Dynamics of Small Mammal Populations: A Review

Abstract

An understanding of population dynamics requires explanations for both the patterns of fluctuations and the densities at which they occur. To identify the causal mechanisms involved, we need to examine the environmental factors that impinge upon the population, the integrative responses of individuals that link changes in the environment to individual performance, and the population changes that occur as a result of shifting individual performances. A review of the literature on small mammals, mostly rodents, suggests that average population levels are largely determined by a balance of the positive effects of resources and 'the negative effects of enemies and that the strengths of these effects vary from habitat to habitat. Seasonal patterns of population change occur each year largely because of seasonal breeding; differences among years occur because of shifts in weather, resources, and enemies. Multiannual patterns (cycles) may occur because of time lags in responses to environmental change or because of combinations of nonlinear responses to density. The volatility of population density appears to vary directly with reproductive potential and inversely with the strength of density-dependent recruitment. A general approach for determining which factors are the mO,st important for any particular population requires a mechanistic, multiple-factor view of population dynamics. Multiple-factor experiments can and should be used to test our understanding of the complex web of cause-and-effect relationships that influence the density of small mammals. 831 D. R. McCullough et al. (eds.), Wildlife 2001: Populations Environmental Factors ~ Physiological-Behavioral ~ Individual Performance Responses t Population Change / Fig. 1. Model of the relationships among environmental factors, individual responses, individual performance, and popUlation change.

Nitrogen and Carbon Concentrations in the Stomach Content of Bank Voles (Myodes glareolus). Does Food Quality Determine Abundance?

“…Small mammalian herbivores such as the bank vole have high energy metabolism and turnover of essential nutrients. This suggests that small mammalian herbivores face a relative shortness of N and that this situation may be a potential cause for variations in population density between seasons and years (Hansson 1987, 1995, Batzli 1992, Hambäck et al 2002, Wereszczynska et al 2007. Protein requirement is a result of two components a) endogenous urinary excretion and b) fecal loss.…”

Effects of regime shifts on the population dynamics of the grey-sided vole in Hokkaido, Japan

“…Rodent cycles represent an enigma which has been puzzling many ecologists since Elton (1924). At least 22 hypotheses have been proposed on how the cycles are generated (Batzli 1992). Many of the hypotheses try to explain the cycle using a single factor and they have been tested by experiments in the field.…”

Nesting Behavior, Provisioning Rates, and Parental Roles of Ferruginous Hawks in New Mexico

“…The role of predators in controlling prey populations has been the focus of debate in the ecological literature for some time (Edminster 1939, Huffaker 1958, Errington 1963, Paine 1974, Hansson and Henttonen 1988, Hanski et al 1991, Batzli 1992, Stenseth and Ims 1993, Norrdahl 1995, Norrdahl and Korpimäki 1995, Korpimäki and Krebs 1996, Krebs 1996, Stenseth et al 1996. Other studies (Keith 1990, Krebs et al 1995, Selas et al 2002 have suggested that other factors such as food availability/ quality determine prey abundance, which may in turn drive predator numbers.…”