deposition rates equivalent to a major daily dust storm. The key influence of the upgrade was the almost complete elimination of this dust production; hence, we predicted that species richness and abundance of small mammals near the road would increase significantly after the upgrade. Pre-upgrade surveys confirmed that the forest supported a diverse and abundant community of ground-dwelling mammal species with eight species detected, including in highly dust-affected sites near the road. Following the upgrade, there was little change in the abundance of species, though some were significantly more abundant away from the road. These results suggest that, in certain environments, dust may have far less impact on ground-dwelling mammals than expected.

Influence of Human Disturbance to the Small Mammal Communities in the Forests

Small mammals have been proposed playing an important role in the energy flow and regeneration of forest ecosystems. We compared species richness, diversity (H’) of small mammal communities and abundance of six dominant species of small mammals in disturbed and protected forests (four age classes: 6 - 10, 11 - 15, 16 - 20 and 31 - 40 years old) in China. We also investigated the structural variables (such as species richness, cover rate and abundance of shrubs and grasses) in the bottom layer, which considered to be important for small mammals and might be altered by human disturbance. The relationships between small mammals and these structural variables were examined to determine the potential effects of human disturbance on the small mammals in the restored forests. Our results indicated that the structure and composition of the vegetation in the bottom layer were simplified by human disturbance, while the abundance and cover rate of grasses were significantly increased. Although no significant differences were observed in species richness of small mammals between the protected and disturbed forests at the same age, the diversity index of small mammals in the protected forests was always significantly higher than in the disturbed forests. Regression showed that the species richness and diversity of small mammals increased with the species richness of shrubs, and was negatively correlated to the cover rate of grasses in the bottom layer. Human disturbance increased the total abundance of small mammals, and the increased cover rate of grasses in the bottom layer was beneficial to the abundance of small mammals. Obvious succession of small mammal communities occurred as the protected forest aged. In the protected forests, small ground-dwelling mammals (A. chevrieri, E. miletus and M. pahari) were the dominant species in the younger forests. Other mammals (T. belangeri, D. pernyi and C. erythraeus) gradually became the dominant species as the protected forests aged. However, in the disturbed forests, the smaller ground-dwelling mammals (T. belangeri, D. pernyi and C. erythraeus) were always the dominant species at all ages of the disturbed forests. Regression indicated that the cover rate of grasses in the bottom layer was beneficial to the three smaller body size and ground-dwelling small mammal species, while the shrubs were beneficial to the three bigger body size mammal species.

Biological Control of Saltcedar (Tamarixspp.) by Saltcedar Leaf Beetles (Diorhabdaspp.): Effects on Small Mammals

Abstract. The spread of introduced saltcedar (Tamarix spp.) throughout many riparian systems across the western United States motivated the introduction of saltcedar leaf beetles (Diorhabda carinulata, D. elongata; Chrysomelidae) as a biological control agent specific to saltcedar. I monitored small mammal populations for up to 12 years as saltcedar defoliation progressed at 3 of the original saltcedar beetle release sites and at an additional site where beetles established through dispersal. There was no evidence of any linear effect of increasing defoliation over time on small mammal species richness. Estimated population sizes of 4 small mammal species, based on mark-release-recapture trapping, showed linear responses to saltcedar defoliation at particular sites, but all of these species were represented by only 3 years of data at those sites. Increases in the abundance of 2 species of desert-adapted heteromyid rodents, Merriam's kangaroo rat (Dipodomys merriami) and Panamint kangaroo rat (D. panaminti...

Predicting small mammal and flea abundance using landform and soil properties in a plague endemic area in Lushoto District, Tanzania.

