Total Abundance Of Small Mammals Research Articles

К совершенствованию неинвазивного метода оценки обилия мышевидных грызунов и землероек в городской среде

Previously we proposed a new reconnaissance method for estimating the total abundance of small mammals in urban areas. The method includes placing plastic bottles with bait inside equal distances apart. In this research we examined two ways to improve the method: using bottles of smaller volume (0,25 liters instead of 0,5 liters) to increase the ergonomics and using opaque bottles to make them more attractive for animals. Bigger and smaller bottles with neck diameter of 38 mm were fastened in pairs which were set in a transect with a five-meter spacing. The same was done with pairs of opaque and transparent bottles. A bait (rye bread with unrefined sunflower oil) was put into all the bottles. During the following days we recorded animals’ visits into the bottles. It was found out that there are no significant differences in how often animals attend bottles of 0,25 liters and 0,5 liters, the same results were received for both transparent and opaque bottles. Thus, the simple method for estimating abundance of small mammals may be optimized by using smaller bottles, the colour of which is not important.

СООБЩЕСТВА МЕЛКИХ МЛЕКОПИТАЮЩИХ СЕВЕРНОЙ ЛЕСОСТЕПИ ТОБОЛО-ИШИМСКОГО МЕЖДУРЕЧЬЯ

The paper summarises the material on the communities of small mammals in the northern forest-steppe of the Tobol-Ishim interfluve (the South Trans-Ural region). A brief history of the study of this group of animals is reviewed. The use of two accounting methods (cones with guide systems and trap lines) made it possible to identify the species composition most fully. 18 species of insectivores and rodents have been registered in the studied territory. At the same time, the species composition, the group of background and dominant species, and the indicators of the total abundance of small mammals in the studied territory were largely determined by the specifics of the animal accounting method. The core of small mammals of the northern forest-steppe of the Tobolo-Ishim interfluve consisted of species tending to moistened habitats – common and pigmy shrew. In general, regardless of the method of accounting animals, they were characterized by low abundance in the study period.

Динамика населения мелких млекопитающих пирогенных сообществ в степном бору

In 2008–2021 we studied small mammals annually using zoological ditches in the Tsasucheysky steppe pine forest (Zabaikalsky Region, Russia). Before the 2012 high-severity fire we captured small mammals in a typical pine forest, either old-growth or old-burnt sites, and after the 2012 fire—in sites of fresh primary and repeated burns as well as in survived areas. The undisturbed steppe pine forest was characterised by small numbers of mammals, dominated by Myodes rutilus. In the first-burnt sites mainly Cricetulus pseudogriseus individuals were captured during the first decade after the fire. This species also rapidly invaded the re-burnt sites; however, in the third or fourth year the small mammal community became polydominant. In the old post-fire area (more than 10 years after the fire) small mammals were most abundant and the community was more diverse. In the post-fire sites С. pseudogriseus, Lasiopodomys raddei, Sorex tundrensis and S. minutissimus were the most numerous; Alexandromys mongolicus was also common in the old burnt sites. The total number of small mammals decreased significantly only in the first year after the fire. The total abundance of small mammals in the sites of old and repeated burns was significantly higher than in the undisturbed pine forests and first burned areas. In parallel, the total numbers of small mammals in the pyrogenic and relevant preceding communities were not statistically different. The number of M. rutilus decreased and the number of C. pseudogriseus increased in the burns compared to the pine forest. Despite the changes in the composition and structure of the community, the fire led to no significant changes in the overall abundance of small mammals in the Tsasucheysky Pine Forest during the first following decade. Subsequently, when the burns became overgrown, the small mammal community became richer in both number of species and their abundance. This indicates the resilience of small mammal populations to fires in the forest-steppe and, thus, the stability of the food base for small mammal predator populations.

