Small Mammal Composition Research Articles

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.

New mammal species for Latvia, the root vole (Microtus oeconomus)

In the summer of 1989, a single adult male root vole (Microtus oeconomus) was trapped in the meadow at Kovaliski, Latvia. It was registered in the site, characterised by low small mammal diversity (nine species, Shannon’s H = 0.97). Among three sampled habitats in the Kovaliski site, meadow had most diverse small mammal composition, while forest and swamp were characterised by three species each in the period of 1984–1990. This is the first record of M. oeconomus for Latvia, thereby also expanding the known distribution range. This finding is very much in line with the north and eastward spread of the species in Lithuania, an expansion that started in the Nemunas Delta and, at least partly, tied to land abandonment in the years since the 1990s creating suitable habitat for M. oeconomus. Its distribution in Baltic countries is still however limited to Lithuania and, possibly, closely adjacent areas in Latvia. Old records of M. oeconomus from Estonia were not confirmed in the last decades.

Landscape-scale features affecting small mammal assemblages on the northern Great Plains of North America

Abstract Little is known about the macrohabitat associations of rodents and shrews in prairie landscapes because of the logistic constraints of conventional trapping. We used the remains of 60,972 small mammals in owl pellets to assess factors affecting small mammal composition across 4.3 million hectares of the northern Great Plains of North America. Cropland with clay soils was dominated by deer mice (Peromyscus maniculatus), whereas areas with higher proportions of native grassland and moderately sandy soils supported communities with more sagebrush voles (Lemmiscus curtatus). Areas with clay soils and higher annual precipitation were associated with higher proportions of house mice (Mus musculus), meadow voles (Microtus pennsylvanicus), and shrews (Blarina brevicauda and Sorex species), whereas drier areas with sandier soils and lower annual precipitation were dominated by olive-backed pocket mice (Perognathus fasciatus) and northern grasshopper mice (Onychomys leucogaster). Contrary to extrapolations...

Seasonal variation of small mammals in the diet of the barn owl (Tyto alba) in the Drinos River valley, southern Albania

The small mammal composition in the diet of barn owls from the Drinos River valley, southern Albania, was studied over the period of 1 year (September 2010-September 2011). A total of 662 pellets was collected and analyzed, and 1951 prey items were identified. Fourteen different small mammal species were identified (5 insectivores and 9 rodents), among which Microtus thomasi (frequency, F = 32.9%; biomass, B = 45.5%), Crocidura suaveolens (F = 23.5%; B = 9.4%), and Mus macedonicus (F = 17.8%; B = 16.3%) were the most abundant. In winter, Rattus rattus increased significantly in the consumed prey biomass (18.1%), while in spring Apodemus sylvaticus (9.4%) ranked third most common among the prey species. Neomys anomalus was more frequent in the diet in autumn and winter than in spring and summer. Suncus etruscus had low percentages in the barn owl diet, but was preyed upon during all seasons, confirming the presence of the species in the Drinos valley. Significant seasonal variations in small mammals in the diet of the barn owl were detected. Environmental index (i/r) values indicate that the Drinos valley is mainly an agrocenosis of nonintensive land-use practices.

Long term variations in small mammal composition of a snake diet do not mirror climate change trends

The study of the dietary changes which have intervened over the years in generalist and opportunist predators may provide useful information on the temporal modifications of their prey communities, especially under a climate change scenario. In this study, we analysed the quantitative changes in the small mammal portion of the diet of a generalist and opportunist predator, the asp viper (Vipera aspis) at a forest zone in central Italy, for the period 1987–2010. In addition, small mammals were trapped in five of these years. Apodemus spp., Mus musculus, and Myodes glareolus were the main prey for vipers. Among the various taxa eaten by vipers, only two showed significantly consistent trends over the years, with M. glareolus increasing and Sorex spp. declining in the viper diet. There were no significant relationships between the number of years passed after the first year of sampling and the diversity and dominance indexes of prey composition. We also found a significantly positive relationship between small mammal abundance in the field and their relative frequency of occurrence in the viper's diet, thus demonstrating that vipers really sampled the small mammal species in relation to their local availability. Despite being temperate-zone forest-associated species, hence likely adversed by global warming, Sorex spp. and M. glareolus showed opposite trends over the years, thus suggesting that such trends may reflect more local scale perturbations (local forest overgrowth and diminution of logging).