Small mammals particularly rodents, are considered the primary natural hosts of plague. Literature suggests that plague persistence in natural foci has a root cause in soils. The objective of this study was to investigate the relationship between on the one hand landforms and associated soil properties, and on the other hand small mammals and fleas in West Usambara Mountains in Tanzania, a plague endemic area. Standard field survey methods coupled with Geographical Information System (GIS) technique were used to examine landform and soils characteristics. Soil samples were analysed in the laboratory for physico-chemical properties. Small mammals were trapped on pre-established landform positions and identified to genus/species level. Fleas were removed from the trapped small mammals and counted. Exploration of landform and soil data was done using ArcGIS Toolbox functions and descriptive statistical analysis. The relationships between landforms, soils, small mammals and fleas were established by generalised linear regression model (GLM) operated in R statistics software. Results show that landforms and soils influence the abundance of small mammals and fleas and their spatial distribution. The abundance of small mammals and fleas increased with increase in elevation. Small mammal species richness also increases with elevation. A landform-soil model shows that available phosphorus, slope aspect and elevation were statistically significant predictors explaining richness and abundance of small mammals. Fleas' abundance and spatial distribution were influenced by hill-shade, available phosphorus and base saturation. The study suggests that landforms and soils have a strong influence on the richness and evenness of small mammals and their fleas' abundance hence could be used to explain plague dynamics in the area.

Patrones de distribución de micromamíferos en gradientes altitudinales del noroeste Argentino

We describe the altitudinal variation in species richness, turnover and species composition of small mammals through field surveys along 4 transects ranging from tropical rainforests at 500m to high Andean deserts at 4 000m in northwestern Argentina. The elevation pattern of richness for all small mammals decreases with altitude, mainly due to the high diversity of bats in the lowlands. For the terrestrial small mammals there was a clear curvilinear pattern of richness with a peak near the upper tree line at 2 700m. The maximum values of the species turnover rates were located in the upper part of the gradient at 3 500m. The composition of small mammals communities in every single elevation transect was consistent with the phytogeographic scheme, with species characteristics of montane rainforest, temperate cloud forests and high Andean steppes. The analysis of the 4 altitudinal transects together revealed that elevation is the main source of variation in species composition. Latitudinally, the 2 northernmost transects, similar between each other, differed from the 2 southernmost, mainly at intermediate elevation, where a high concentration of endemic rodents has been documented.

Agri-environment scheme enhances small mammal diversity and abundance at the farm-scale

The decline of farmland biodiversity over much of Europe has been largely attributed to agricultural intensification. Since the 1970s, governments have introduced agri-environment schemes (AES) aimed at mitigating this impact, but information on their success is limited. A five y, farm-scale experiment was conducted to test the efficacy of England's Environmental Stewardship AES in enhancing the species richness and abundance of small mammals (voles Cricetidae, mice Muridae, and shrews Soricidae) in an intensively-farmed arable landscape.Small mammal communities were sampled in spring and autumn on grassy field margins installed under the Entry Level Scheme (ELS) tier of Environmental Stewardship, where 1% of cropped land was converted to wildlife habitats. Results were compared with those from field margins on a second, experimental treatment (ELS Extra: ELSX) in which 5% of cropped land was taken out of production, and also field margins on a conventionally-farmed control treatment (‘cross compliance’: CC). Species richness and abundance of small mammals showed a significant increase on all treatments in spring and autumn. Many increases were greater on ELS and ELSX field margins compared to the CC controls, but there was little evidence that ELSX was more beneficial than ELS, and there were species-specific differences. Voles were not detected on any treatment in the initial sampling period but bank voles Myodes glareolus rapidly became abundant thereafter, particularly on ELS and ELSX field margins, and field voles Microtus agrestis also colonised. Wood mice Apodemus sylvaticus were present on all treatments in all sampling periods, but spring abundance declined as vole abundance increased.These results suggest that the Entry Level Scheme tier of the English agri-environment scheme is effective in enhancing small mammal communities on arable farmland, with potential benefits for higher trophic levels via their predators.