Seasonal variation of non-volant small mammals in Gibe Sheleko national park, Southwestern Ethiopia

The species composition and abundance of small mammals can vary within space and time. The main objective of this study was to assess seasonal variation of non-volant small mammals from randomly selected Acacia woodland, bushland, farmland, grassland, riverine forest and wooded grassland habitats in Gibe Sheleko National Park, southwestern Ethiopia. Data were collected using 49 Sharman live traps in 70 x 70 m sized square girds from December, 2018 to August, 2020. Capture mark recapture technique was applied to estimate population size of the existing small mammals and the data were analyzed using a chi-square test. A total of 1160 individual small mammals belonging to 10 species and 2 families were recorded. Three non-captured species: Hystrix cristata, Xerus rutilus and Tachyoryctes splendens were also identified. There was a significant (χ2= 31.12, df = 1, P < 0.05) difference in the total abundance of small mammals between seasons. Of the total individuals captured, 675(58.19%) were trapped during the wet season while 485(41.81%) individuals were during the dry season. Significant seasonal variation was also observed in the total abundance of both sexes, i e. males (χ2= 11.99, df = 1, P < 0.05) and females (χ2= 20.24, df = 1, P < 0.05). Among age groups, significant statistical seasonal variation was shown in adults (χ2=15.14, df = 1, P < 0.05) and young (χ2=44.61, df = 1, P < 0.05) but not significant in sub-adults (χ2=0.75, df = 1, P >0.05). The identified small mammals exhibited seasonal changes in their abundance associated with changes in climatic and environmental conditions. However, a long-term and annual based study is required to see the overall dynamics of existing small mammals.

The effect of the character of urban development on the small mammal communities in a northern city

Communities of small mammals on the territory of Yakutsk and in its vicinity have been studied. Residential areas, undeveloped sites, suburban zone, and agricultural lands are covered. A total of 2,736 cone-days and 525 trap-days are accumulated and 388 specimens of small mammals from 13 species belonging to Rodentia and Eulipotyphla orders are collected. The abundance of small mammals in different types of environment have varied from 2.2 to 22.9 individuals per 100 cone-days. The highest values of species diversity are found in the suburban zone in the areas of surviving natural biotopes. The zone of the city’s residential areas is characterized by the lowest abundance and species diversity of small mammals, primarily Eulipotyphla, and also by the presence of eusynanthropicMus musculus and Rattus norvegicus. The undeveloped territories of the city are characterized by a high total abundance of small mammals, but poor community composition, which is close in its structure to floodplain biotopes. Communities of agrocenoses are also poor, due to elimination of forest species, and characterized by uneven distribution of small mammals among the biotopes. On the whole, the anthropogenic effect of urbanization is manifested in poor composition of communities and changes in the dominance structure. The appearance of the house mouse in the zone of detached housing indicates intensifying urbanization of the territory and ongoing synantropization of the fauna.

Effects of tree retention and woody biomass removal on bird and small mammal communities

Contemporary forest management is increasingly focused on maintaining ecosystem function and services including biodiversity conservation. As a result, harvest guidelines related to retention of live trees and woody biomass (fine and coarse residue arising from harvesting) have been developed to provide benefits for wildlife, but there is much uncertainty on the effectiveness of these guidelines depending on stage of succession, retention levels, and focal taxa. We used an operational-scale, fully replicated factorial experiment to determine the effects of both tree retention (none, dispersed, aggregated) and woody residue harvesting (no removal, 20% retention, all removed) on breeding bird and small mammal communities in aspen forests 7–8 years after harvest. Bird community metric responses showed a clear and consistent positive response to tree retention; both tree retention configurations resulted in higher total abundance, increased diversity, and higher species richness compared to stands with no tree retention. There was no difference in community metrics between the retention configurations and no evidence that early successional species were negatively affected by tree retention. Total abundance of small mammals was lower in clear-cuts compared to tree retention treatments; moreover, clear-cut stands had lower species diversity compared to stands with the aggregated tree retention. There were limited effects of biomass harvest treatments on small mammal communities, likely because actual biomass removal was much lower than experimental targets. Overall, our results provide conclusive evidence on the continued benefits of tree retention on wildlife communities se0ven and eight years post-harvest in regenerating aspen forests.