Habitat patch and matrix effects on small-mammal persistence in Amazonian forest fragments

Tropical forest mammal assemblages are widely affected by the twin effects of habitat loss and habitat fragmentation. We evaluated the effects of forest patch metrics, habitat structure, age of patch isolation, and landscape metrics on the species richness, abundance and composition of small mammals at 23 forest fragments (ranging in size from 43 to 7,035 ha) in a highly deforested 3,609-km2 landscape of southwestern Brazilian Amazonia. Using pitfall traps and both terrestrial and arboreal traplines of Sherman, Tomahawk and snap traps, we captured a total of 844 individuals over 34,900 trap-nights representing 26 species and 20 genera of small-mammals, including 13 rodent and 13 marsupial species. We also consider the effects of distance from forest edges on species occupancy and abundance. Overall small mammal abundance, species richness and species composition were primarily affected by the quality of the open-habitat matrix of cattle pastures, rather than by patch metrics such as fragment size. Ultimately, small mammal community structure was determined by a combination of both landscape- and patch-scale variables. Knowledge of the anthropogenic factors that govern small mammal community structure is of critical importance for managing the persistence of forest vertebrates in increasingly fragmented neotropical forest landscapes.

Effects of altitude and vegetation on small-mammal distribution in the Urucum Mountains, western Brazil

Abstract:We conducted a study on small-mammal composition, abundance and diversity across altitudinal and vegetational gradients in the Urucum Mountains (from 150 to 1000 m asl) in western Brazil, a complex biogeographic region. Small mammals were collected in 31 sampling units distributed along altitudinal and vegetational gradients (forest and grassland), totalling 18 112 trap-nights for pitfall and 3500 trap-nights for live-trap. Community variation among sampling units was assessed by randomization tests, setting altitude, vegetation, locality and time as factors, and using presence/absence data. Correlation and logistic regression analyses were run for species and diversity along gradients of altitude and vegetation, according to abundance and presence/absence data. Nineteen species (seven marsupial and 12 rodent) and 355 individuals were recorded. The species composition of small mammals differed according to altitude, vegetation type, locality and time. Species diversity varied significantly according to altitude. Species were influenced solely by altitude or vegetation, or by both vegetation and altitude concomitantly. The small-mammal community was divided in two groups according to biogeographic affinities. The grassland group is capable of invading forest habitats. The results are discussed in light of current hypotheses that attempt to explain community variation along altitudinal gradients around the world.

Non-volant small mammals of the Western Ghats of Coorg District, southern India

A study to understand diversity and changes in non-volant small mammal composition in the Western Ghats of Coorg District, Karnataka was conducted from April 2004 to April 2008. A total of 11060 trap nights of sampling in various habitats such as forest fragments, coffee and cardamom plantations, open areas including grasslands, agricultural fields including paddy and ginger cultivations, bamboo and in and around human habitations across the two vegetation zones of the district. Totally, 14 species of non-volant small mammals were trapped as 412 unique individuals contributing to an overall trap success of 3.8%. Rattus wroughtoni was the most commonly caught taxon followed by Suncus murinus and S. niger although S. murinus was trapped in 10 habitats followed by Mus musculus in 9 of 11 habitats. The abundance of small mammals was the highest in bamboo (12.1%) and in forest fragments (7.2%); the plantations supported very low abundances (< 3.1%). Endemic mammals such as Rattus satarae, Vandeleuria nilagirica, Platacanthomys lasiurus, Funambulus tristriatus and Suncus niger were recorded in Coorg although P. lasiurus and V. nilagirica were trapped in only one habitat each. Changes in land use and rapid decline in quality of habitat is pushing the endemics into local extinctions while non-endemic commensals are displacing restricted endemics in disturbed habitats. This study underlines the need for more in-depth rapid assessments in the Western Ghats for the poorly understood small mammals and the initiation of conservation programmes for endemics.