Patterns in community assemblage and species richness of small mammals across an altitudinal gradient in semi-arid Patagonia, Argentina

This is the first study that explored the altitudinal gradient in Argentine Patagonia. The purpose of this study was to document the effects produced by altitudinal gradients in the arid lands on the community composition, abundance, and species richness of small mammals. Four hypotheses of factors that influence the patterns of diversity proposed for mountain regions were assessed for Patagonian arid lands: reduction in the effective area, changes in biotic and abiotic parameters, isolation of montane communities and feedback between zonal communities. The study was carried out in the Somuncurá Protected Natural Area (500–1600 m a.s.l.), a basaltic plateau from northern Extrandean Patagonia. Mammals were sampled along altitudinal and vegetation gradients. With at least 20 small mammal species, Somuncurá is the place with the uppermost species richness in Patagonia. Small mammal abundance and species richness peaked at intermediate levels (750–1000 m a.s.l.), following a hump-shaped pattern. Temperature is the main factor to the structuring of small mammal communities in the arid lands and is the reason why height and latitude have a similar effect in the species composition. The same spatial pattern can be tracked throughout past climatic changes. Somuncurá should be considered at a higher priority level for conservation.

Relative abundance of small mammals in nest core areas and burned wintering areas of Mexican Spotted Owls in the Sacramento Mountains, New Mexico

Mexican Spotted Owls (Strix occidentalis lucida) are common in older forests within their range but also persist in many areas burned by wildfire and may selectively forage in these areas. One hypothesis explaining this pattern postulates that prey abundance increases in burned areas following wildfire. We observed movement to wintering areas within areas burned by wildfire by four radio-marked Mexican Spotted Owls in the Sacramento Mountains, New Mexico. These movements occurred during the winters of 2004–2005 and 2005–2006, with some owls migrating in both winters and others in only one. Wintering areas of these owls occurred within the perimeters of two wildfires that burned in May 2000 and April 2002, respectively. We estimated relative prey abundance and biomass during December 2006 within paired burned wintering areas and nest core areas used by these owls. Species richness and relative abundance of small mammals were greater in the burned wintering areas than in the associated nest core areas for all four owls, and estimated prey biomass ranged from 2–6 times greater in burned wintering areas relative to the paired nest core areas. Burned wintering areas used by these owls were similar in elevation to their nest core areas, and likely experienced similar weather conditions during winter. These results suggest that wintering owls moved to areas with greater food resources, rather than to areas with milder weather. They further suggest that relative prey abundance was greater in burned wintering areas than in the nest core areas >5 years post-fire, and that these burned wintering areas provided important habitat for Mexican Spotted Owls in our study area during an energetically stressful season.

Vector biodiversity did not associate with tick-borne pathogen prevalence in small mammal communities in northern and central California

Vector and host abundance affect infection transmission rates, prevalence, and persistence in communities. Biological diversity in hosts and vectors may provide “rescue” hosts which buffer against pathogen extinction and “dilution” hosts which reduce the force of infection in communities. Anaplasma phagocytophilum is a tick-transmitted zoonotic pathogen that circulates in small mammal and tick communities characterized by varying levels of biological diversity. We examined the prevalence of A. phagocytophilum in Ixodes spp. ticks in 11 communities in northern and central California. A total of 1020 ticks of 8 species was evaluated. Five percent of ticks (5 species) were PCR-positive, with the highest prevalence (6–7%) in I. pacificus and I. ochotonae. In most species, adults had a higher prevalence than nymphs or larvae. PCR prevalence varied between 0% and 40% across sites; the infection probability in ticks increased with infestation load and prevalence in small mammals, but not tick species richness, diversity, evenness, or small mammal species richness. No particular tick species was likely to “rescue” infection in the community; rather the risk of A. phagocytophilum infection is related to exposure to particular tick species and life stages, and overall tick abundance.

Elevation patterns in rodent diversity in the dry Andes: disentangling the role of environmental factors

Biodiversity patterns are the result of the interaction of numerous contemporary factors and historical opportunities for allopatric speciation. Several hypotheses regarding climatic features and topographic characteristics have been reported as determinants of species richness along elevation gradients. However, how these factors interact to shape small mammal species richness along the dry Andes ecosystem is not well understood. The objectives of this paper were to analyze patterns of species diversity along the central dry Andes, and to evaluate how climatic and topographic factors explain diversity patterns. Our results showed a positive and monotonic relationship between small mammal species richness and altitude, whereas abundance patterns showed a midelevation peak. Climate and topography were the most important predictor variables explaining small mammal species richness and abundance patterns in the Andes. This study underlines the role of the Andes in promoting and sustaining biodiversity, as well as the need to encourage conservation planning in mountain ecosystems.