Maintenance of small mammals using post-harvest woody debris structures on clearcuts: linear configuration of piles is comparable to windrows

Management of post-harvest woody debris structures (e.g., piles and windrows) may help conserve mammal diversity in commercial forest landscapes. A windrow (continuous woody debris) provides a linear habitat to connect patches and reserves of uncut forest and riparian areas to maintain forest-floor small mammals and allow some of their avian and mammalian predators to access and traverse clearcut openings. However, most post-harvest residues are arranged in independent piles of woody debris (separated by 20–30 m, on average) and we asked if a linear configuration of piles would provide similar habitat conditions for small mammals as that achieved by a windrow of continuous woody debris. We tested two hypotheses (H) that piles of woody debris arranged in a linear configuration, on newly clearcut sites, would (H1) enhance (a) abundance of the major small mammal species (Myodes gapperi and Microtus spp.), and (b) total abundance, species richness, and species diversity of the forest-floor small mammal community; compared with dispersed (conventional) treatment of woody debris. H2 predicted that, because of the continuity of habitat, responses of small mammals in windrows would be greater than those in piles of woody debris. Three study areas were monitored in southern British Columbia, Canada, and each had three treatments of woody debris: dispersed, in a linear set of piles, and as a windrow. Forest-floor small mammals were sampled by live-trapping in spring and fall periods from 2010 to 2012. Woody debris in a linear configuration of piles and in windrows enhanced mean abundance of the southern red-backed vole (M. gapperi), total voles, and total abundance of small mammals compared with the dispersed treatment. Small mammal responses were variable between spring and fall periods, but overall mean values ± 95% CIs indicated that abundance of M. gapperi, total voles, and total small mammals were reasonably similar in piles and windrows.

Interacting effects of land use and climate on rodent-borne pathogens in central Kenya.

Understanding the effects of anthropogenic disturbance on zoonotic disease risk is both a critical conservation objective and a public health priority. Here, we evaluate the effects of multiple forms of anthropogenic disturbance across a precipitation gradient on the abundance of pathogen-infected small mammal hosts in a multi-host, multi-pathogen system in central Kenya. Our results suggest that conversion to cropland and wildlife loss alone drive systematic increases in rodent-borne pathogen prevalence, but that pastoral conversion has no such systematic effects. The effects are most likely explained both by changes in total small mammal abundance, and by changes in relative abundance of a few high-competence species, although changes in vector assemblages may also be involved. Several pathogens responded to interactions between disturbance type and climatic conditions, suggesting the potential for synergistic effects of anthropogenic disturbance and climate change on the distribution of disease risk. Overall, these results indicate that conservation can be an effective tool for reducing abundance of rodent-borne pathogens in some contexts (e.g. wildlife loss alone); however, given the strong variation in effects across disturbance types, pathogen taxa and environmental conditions, the use of conservation as public health interventions will need to be carefully tailored to specific pathogens and human contexts.This article is part of the themed issue ‘Conservation, biodiversity and infectious disease: scientific evidence and policy implications’.

Green-tree retention and recovery of an old-forest specialist, the southern red-backed vole (Myodes gapperi), 20 years after harvest

Context Populations of many mammalian species are reduced as a result of clearcutting, despite the concurrent objectives of wood production and conservation of mammal diversity on cutover forest land. To help ameliorate this decline, green-tree retention (GTR) leaves large live trees after harvest to provide mature forest habitat and increase structural diversity of the regenerating stand. Aims To test the hypotheses (H) that, at 20 years after harvest, (H1) abundance, reproduction and survival of the southern red-backed vole (Myodes gapperi), as well as (H2) abundance and species diversity of the forest-floor small mammal community, would increase with the basal area (BA) and density of residual trees after harvest. Methods Small mammals were live-trapped in 2015–16 in replicated clearcut, dispersed retention, aggregated retention, patch cut and uncut forest sites in mixed forests of Douglas fir (Pseudotsuga menziesii var. glauca) and lodgepole pine (Pinus contorta Dougl. var. latifolia) in southern British Columbia, Canada. Key results Mean BA and density of overstory coniferous trees were significantly different at 20 years post-harvest, being higher on patch cut and uncut forest sites than on the clearcut and GTR sites. M. gapperi populations were significantly greater in aggregated retention and uncut forest sites than in the other sites, but demographic parameters were similar among sites, and therefore H1 was partly supported. Mean total abundance of small mammals differed significantly among sites, with the highest overall numbers occurring in the aggregated retention (16.2), clearcut (13.6) and uncut forest sites (11.9). Mean species richness and diversity were highest in the GTR and clearcut sites. Thus, H2 was not supported. Conclusions Recovery of M. gapperi in aggregated retention sites with 10m2 ha–1 BA of residual trees, as a group, occurred at 20 years post-harvest. Implications Aggregated retention of residual trees should help provide some habitat to conserve forest mammals on harvest openings, but successional development up to 20 years post-harvest may be required.