Evaluation of Total Body Electrical Conductivity to Estimate Body Composition of a Small Mammal

ABSTRACT The ability to measure body composition is critical for studying the physiological ecology of animals. This is particularly true for small mammals that have a high metabolic rate. We evaluated a nondestructive method of body composition analysis that would allow accurate assessment of body fat, body water, and lean mass. We used total body electrical conductivity (TOBEC) to estimate body composition in the little brown myotis (Myotis lucifugus). In a sample of 46 individuals, TOBEC was both accurate and precise in estimating total body water and lean mass but was less effective at estimating total body fat. Mass‐independent or whole‐body compartments (i.e., total body water, total body fat, lean dry mass, and lean body mass) were more accurately estimated than mass‐dependent or mass‐specific body composition compartments (i.e., water content, fat index, and % lean dry mass). The TOBEC measurements we made using an SA‐3000 analyzer were influenced by extremes in body temperature, as well as by aluminum and incoloy wing bands. Our study also presents a new method of restraint especially suited for small mammals and birds that increases precision of TOBEC measurements. This study shows that TOBEC is a potentially valuable tool for studying changes in body composition of small mammals and may provide insight into the physiological impacts of various life history stages such as postnatal growth, reproduction, and hibernation.

Towards an ecologically-sustainable forestry in the Atlantic Forest

Since pristine Atlantic Forest remnants are vanishing, and biological reserves are in short, conservation of biodiversity will largely depend on proper management of the anthropogenic matrix. Here, we test (1) the effectiveness of ecologically-managed tree monocultures in maintaining Araucaria Forest biodiversity, (2) how this effectiveness change among taxa, and (3) we discuss management principles that can be used by the forestry industry in order to contribute positively to biodiversity conservation. The study was conducted in the São Francisco de Paula National Forest, southern Brazil, an environmental mosaic composed mostly of patches of Araucaria Forest and ecologically-managed monocultures of Araucaria, Pinus and Eucalyptus. Using standardized sampling methods in these four main habitats, we have recorded the richness and species composition of small mammals, birds, leaf-litter frogs, butterflies, galling insects, spiders, opiliones, flatworms, woody plants, epiphytic angiosperms, epiphytic ferns, lichens, and fruit-body producing fungi. Overall, we recorded 506 species in Araucaria Forest, 181 (36%) of which were exclusive of this habitat while 325 (64%) could be found in at least one monoculture. Distribution patterns of species richness and number of records across taxonomic groups showed that a large biodiversity can be found inside ecologically-managed plantations of Araucaria, Pinus, and Eucalyptus. For all studied taxa, except for epiphytic angiosperms and fruit-body producing fungi, more than half of the Araucaria Forest species could be found living on monocultures. We discuss how the actual management practices of the forest industry can be improved to contribute positively to the conservation of the Atlantic Forest biodiversity.

Land use vs. fragment size and isolation as determinants of small mammal composition and richness in Atlantic Forest remnants