Ecological correlates of small mammal assemblage structure at different spatial scales in the savannah biome of South Africa

We sampled the seasonal diversity of rodents and shrews in two neighboring game reserves in the savannah biome and assessed the influence of competition and abiotic processes on species composition patterns at habitat and reserve scales. We used null models and multivariate analyses to test whether the observed patterns differed significantly from those expected by chance. Species richness estimators indicated that rodent and shrew inventories were relatively complete. Rarefaction curves showed that small mammal species richness was higher at the Mkhuze Game Reserve than the Kube Yini Game Reserve, though it was highest in the Acacia woodlands. Rodent diversity was highest during winter. Rodent and shrew species composition was significantly correlated with grass height, tree density, and ground cover. Furthermore, rodent and shrew assemblages were nested at the reserve scale. Only nestedness at the broadest scale (both reserves, both seasons combined) was significantly correlated with landscape and microhabitat variables. Conversely, there was little evidence that competition influenced rodent and shrew species composition. Results showed that species composition patterns of small mammals in the savannah biome are related to abiotic processes operating at local and regional scales, suggesting that microhabitat characteristics and regional processes like immigration and extinction drive assemblage structure.

Geography, deer, and host biodiversity shape the pattern of Lyme disease emergence in the Thousand Islands Archipelago of Ontario, Canada.

In the Thousand Islands region of eastern Ontario, Canada, Lyme disease is emerging as a serious health risk. The factors that influence Lyme disease risk, as measured by the number of blacklegged tick (Ixodes scapularis) vectors infected with Borrelia burgdorferi, are complex and vary across eastern North America. Despite study sites in the Thousand Islands being in close geographic proximity, host communities differed and both the abundance of ticks and the prevalence of B. burgdorferi infection in them varied among sites. Using this archipelago in a natural experiment, we examined the relative importance of various biotic and abiotic factors, including air temperature, vegetation, and host communities on Lyme disease risk in this zone of recent invasion. Deer abundance and temperature at ground level were positively associated with tick abundance, whereas the number of ticks in the environment, the prevalence of B. burgdorferi infection, and the number of infected nymphs all decreased with increasing distance from the United States, the presumed source of this new endemic population of ticks. Higher species richness was associated with a lower number of infected nymphs. However, the relative abundance of Peromyscus leucopus was an important factor in modulating the effects of species richness such that high biodiversity did not always reduce the number of nymphs or the prevalence of B. burgdorferi infection. Our study is one of the first to consider the interaction between the relative abundance of small mammal hosts and species richness in the analysis of the effects of biodiversity on disease risk, providing validation for theoretical models showing both dilution and amplification effects. Insights into the B. burgdorferi transmission cycle in this zone of recent invasion will also help in devising management strategies as this important vector-borne disease expands its range in North America.

Assessment of small mammal diversity in coffee agroforestry in the Western Ghats, India

Coffee agroforestry is a conservation strategy that has shown promise to support the diversity of bird, bat, and insect communities, but few studies have focused on non-volant mammals in coffee farms. We assessed mammal diversity within coffee agroforestry systems in Kodagu, India and investigated the impacts of the non-native shade tree species, Grevillea robusta, on mammal diversity. Twenty farms, with varying amounts of G. robusta planted within the coffee farm, were sampled throughout three rainfall zones during the 4-month study period. We captured six species of small mammals, with indirect methods yielding an additional five species, totaling 11 mammal species. Contrary to current ecological thought, we found that increased amounts of G. robusta did not have a negative impact on either abundance or richness of mammals. Small mammal abundances were higher at farms with greater amounts of herbaceous ground cover and larger, mature shade trees, while small mammal species richness was found to increase with an increase in tree species richness as well as greater amounts of herbaceous ground cover. Additionally, small mammal abundance was higher at coffee farms closer to forested areas. Based on these findings, we suggest the maintenance or cultivation of shade tree richness, mature shade trees, and herbaceous ground cover within coffee farms and preservation of forested areas within the landscape to enhance coffee agroforestry habitat for non-volant mammals. We hope that these habitat requirements will be incorporated into conservation strategies for the promotion of biodiversity within coffee agroforestry systems.