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.

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.

Influence of repeated fertilization and cattle grazing on forest ecosystems: Abundance and diversity of forest-floor small mammals

Intensive silvicultural practices such as pre-commercial thinning (PCT) and repeated fertilization have the potential to provide a diversity of forest habitats and wildlife to meet biodiversity conservation goals while maintaining wood production. Silvopasture combines livestock with trees in some managed forests, but the impact of grazing on biodiversity is unclear. Forest-floor small mammal communities may serve as ecological indicators of changes in forest structure and function, and hence biodiversity. This study was designed to test the hypotheses (H) that in young (13–23years) even-aged lodgepole pine (Pinus contorta) stands, (i) abundance of understory herbaceous vegetation and (ii) abundance and diversity of forest-floor small mammals would be: (H1) enhanced in fertilized stands, and (H2) reduced in stands with cattle grazing. Study areas were located near Kelowna (lightly grazed) and Summerland (heavily grazed) in south-central British Columbia, Canada. Each study area had four pairs of PCT stands thinned to a range of densities with one stand of each pair fertilized four times at 2-year intervals. Herbaceous vegetation and forest-floor small mammal communities were sampled from 1993 to 2002.Mean abundance of total herbs, total grasses, and fireweed (Epilobium angustifolium) all increased dramatically with fertilization in the lightly grazed stands, and hence part (i) of H1 seemed to be supported. Mean total abundance of small mammals was higher in fertilized than unfertilized stands in two years but not overall. Species richness and diversity of small mammals were similar between unfertilized and fertilized stands, and hence part (ii) of H1 was partially supported for abundance, but not for richness or diversity. Lightly grazed fertilized stands had low abundance of Peromyscus maniculatus and Tamias amoenus, but high abundance of Microtus pennsylvanicus, Sorex monticolus, and Sorex cinereus. Phenacomys intermedius and Myodes gapperi also seemed to decline in fertilized stands. Mustela erminea, a principal predator of microtines, was captured more frequently in the lightly grazed fertilized than unfertilized stands.Cattle grazing reduced the abundance of herbaceous vegetation, at least in the fertilized stands at Summerland where they consumed a significant proportion of the biomass, and hence part (i) of H2 was supported. However, this premise did not hold for the unfertilized stands where grazing had little effect on the three plant groups. Part (ii) of H2 was not supported as cattle grazing did not reduce total abundance and species diversity of forest-floor small mammals. Grazing in fertilized stands did limit population fluctuations and dynamics of M. pennsylvanicus and abundance of the two insectivores during certain years. Forest-floor small mammal communities and their myriad ecological functions should be maintained, at least in some years, in those stands intensively managed for wood, biomass, and livestock production.

Riparian and Riverine Wildlife Response to a Newly Created Bridge Crossing

Construction of man-made objects such as roads and bridges can influence wildlife presence and abundance. We investtigated waterbirds, songbirds, anurans, turtles, small mammals, and furbearers along the Ohio River, WV, at a new bridge crossing, a 45-year old bridge, and 1 or 2 islands with no bridge and at 3 distances from the bridge or center point at each site (0 m,100 m, and300 m). We sampled 19 waterbird, 60 songbird, 7 anuran, 5 turtle, 9 small mammal, and 4 furbearer species. Great blue heron (Ardea herodias) abundances were greater at the site with no bridge. Songbird composition differed among sites and between transects under and away from the bridge with higher abundances or association of rock pigeon (Columba livia) and cliff swallow (Petrochelidon pyrrhonota) under the bridges and lower abundances ofCarolinawren (Thryothorus ludovicianus) and common yellowthroat (Geothlypis trichas) under the bridges. Total small mammal abundance, diversity, and richness were lower under the new bridge compared to other sites and distances. We conclude that overall the new bridge is causing minimal relative abundance impacts to wildlife. However, great blue heron abundance may be altered due to noise and activity from the presence of the bridge and minor short-term impacts to some songbirds and small mammals directly under the bridge in the form of habitat conversion, fragmentation, and loss due to removal of vegetation is apparent.