The remaining Atlantic Forest fragments are structurally isolated by a matrix of pastures, plantations, or urban areas, and most remnants are small (<100ha). Island biogeography theory has been used to predict the effects of such fragmentation in the remaining fragments, but human activities and land use around fragments may be equally important. A related question is which aspects of land use have a strong effect on biodiversity. We compare the relative importance of fragment size and isolation vs. land use around fragments as determinants of composition and richness of small mammals in Atlantic Forest fragments. We also compare two aspects of land use around fragments, economic activity (peri-urban, agriculture, cattle), and property ownership (peri-urban, low income rural producers, affluent rural producers). Small mammals were surveyed in 21 fragments varying from 12 to 250ha, and in two sites of continuous forest in the Macacu River watershed, State of Rio de Janeiro, Brazil, from 1999 to 2007. The effects of land use, fragment size and isolation were formulated as eleven candidate models, compared by Akaike Information Criteria. In the models selected, species composition was associated more strongly with fragment size, followed by isolation, with a smaller effect of property ownership. Species richness was determined mostly by fragment isolation, but also by a negative effect of agriculture when it was the dominant economic activity. Regardless of the critics to island biogeography theory, fragment isolation and size were by far the most important determinants of species composition. Economic activity and property ownership allowed the detection of subtle but important effects of land use on species composition and richness.

Effects of rain forest logging on species richness and assemblage composition of small mammals in Southeast Asia

AbstractAim The effects of logging and habitat degradation on the richness and abundance of small mammals in Asian rain forests are largely unknown. This work compares the species richness, dominance and evenness of small non‐volant mammals between logged and unlogged forests, and assesses whether assemblage variability (β‐diversity) is similar between forest types.Location Southeast Asia, northern Borneo (Sabah, Malaysia), Sunda‐shelf.Methods We surveyed species‐rich assemblages of small non‐volant mammals in three unlogged and three logged forests for 2 years. At each forest site, we sampled a permanently marked transect and two additional sites in three trapping sessions. All analyses were performed at both levels to include the effects of local abundances and point estimates, separately from the relative abundances of species on a more regional scale.Results We trapped a total of 1218 individuals of 28 species. Eleven common species accounted for 95% of all captures. Species richness and diversity were significantly higher in unlogged forest (27 species) than in logged forest (17 species). This was mainly attributable to the smaller number of rarely recorded species in logged forest (five compared with 16 in unlogged forest, with a total of fewer than 10 captures). However, all common species were present in both logged and unlogged forests, and our analyses revealed similar patterns of dominance, evenness and fluctuations in abundance. Hence overall assemblage composition in multivariate space did not differ greatly between forest types. Assemblages of Muridae and Tupaiidae showed similar population fluctuations in space and time, indicating that the ecology of these taxa may be partially driven by the same environmental factors.Main conclusions Although species were distributed patchily within sites, analyses at local and regional scales revealed similar patterns in diversity and assemblage variability, suggesting that effects of forest modification did not differ extensively locally and regionally, but had a profound effect on rare species. Our results emphasize the importance and conservation value of logged forest stands that are able to hold a large proportion of the small mammals also found in unlogged forests. Rare and more specialized species are more vulnerable to forest degradation than commonly caught species, resulting in the complete loss, or a decrease in numbers, of certain groups, such as arboreal small mammals and Viverridae.

Small Mammal Communities in the Fragmented Landscape in Lithuania

Species composition and abundance of small mammals, as well as changes in small mammal communities after the abandonment of agriculture fields, were studied in forest fragments and the surrounding field matrix. The most common species in the forest fragments was the bank vole (Clethrionomys glareolus), in the fields – the common vole (Microtus arvalis). C. glareolus and the yellow-necked mouse (Apodemus flavicollis) had the highest frequency of occurrence, both recorded in 82% of the investigated forest fragments. Other species were less common. The relative abundance of small mammals did not differ in the surrounding field matrix and the forest fragments irrespective of their size. In small forest fragments, species composition of small mammals was not stable. After the abandonment of the surrounding field, the diversity of a small mammal community in the forest fragments decreased. Our study suggests that C. glareolus was the only small mammal species in the forest fragments that positively responded to matrix changes from the start of the forest re-growth in the former agricultural field during the first years of succession.