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.

Does woodland condition influence the diversity and abundance of small mammal communities?

Loss of mammal species in Australia in the last 200 years has been attributed to many factors including habitat removal and altered fire regimes. Decline in tree condition could contribute further to the ongoing decline of mammals. Eucalyptus wandoo trees are currently undergoing a decline in condition that can result in a loss of canopy and other changes to the habitat. This paper examines the relationships between E. wandoo tree condition, habitat characteristics and small mammal species richness and abundance. Live-capture trapping was conducted at 24 E. wandoo sites at Dryandra State Forest and Wandoo Conservation Park, Western Australia. Condition and microhabitat variables of E. wandoo were recorded for each site. Generalised additive mixed models revealed a range of habitat and tree condition characteristics that influenced small mammal abundance and species richness, including site litter cover, crown dieback, understorey vegetation cover and tree density. The availability of coarse woody debris played a large role in explaining the abundance of Cercartetus concinnus and Antechinus flavipes, along with other microhabitat and tree condition variables, such as tree leaf litter and crown dieback. Epicormic growth, crown density and the distance to the drift fence from E. wandoo trees were the common variables in the best model for the abundance of Sminthopsis griseoventer. The decline in condition of E. wandoo and the subsequent modifications to the microhabitat are correlated with changes in the small mammal community. A better understanding of how the decline of E. wandoo impacts small mammal communities could improve management practices in E. wandoo woodlands.

Desert small mammal responses to wildfire and predation in the aftermath of a La Nińa driven resource pulse

AbstractIn arid Australia, flooding rains associated with the La Nińa phase of El Niño/Southern Oscillation (ENSO) prompt dramatic pulses of primary productivity, which in turn result in irruptions of rodents and their predators. When it is dry, the dense vegetation produced by extreme rainfall events can fuel extensive wildfires. In this study we investigated the effects of a wildfire that followed exceptional rainfalls associated with the La Niña event of 2010–2011 on small mammal assemblages in a stony (gibber) desert ecosystem in central Australia. When the study commenced in July 2011, there was dense grass cover and rodents, particularly, Rattus villosissimus occurred at high abundance. Mammalian predator activity was high throughout the study period and predators primarily consumed rodents. A wildfire in October 2011, reduced grass cover but there was no effect of fire on the abundance or species richness of small mammals, immediately after the wildfire or 11 months after the wildfire. Following the fire event, grass cover increased on both burnt and unburnt grids, but did not reach the levels recorded prior to the wildfire. Small mammal abundance and species richness declined steadily during the study irrespective of the occurrence of wildfire. At 6 and 11 months after the wildfire there was no difference in grass cover on burnt and unburnt grids and Rattus villosissimus were absent. Our results show that the removal of vegetation by wildfire was not a major driver of small mammal assemblage structure in this stony desert ecosystem. Our results are consistent with the predictions of ecosystem organization models that describe switching trophic control along gradients of resource productivity and support the notion that the decline of small mammals was driven by the onset of top‐down control by abundant predators coupled with diminished availability of food resources.

