Population Dynamics Of Small Mammals Research Articles

Hantavirus in Montana deer mouse populations: preliminary results.

Dynamics of small mammal populations and the prevalence of antibodies for hantavirus were determined in six locations in central and western Montana (USA). Eighteen live-trapping grids were trapped monthly from June through September 1994. Deer mouse (Peromyscus maniculatus) populations ranged from 0 to over 90 on one-hectare grids. Our bleeding technique had no apparent effect on survival of deer mice. Deer mice, meadow voles (Microtus pennsylvanicus), and sagebrush voles (Lagurus curtatus) were seropositive. Thirty-eight (8%) (range, 0% to 30%) of 471 deer mice were seropositive for hantavirus antibodies. Seropositive mice were older and had lower monthly survival rates than seronegative deer mice. We found no relationship between prevalence of hantavirus antibodies and population density.

The Ecology of Woodland Creation.

To What Extent Can We Recreate Woodland? (J. Spencer). Planning and Designing New Woodlands for People (M. Sangster). New Woodlands in the Landscape (S. Bell). Biogeography and Woodland Design (I. Spellerberg). Vegetation Classification Systems as an Aid to Woodland Creation (J. Rodwell G. Patterson). Soils and Restoration Ecology (A. Moffat G. Buckley). Soil Biotic Communities and New Woodland (J. Harris T. Hill). Creating Woodlands: To Plant Trees or Not? (R. Harmer G. Kerr). Introduction of Plants and Manipulation of Field Layer Vegetation (J. Packham, et al.). Invertebrate Conservation and New Woodland in Britain (R. Key). Bird Populations in New Lowland Woods: Landscape, Design and Management Perspectives (R. Fuller, et al.). Population Dynamics of Small Mammals in New Woodlands (J. Flowerdew R. Trout). Do Woodland Mammals Threaten the Development of New Woods? (R. Gill, et al.). Ecological Planning in New Woodlands (R. Ferris-Kaan). Indexes.

The population dynamics of small mammals living in set‐aside and surrounding semi‐natural and crop land

Small mammals were found on set‐aside and surrounding farmland. Wood mice showed a different pattern of demography at two sites, with higher densities, greater survival, heavier weights and longer breeding seasons at Aldroughty than at Newburgh. These differences were thought to be due to a difference in habitat productivity at the two sites. Field voles showed less of a difference in population dynamics between the two sites, and both species of vole maintained populations at low densities.

Population dynamics of helminth parasites in wild and laboratory rodents

AbstractThis paper reviews the host‐helminth interactions that are of importance in regulating both the abundance of helminth parasites of rodents and the host population abundance. Parasite density has an effect on the ability of individual parasites to grow, reproduce and survive within the definitive host, and it also influences the ability of the infected host to survive and reproduce. The severity of the impact of such density‐dependent responses is related to the pattern of parasite distribution within the host population. The potential of helminth parasites to regulate the abundance of a small mammal population is illustrated using an experimental example. Areas identified for further research include (i) an investigation of the relative importance of parasite density‐dependent effects on parasite and host survival and reproduction for specific host‐helminth associations; (ii) more research into the impact of helminth density on host reproduction; and (iii) research into the impact of helminths on the population dynamics of small mammal populations using field and laboratory experiments designed to assess the relative importance of helminths in regulating the abundance of their host populations.SummaryIn this paper we have considered parasite density as an important determinant of parasite and host population dynamics. Because the relative impact of density on different population processes will differ for different helminths, researchers interested in accounting for temporal dynamics of a specific parasite will need to investigate the density‐dependent processes involved in the life cycle of that helminth.Although interactions between the population biology of both the host and helminth parasite are of fundamental importance to the population dynamics of the parasite, they also are important in determining the population dynamics of the infected host population. Because helminths, by definition, must have an impact on the ability of the host population to survive or reproduce they, therefore, also have the potential to regulate the abundance of the host population (Anderson & May, 1978; Anderson, 1979). More research is needed on the effect of parasite density on the rate of reproduction of infected hosts. Finally, given recent theoretical and experimental evidence that parasites can regulate mammal populations, much work is needed to determine conditions when this actually occurs in the field.