Small mammals of Maulino forest remnants, a vanishing ecosystem of south-central Chile

The Maulino forest, located at the coastal range of south central Chile, has been severely disrupted by intense human activities. Currently, landscape is dominated by large extensions of plantations of Monterrey pine, where remnants of native forest are immersed. Here, we assess consequences of Maulino forest fragmentation and habitat replacement upon small mammal fauna. We describe habitat characteristics, small mammal's composition and abundance in native forests (fragmented and continuous), but also in Pinus plantation. Population and body condition were compared among habitats, along with movement among native and Pinus forests. Higher species richness was found in continuous forest comprising Abrothrix longipilis, A. olivaceus, Oligoryzomys longicaudatus, Irenomys tarsalis, Geoxus valdivianus, Rattus rattus, Octodon bridgesi, Thylamys elegans, and Dromiciops gliroides. Higher abundance was observed in fragmented forest and Pinus plantations, where A. longipilis, A. olivaceus, O. longicaudatus, and T. elegans accounted for 80% of total captures. Population structure and body size were not affected negatively by fragmentation and habitat replacement, although habitat characteristics differed among surveyed habitats. Fragmentation of Maulino forests seems to have a significant impact on overall small mammal's richness, threatening the persistence of rare taxa of small mammals. Conservation and management practices are discussed to favor protection of this highly endangered habitat.

Relation between small-mammal species composition and anthropic variables in the Brazilian Atlantic Forest

Anthropic activities are frequently related in many ways to forest fragmentation and alteration of natural communities. In this study, we correlate the presence of hunting, tourism activity, agriculture/pasturing, and the distance of the study sites to the nearest human residences with the species composition of small Atlantic forest mammals. To do this, we utilize a multiple regression analysis of similarity matrices. The presence of both agriculture/pasturing and human residences near the study sites proved to be determinant factors in species composition of small mammals of the studied areas. Working with socioeconomic variables related directly with the study site could be a reliable and a direct way to predict the influence of human presence and entailed activity on small mammal communities.

Effects of clearcutting with corridor retention on abundance, richness, and diversity of small mammals in the Coastal Plain of South Carolina, USA

We studied six pine plantations in coastal South Carolina to determine the influence of clearcutting with corridor retention on small mammal abundance, richness, and diversity. Small mammals were live-trapped in recently clearcut stands that retained pine corridors 100 m in width and in adjacent pine plantations, 20–23-years-old. We compared small mammal communities between harvested stands with corridors and non-harvested pine stands. We captured 1158 small mammals, representing 844 unique individuals and seven different species in 94,080 trap nights. Rodent abundance, richness, and diversity indices were greater in harvested stands with corridors than in non-harvested pine stands. The early successional habitat created by clearcutting was used by many small mammal species, including cotton rats ( Sigmodon hispidus) and marsh rice rats ( Oryzomys palustris). Species composition of small mammals within the corridor habitats was similar to that in the non-harvested pine stands. The inclusion of corridors in pine plantation management enhances habitat diversity and ecosystem maintenance and contributes to local diversity of the small mammal community.

Sexual dimorphism in body composition of small mammals

Differences in reproductive roles between the sexes may lead to sexual dimorphism in body composition. Body size and composition of three species of small mammals (bushy-tailed wood rats (Neotoma cinerea Ord), deer mice (Peromyscus maniculatus Wagner), and red-backed voles (Clethrionomys gapperi Vigors)) were analyzed to test the predictions that (i) males will have more muscle mass than females and (ii) females will have more fat than males. Results supported the first prediction but not the second. For all three species, males had more lean dry mass relative to body size than females, but females did not have relatively more fat than males. Muscle mass of males may aid in mate-searching and mate-guarding activities, but fat content may not differ between the sexes because female small mammals depend on increased ingestion rates, rather than fat stores, to support reproduction.