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

Termites, Large Herbivores, and Herbaceous Plant Dominance Structure Small Mammal Communities in Savannahs

Large herbivores and termites are important functional groups in African savannahs. Both groups affect small mammals, which are also important determinants for savannah structure and function. Because vegetation on Macrotermes mounds are preferentially grazed by large herbivores, and mounds represent resource-rich distinct habitat patches for small mammals in relatively resource-poor savannahs, termite mounds are ideal sites for studies of how grazing by large mammals and productivity affect communities of small mammals. We conducted an experiment in Lake Mburo National Park, Uganda, with four treatments: large vegetated Macrotermes mounds (with and without large herbivores) and adjacent savannah areas (with and without large herbivores). We replicated the treatment blocks nine times and trapped small mammals regularly over a period of almost 2 years. Small mammal species assemblages differed considerably between mounds and savannah areas. Grazing had a substantial effect on small mammal species assemblages in the resource-poor savannah, but not in the relatively resource-rich termitaria. Small mammal species abundance, biomass, and richness were higher on termite mounds than adjacent savannah areas. Excluding large herbivores caused a major increase in species abundance, biomass, and richness both on savannah and termitaria. Herbaceous plant species evenness was an important determinant of the small mammal community. Small mammal biomass increased with high plant dominance, indicating that a few dominant plant species are important for biomass production of small mammals. Small mammal diversity was not related to any of the treatments, but increased with plant species evenness as well as richness. Fencing increased species dominance in the small mammal community on both savannah and termitaria, probably because competitive patterns shift from inter-guild (that is, between large and small mammals) to intra-guild (that is, between small mammals) when large mammals are excluded. The study highlights the complex interactions among large herbivores, termites, herbaceous plants, and small mammals in African savannahs. When studying the structure and function of small mammal communities it is therefore important to consider several coexisting functional groups.

Elk herbivory alters small mammal assemblages in high‐elevation drainages

Heavy herbivory by ungulates can substantially alter habitat, but the indirect consequences of habitat modification for animal assemblages that rely on that habitat are not well studied. This is a particularly important topic given that climate change can alter plant-herbivore interactions. We explored short-term responses of small mammal communities to recent exclusion of Rocky Mountain elk (Cervus elaphus) in high-elevation riparian drainages in northern Arizona, where elk impacts on vegetation have increased over the past quarter century associated with climate change. We used 10-ha elk exclosures paired with unfenced control drainages to examine how browsing influenced the habitat use, relative abundance, richness and diversity of a small mammal assemblage. We found that the small mammal assemblage changed significantly after 5years of elk exclusion. Relative abundance of voles (Microtus mexicanus) increased in exclosure drainages, likely due to an increase in habitat quality. The relative abundances of woodrats (Neotoma neomexicana) and two species of mice (Peromyscus maniculatus and P.boylii) decreased in the controls, while remaining stable in exclosures. The decline of mice in control drainages was likely due to the decline in shrub cover that they use. Thus, elk exclusion may have maintained or improved habitat for mice inside the exclosures while habitat quality and mouse abundance both declined outside the fences. Finally, small mammal species richness increased in the exclosures relative to the controls while species diversity showed no significant trends. Together, our results show that relaxation of heavy herbivore pressure by a widespread native ungulate can lead to rapid changes in small mammal assemblages. Moreover, exclusion of large herbivores can yield rapid responses by vegetation that may enhance or maintain habitat quality for small mammal populations.

Life on high: the diversity of small mammals at high altitude in South Africa

The Great Escarpment is the major mountain system in South Africa, yet very few biological surveys have been conducted outside of the well-known Drakensberg section. This is surprising given the important role that mountains play in local and global biodiversity patterns. In this study, small mammal diversity and community composition were estimated at three high altitude (>1,700 m) sites within the Sneeuberg Mountain Complex (SMC) of the Great Escarpment, South Africa from June 2009 to May 2010. The influences of selected environmental variables on diversity were also tested. Of 423 live-captures, a total of 292 unique individuals of 12 small mammal species (one shrew, one elephant shrew and 10 rodents) were identified during 5,280 trap nights. No single environmental variable could account for the variation observed in diversity measurements but vegetation height appeared to be the most important factor to influence the number of individuals captured. It is hypothesised that the high species richness and diversity of small mammals observed in the SMC compared to other parts of the Great Escarpment is due to the SMC being located in a transition zone of the Grassland and Nama-Karoo biomes. Our results suggest that the SMC could be important in conserving small mammal species from western and eastern assemblages across South Africa.