Expansive fire in Mojave Desert shrubland reduces abundance and species diversity of small mammals

Changes in plant community structure and composition of the Mojave Desert in response to greater fire intensity and extent are likely to have strong bottom-up effects on the biological community. The objective of this study was to determine how expansive fire in Mojave Desert impacts small mammal communities across seasons. We sampled small mammals in paired burned (4–5 years post-fire) and unburned areas of Beaver Dam Wash in southwestern Utah. Fire reduced total abundance of small mammals, and species richness and species diversity of the small mammal community. Merriam’s kangaroo rat ( Dipodomys merriami) responded positively to fire (15% greater in burned areas). Long-tailed pocket mouse ( Chaetodipus formosus) and canyon mouse ( Peromyscus crinitus) were 91% and 98% less abundant in burned versus unburned areas. The positive response of Merriam’s kangaroo rat to fire is most likely correlated with their preference for open foraging microhabitat while other species captured prefer greater and more diverse cover. Because the small mammal community has been dramatically affected by fire, it is likely that top-down control of vegetation structure will be dominated by Merriam’s kangaroo rat in burned areas, which may promote more open habitat by limiting the growth of annual and perennial grasses.

Small Mammals and Ground-Dwelling Invertebrates Associated with Active and Controlled Colonies of Black-Tailed Prairie Dogs (Cynomys ludovicianus)

Small mammals and ground-dwelling invertebrates were sampled seasonally on active colonies of black-tailed prairie dogs (Cynomys ludovicianus), Phostoxin®-treated colonies, and non-colonized short-grass prairie to assess potential impacts of Phostoxin® on non-target species in the Texas Panhandle. Eleven species of small mammals were captured. Northern grasshopper mice (Onychomys leucogaster) were more abundant on active prairie dog colonies, whereas abundances of North American deermice (Peromyscus maniculatus) and plains harvest mice (Reithrodontomys montanus) did not differ among treatments. Total abundance of small mammals and relative abundances of other species did not differ among active colonies, Phostoxin®-treated colonies, and non-colonized sites. Ground-dwelling invertebrates were more abundant on active colonies than on Phostoxin®-treated colonies or non-colonized sites. Results of this study indicate that short-term impacts of control of prairie dogs with Phostoxin® on non-target small mammals and ground-dwelling invertebrates is limited, but may be significant for individual species. Additionally, in short-grass prairie ecosystems, vegetative alterations made by prairie dogs may not influence populations of small mammals as much as in tall or mixed-grass prairies. However, active colonies were used more by northern grasshopper mice and ground-dwelling invertebrates, indicating that this habitat is important for these species.

Rodent community structure in tropical forests in south Vietnam: comparative ecology of two dominant species and implications for conservation

Rodents were sampled using the capture-mark-recapture technique along transects in disturbed and undisturbed tropical forest in Cat Tien National Park in south Vietnam. The transects comprised two strata: traps were placed on the ground and in the canopy 2-12 m above the ground. At the main transect, which was 1500 m long and located in undisturbed forest, a total of 438 rodents (173 squirrels and 265 murids) of 12 different species (one Scuridae sp.; 11 Muridae spp.) were marked between January 2005 and January 2006. At this study site and at another undisturbed tropical forest site in the same area, two species dominated: the rat Maxomys surifer (Miller, 1900) and the squirrel Callosciurus flavimanus (Geoffroy, 1831). During the study period we observed no significant difference between the average abundances of the two species (4.67 ± 0.86 and 3.1 ± 0.85 individuals per 100 trap nights, respectively) or between the average proportions of resident squirrels and rats (60.0 ± 24.1 and 62.5 ± 11.5, respectively). The number of squirrels that were permanent residents (i.e. dwelling in the same habitat for 1 year) was eightfold the number of rats that were permanent residents. In addition, there was some synchrony in the daily capture dynamics of squirrels and of rats. We observed no significant difference in the total abundance of small mammals between the arboreal and ground strata. At two disturbed tropical forest sites in the same area, however, no such balance between squirrels and rats was observed, and the density of C. flavimanus was very low. We suggest that the relationship between these two dominant species can act as an indicator of the integrity of tropical forest ecosystems in south Vietnam.

