Rodents, cowpox virus and islands: densities, numbers and thresholds (original) (raw)
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Population cycles and outbreaks of small rodents: ten essential questions we still need to solve
Oecologia
Most small rodent populations in the world have fascinating population dynamics. In the northern hemisphere, voles and lemmings tend to show population cycles with regular fluctuations in numbers. In the southern hemisphere, small rodents tend to have large amplitude outbreaks with less regular intervals. In the light of vast research and debate over almost a century, we here discuss the driving forces of these different rodent population dynamics. We highlight ten questions directly related to the various characteristics of relevant populations and ecosystems that still need to be answered. This overview is not intended as a complete list of questions but rather focuses on the most important issues that are essential for understanding the generality of small rodent population dynamics.
Population dynamics of house mice without mammalian predators and competitors
New Zealand Journal of Ecology
Mesopredator and competitor release can lead to population increases of invasive house mice (Mus musculus) after larger introduced mammals are controlled or eradicated. In New Zealand, mammal-resistant fences have enabled multi-species mammal eradications in order to protect indigenous species. When house mice are the only mammals remaining in these biodiversity sanctuaries, they may reach a high population density, with potential consequences for their indigenous prey. We studied mouse populations in the absence of other mammals for 5 years at mammal-resistant fenced forest sites at Maungatautari, Waikato. We used spatially explicit capture-recapture (SECR) to estimate mouse population density quarterly in two independently fenced sites, with contrasting levels of mouse management that were switched halfway through the study. In the absence of mouse control, mouse population density reached 30-46 ha-1 at one site each year after summer breeding, and 23 ha-1 at the other site. Mouse tracking rates in inked footprint tunnels were positively related to numbers of mice captured in each session, but not significantly to mouse density. The highest mouse densities were similar to estimates in New Zealand forest and alpine ecosystems after mass seeding (masting) events, but lower than estimates in another sanctuary and on some islands lacking larger terrestrial mammals. We suggest that in the absence of competition and predation from other mammals, food limitation may have prevented mouse populations from attaining very high densities in this mainland forest location.
Spatiotemporal variation in drivers of parasitism in a wild wood mouse population
Host-parasite interactions in nature are driven by a range of factors across several ecological scales, so observed relationships are often context-dependent. Importantly, if these factors vary across space and time, practical sampling limitations can limit or bias inferences, and the relative importance of different drivers can be hard to discern.We collected a replicated, longitudinal dataset of >1000 individual wood mice (Apodemus sylvaticus) encompassing 6 years of sampling across 5 different woodland sites to investigate how environmental, host and within-host factors determine infection intensity of a highly prevalent gastrointestinal nematode, Heligmosomoides polygyrus.We used a Bayesian modelling approach to further quantify if and how each factor varied in space and time. Finally, we examined the extent to which a lack of spatially or temporally replication (i.e., within single years or single sites) and single (cross-sectional) versus repeated (longitudinal) sampling of...
Emerging Infectious Diseases, 1997
Emerging Infectious Diseases Dispatches A new acute respiratory illness, hantavirus pulmonary syndrome (HPS), was first documented in May 1993 in New Mexico (1). The death rate was initially more than 90% (1,2) and is now approximately 50% (3). Serologic surveys indicated positive reactions with previously known hantavirus antigens but not with any agents usually associated with severe respiratory illness (2). Four distinct serotypes of hantaviruses, which are carried by rodents, were known before 1993 (2). The virus causing HPS in the Four Corners area, Sin Nombre virus (SNV), represents an unusual fifth serotype that affects the lungs and has a high death rate (1,4). During the 1993 outbreak, rodents were trapped in and near homes with confirmed SNV cases and tested for hantavirus antibodies (1). Peromyscus maniculatus (deer mouse) was the most common rodent captured and had the highest antibody prevalence. Average prevalence was 30.4% (0% to 51.3% range) for 813 P. maniculatus captured at 21 sites (1). P. maniculatus is the only species of mouse on four of the five islands that make up Channel Islands National Park; Santa Cruz Island also has populations of Reithrodontomys megalotis. Channel Islands National Park (Figure 1) has been monitoring deer mouse populations on Santa Barbara Island for 19 years (recorded data are incomplete) and on San Miguel and Anacapa Islands since 1993 (5; C. Schwemm, pers. comm.). Concern for the health of persons trapping mice and others on the islands prompted testing of
Journal of Applied Ecology, 2000
1. A stochastic individual-based model for simulating the dynamics of an infectious disease in sympatric red and grey squirrel populations is described. The model simulates the spread of parapoxvirus between squirrels in fragmented populations based on the dispersal of infected animals, the probability of encounters between individuals, exposure to the virus and subsequent mortality.2. The disease model was integrated with a spatially explicit population dynamics model that simulated red and grey squirrel populations in real landscapes, using habitat information held in a geographical information system. Latin hypercube sampling was used to create a range of realistic life-history and infection scenarios and the model was used to investigate the dynamics of red and grey squirrels in Norfolk between 1966 and 1980.3. The model predicted that parapoxvirus, like interspecific competition, could have led to the extinction of the red squirrel in Norfolk. The results suggest that the red squirrel–grey squirrel–parapoxvirus interaction represents a system of apparent competition mediated by an infectious agent, as seen in other interactions between resident and exotic species.4. The need for further epidemiological research on the virus is emphasized. We believe that the combined effects on disease transmission of habitat, behaviour and grey squirrels acting as reservoir hosts will lead to a patchy prevalence and sporadic incidence of parapoxvirus disease in red squirrels and a more rapid local replacement by grey squirrels.5. These results have implications for conservation management of the red squirrel in the UK. Schemes in which animals are translocated or given supplementary feeding may enhance disease spread by bringing infected animals into contact with others.
2017
Baláž, I., Jakab, I., Tulis, F., Ambros, M., 2016. Spatial density of two sympatric species Yellow-necked Mouse Apodemus flavicollis and Bank Vole Clethrionomys glareolus in different environment. Folia Oecologica, 43: 121–128. The impact of two different environments (climax forest and glade) on spatial density of Yellow-Necked Mouse and Bank Vole was studied during the years 2011–2013. Species range (95% Kernel) of both species was calculated based on data obtained from live traps placed in trap grids. Eight levels of density probability that surround regions of constant probability density were used to define (i) activity centres of observed species and (ii) areas that tended to be of rather peripheral interest. Results suggest that glade with rich herbal-ground cover represented significantly more suitable habitat, as well as habitat richer in resources for Bank Vole in comparison to climax forest. In contrary, Yellow-necked Mouse had provably the highest spatial density in clim...