Population Dynamics of Small Mammals in Farmstead Shelterbelts

Various aspects of the population dynamics of Sorex cinereus, Blarina brevicauda, Clethrionomys gapperi, Microtus pennsylvanicus , and Peromyscus leucopus were studied for 27 months in Minnesota farmstead shelterbelts. Total numbers of individuals of all species combined were greatest in summer and autumn; species-specific peaks in seasonal abundance were partially attributed to juvenile recruitment. Percentages of breeding adult females were similar in the three species of cricetids, but relatively fewer adult males of M. pennsylvanicus were in reproductive condition than in other cricetids. Young cricetids tended to be transient compared to adults; in P. leucopus , young females were more likely to be residents than young males. Adult transients weighed less than adult residents in both M. pennsylvanicus and P. leucopus . Distances moved within shelterbelts did not vary among species; movements between shelterbelts occurred most often in B. brevicauda but never in P. leucopus . Probabilities of recapture over months were comparable among species. Aspects of the population dynamics of the five species in these man-made habitats generally were similar to those reported by studies in less modified environments. Because of the importance of shelterbelts to populations of C. gapperi and P. leucopus and to other species of wildlife, efforts should be made to preserve these wooded islands in intensely-farmed regions of the Upper Midwest.

Behavioraldominance and its relationship to habitat patch utilization by the hispid cotton rat (Sigmodon hispidus)

The influence of spacing behavior on population dynamics of small mammals has often been suggested. Patterns of habitat patch occupancy elucidated in previous studies of cotton rats (Sigmodon hispidus) suggested that spacing behavior might be an important factor in population regulation of this species. In this study, habitat selection experiments in enclosures indicated that cotton rats preferred patches with shrubs present. However, this preference was density-dependent with more equal habitat occurrence at higher densities. Two experimental patchy habitats were created in open fields and were composed of alternating 0.2-ha squares with overhead shrub cover for possible predator protection present (preferred habitat) and with shrub cover removed by mowing. It was hypothesized that subordinate animals would occupy less preferred patches, thus exhibiting reduced fitness. Animals captured in patches with shrubs were larger, moved greater distances, and were in reproductive condition more often than animals in patches without shrubs. There was only a slight difference in survival rates between patch types, however. Behavioral encounters between animals captured in the two patch types resulted in animals from patches with shrubs exhibiting significantly more dominance-type behavior and winning encounters significantly more often than those from patches without shrubs. Results suggested that spacing behavior is important in regulating habitat occurrence of cotton rats. Dominant animals were able to occupy preferred habitat patches. It seems that dominance serves to ameliorate the increase in population density/unit area in good habitat by influencing the movement of subordinates into less preferred habitat. Normal mortality factors then decrease density in all habitats, whereupon density increases begin in good habitat and again spread into poorer habitat types.

Evaluation of the role of small mammals in grassland ecosystems: A modelling approach

Development of a grassland ecosystem simulation model quantifying mammal interaction with other ecosystem components indicates their influence on community structure and function. The approach has been to: (1) identify potential areas of small mammal interaction with system function; (2) quantify the interactions; (3) construct a model representing these interactions; (4) synthesize quantitative information on small mammal interactions with auxiliary information to obtain a mathematical representation of the major functional aspects of an ecosystem; and (5) simulate the ecosystem to estimate overall influence of small mammals. To facilitate the identification of potential influence, six small mammal functional groups and three major ecosystem components were specified. Small mammal groups include three feeding categories: (1) herbivore, (2) carnivore, and (3) granivore; and three behavioral categories: (1) soil mover, (2) food storer, and (3) builder. The three ecosystem components include: (1) abiotic, (2) primary producer, and (3) consumer-decomposer. A six by three matrix was formed with rows representing the six small mammal groups and columns representing the three ecosystem components. Each compartment of the matrix indicates potential influences of the small mammal group on the ecosystem component. Simulations indicate that two small mammal activities have greatest impact on other ecosystem components. Upward translocation of soil has a significant positive effect on both percent bare surface soil and quantity of nitrogen in the top soil layer; and consumption of arthropods has a significant effect on arthropod biomass dynamics. Even with extremely high small mammal densities direct consumption has an insignificant effect on primary production. Based on indices quantifying total impact of small mammals, the hypothesis that grassland ecosystem structure can be fundamentally altered by changes in the small mammal community is tentatively rejected. Ecosystem function appears to be affected by relatively small fluctuations in small mammal density and by certain changes in composition of the small mammal community. Routes and rates of material flow within an ecosystem are influenced by small mammals, producing subtle but quantitative changes in ecosystem dynamics which are directly or indirectly a function of small mammal population dynamics. Therefore, the hypothesis that grassland ecosystem function is responsive to changes in the small mammal community cannot be rejected.