Plant and small mammal diversity in orchard versus non-crop habitats

Abstract This study was designed to determine the abundance and diversity of vascular plant and small mammal communities in a mosaic of orchard and non-crop habitats in an agricultural landscape. Study areas were located at Summerland, British Columbia, Canada where seven replicate habitats: old field, sagebrush, dwarf, and conventional apple orchards, ponderosa pine forest, hedgerow, and riparian were intensively sampled for vascular plant (1999) and small mammal communities (1999–2003). Total plant species sampled included 104 herbs, 26 shrubs, and 9 trees. Mean crown volume index of herbs was similar among sites. Hedgerow and riparian habitats had substantial shrub layers, and the conventional orchard, pine forest, and riparian habitats had the highest biomass of trees. Total mean species richness of plants was similar, but did range from 12.3 species in old field sites to 32.3 species in sage sites. Overall plant species diversity and structural diversity were highest in the sage, hedgerow, and riparian habitats. Total structural diversity was positively related to total species richness and species diversity of vegetation. Mean total abundance of small mammals ranged from 28.1 to 37.0 ha−1 across old field, sage, and riparian habitats compared with a range of 6.2–16.7 animals/ha in the other habitats. Old field and sage habitats generally had the highest levels of species richness and diversity of small mammals, although the other non-crop habitats were similar to these in some years. Structural diversity of vegetation appeared to be a reasonable indicator of biodiversity, at least for vascular plants and small mammals, and should be included in future assessments of diversity in agroecosystems.

Long-term responses of ecosystem components to stand thinning in young lodgepole pine forest: II. Diversity and population dynamics of forest floor small mammals

A variety of silvicultural practices may be used to diversify second-growth forests that have regenerated from clearcut harvesting. These young stands are structurally simple and amenable to practices such as variable-density and conventional thinnings to accelerate ecosystem development. This study was designed to test the hypotheses that (i) abundance and diversity of forest floor small mammals, and (ii) population dynamics (reproduction, recruitment, and survival) of the southern red-backed vole ( Clethrionomys gapperi) would be maintained at levels recorded in old-growth forest, by large-scale thinning to various densities in young lodgepole pine ( Pinus contorta) forest. Replicate study areas were located near Penticton, Kamloops, and Prince George in south-central British Columbia, Canada. Each study area had three stands thinned to densities of ∼500 (low), ∼1000 (medium), and ∼2000 (high) stems/ha, with an unthinned young pine and old-growth pine stand for comparison. Forest floor small mammal communities were sampled intensively in 2000, 2001, and 2002 at 12–14-years after the pre-commercial thinning treatment. Mean total abundance of small mammals was similar among stands with the highest overall numbers recorded in 2002. Mean species richness and diversity of small mammals were similar among stands. Mean abundance of C. gapperi was similar among stands and increased significantly with time. This pattern of abundance of C. gapperi will likely be consistent except perhaps in years of high numbers when productivity of this species may be highest in old-growth forest. Reproduction, recruitment, and early juvenile survival of C. gapperi was similar among stands; Jolly–Seber summer survival was higher in the thinned than unthinned stands with no difference in winter survival among stands. Our results supported hypotheses (i) and (ii) that abundance and diversity of forest floor small mammals and the demographic attributes of C. gapperi populations would be maintained in young managed lodgepole pine stands (thinned or unthinned) at levels recorded in old-growth forest.