Land fauna composition of small mammals of a fragment of Atlantic Forest in the State of Sao Paulo, Brazil

The Atlantic Forest small mammal land fauna, except bats, and the abiotic factors that might have an influence on its composition, were studied in the Itapevi County, State of Sao Paulo, a forested region, partly altered by antropic action, from January, 1995 to June, 1996. The trapping effort consisted of 2,888 trap-nights, resulting in a 4.6% trapping success and consisted of monthly trappings, for five consecutive days. During this period, 134 specimens were captured, of which 46.3% were Didelphimorphia and 53.7% were Rodentia. Eleven species were registered: two Didelphimorphia: Didelphis marsupialis (Linnaeus, 1758) and Marmosops incanus (Lund, 1841), and nine Rodentia: Akodon cursor (Winge, 1887), Bolomys lasiurus (Lund, 1841), Oxymycterus hispidus Pictet, 1843, Oxymycterus nasutus (Waterhouse, 1837), Oligoryzomys nigripes (Olfers, 1818), Oryzomys angouya (Fischer, 1814), Raltus norvegicus (Berkenhout, 1769), Euryzygomatomys spinosus (G. Fischer, 1814) and Cavia aperea Erxleben, 1777. The relative density indices were correlated with meteorological data by Spearman and Pearson coefficients. For marsupials these correlations were not significant. For rodents, the correlations were significant and directly related to lower temperature and rainfall indices (p<0.05). During the dry season the occurrence of small mammals was 50% greater than during the wet season, probably due to foraging strategies in the studied fragment of Atlantic Forest.

Diversity and structure of terrestrial small mammal communities in different vegetation types on the Accra Plains of Ghana

AbstractSmall mammal communities (shrews and rodents) were studied using mark‐and‐recapture techniques from November 1991 to June 1992 at six sites on the Accra Plains of Ghana. The sites were two traditionally protected ‘sacred groves’, two plots in the legally protected Shai Hills Resource Reserve, and two fire‐protected sites: secondary forest and a Gmelina tree plantation. A total of 241 individuals representing four species of shrews and nine species of rodents was caught. Abundance, diversity, and composition of small mammals varied greatly between sites. Praomys tullbergi was the most abundant species in the sacred groves, whereas Mastomys erythroleucus dominated in the fire‐protected site and in the plantation. The more open grassland areas in the Shai Hills were dominated by Lemniscomys striatus and Uranomys ruddi. Shrews were caught only in forests having dense leaf litter. Legally protected reserve sites had the highest diversity of small mammals but population densities were low. In contrast, the sacred groves had lower diversity levels but much higher population densities, resulting in 1.9 to 14.6 times the biomass of any of the other sites. The rodents Mus minutoides and Hylomyscus alleni and the shrews Crocidura buettikoferi and C. lamottei were found only in the sacred groves. Sacred groves play an important socio‐cultural role. Their local ecological and economic importance as reservoirs for rare and useful plants is well known. This study shows that they are also important refuges for certain small mammal species and support characteristic mammal communities. An attempt to measure the impact of the invading exotic tree Azadirachta indica (neem tree) on small mammals was inconclusive, although trapping success was low in areas with dense stands of neem.

Small Mammals of the Ituri Forest, Zaire: Diversity and Abundance in Ecologically Distinct Habitats

Small-mammal diversity and abundance were examined in two primary forests (mixed and mbau forests) and two disturbed habitats (secondary forest and village fields) in the Ituri Forest of Zaire (Democratic Republic of Congo). Small-mammal species observed were Deomys ferrugineus, Hybomys univittatus, Hylomyscus Stella, Lophuromys flavopunctatus, Malacomys longipes, Mus minutoides, Oenomys hypoxanthus, and Praomys jacksoni. Secondary forest was the most species-rich of the four habitats examined. Mixed forest exhibited significantly higher species diversity of small mammals than mbau forest. The difference in the composition of small mammals reflected the difference in the composition of tree species between species-rich (mixed and secondary) forests and the species-poor (mbau) forest. Small mammals in village fields were not true forest species but typically were found in a wide variety of habitats. This study provides a benchmark of the ecology of small mammals in the Ituri Forest of Zaire prior to increased human disturbance.