Influence of variable retention harvests on forest ecosystems. II. Diversity and population dynamics of small mammals

1 Variable retention harvests in temperate coniferous forests provide various intensities and sizes of disturbance across a gradient, from clear-cutting to single-tree harvesting. These ‘green-tree retention systems’ leave large live trees after harvest (i.e. residual trees) to increase structural diversity of the regenerating stand. It is unclear what effect these harvesting patterns will have on wildlife in general, and small mammals in particular. 2 This study was designed to test the hypotheses that: (i) the abundance and diversity of forest-floor small mammals will decline with lower levels of tree retention; (ii) the abundance, reproduction and survival of Microtus spp. and southern red-backed vole Clethrionomys gapperi populations will decline and increase, respectively, with the basal area and density of residual trees after harvest; and (iii) habitat heterogeneity generated by variable retention harvesting will limit population size of Microtus, thereby reducing feeding damage to tree seedlings planted on harvested areas. 3 Small mammals were intensively live-trapped from 1996 to 1999 in replicated clear-cut, single seed-tree, group seed-tree, patch-cut and uncut forest sites in mixed natural forests of Douglas fir Pseudotsuga menziesii–lodgepole pine Pinus contorta in southern British Columbia, Canada. The seed-tree harvesting system leaves a few wind-firm seed trees standing singly, or in groups, to provide seed to regenerate an area naturally. The patch-cut system harvests timber from small (< 1-ha) units dispersed over a given area of forest. 4 Contrary to hypothesis (i), the mean total abundance of small mammals was similar among sites, and mean species richness and diversity of small mammals was lowest in the uncut forest but similar across the other four treatments. 5 The overall mean abundance (ha−1) of Microtus spp. was higher on clear-cut (11·3) sites than single seed-tree (6·0), group seed-tree (3·9), patch-cut (1·8) or uncut forest (0·1) sites. Overall mean abundance (ha−1) of C. gapperi was similar in uncut forest (16·2) and group seed-tree (10·0) sites, which were both higher than patch-cut (6·4), clear-cut (4·2) or single seed-tree (2·7) sites. 6 The recruitment of new Microtus spp. differed significantly among sites, declining from clear-cut to uncut forest. The recruitment of C. gapperi exhibited the opposite trend. The mean number of successful pregnancies was similar among treatments for Microtus spp. but for C. gapperi was highest in uncut forest, group seed-tree and patch-cut sites. The survival of each vole species was similar across treatment sites. 7 Hypothesis (ii) was supported. The mean abundance of Microtus spp. was inversely, and that of C. gapperi positively, related to mean basal area and density of residual trees after harvest. The mean abundance of Microtus spp. was also inversely related to percentage cover and crown volume index of residual trees, and positively related to number of lodgepole pine cones (seeds) in logging debris. 8 In terms of hypothesis (iii), vole feeding damage to planted lodgepole pine seedlings appeared highest in the patch-cut sites during the 1997–98 and 1998–99 overwinter periods, and appeared to have been caused mainly by C. gapperi rather than Microtus spp. 9 The group seed-tree and patch-cut systems achieved both aims of C. gapperi persistence and prevention of Microtus outbreaks. These harvesting methods are as good for overall small mammal abundance, species richness and diversity as any other.

The impact of buffer strips and stream-side grazing on small mammals in southwestern Wisconsin

The practice of continuously grazing cattle along streams has caused extensive degradation of riparian habitats. Buffer strips and managed intensive rotational grazing (MIRG) have been proposed to protect and restore stream ecosystems in Wisconsin. However, the ecological implications of a switch from traditional livestock management to MIRG or buffer strip establishment have not been investigated. Differences in small mammal communities associated with riparian areas on continuously grazed and MIRG pastures, as well as vegetative buffer strips adjacent to row crops, were investigated in southwestern Wisconsin during May–September 1997 and 1998. More species (mean of 6–7) were found on the buffer sites than on the pasture sites (mean of 2–5). Total small mammal abundance on buffer sites was greater than on the pastures as well; there were 3–5 times as many animals on the buffer sites compared to the pasture sites, depending on year. There were no differences in species richness or total abundance between MIRG and continuously grazed pastures in either year. Total small mammal abundance was greater near the stream than away from the stream, regardless of farm management practice but there were no differences in species richness. Buffer strips appear to support a particularly rich and abundant small mammal community. Although results did not detect a difference in small mammal use between pasture types, farm-wide implications of a conversion from continuous to MIRG styles of grazing may benefit small mammals indirectly by causing an increase in the prevalence of pasture in the agricultural landscape.