Habitat fragmentation and predation: Experiments with bank voles (Myodes glareolus) and least weasel (Mustela nivalis nivalis)

Abstract

Habitat loss and fragmentation are the main causes for innumerable population declines and species having become threatened or extinct. Habitat fragmentation inevitably affects behaviour and social interactions of individuals. These are likely to form an essential part of the mechanism behind observed population declines. Predator - prey interaction is strong factor shaping population viability and individual numbers and it is thought to change after habitat loss and fragmentation. The prediction is that specialized predators, dependent on a certain habitat type, should be more vulnerable to habitat loss compared to generalist predators, but habitat fragmentation effects are unknown. In this presentation, I summarize the results from our predator - prey experiments conducted in experimentally fragmented habitat, created in to 0.25 ha small mammal proof enclosures. Enclosures consisted of either non-fragmented (one patch) or fragmented (four patches) habitat of the same total area surrounded by low vegetation matrix. We have been measuring the fragmentation effects on behaviour and fitness of prey species the bank vole (Myodes glareolus) and predator species the least weasel (Mustela nivalis nivalis) in a series of experiments. We found that fragmentation led to increased matrix use in male voles and weasels, when resources were distributed into separate habitat patches. Small habitat fragments kept female bank voles closer to their nest where they were better able to protect pups against nest predators, infanticidal males. However, this did not affect the number of offspring recruited per female 1. Mammalian predator odor, a cue about increased predation risk in the habitat patches, decreased vole movements and voles directed movements towards matrix where the avian predation risk was higher 2. During high avian predation pressure, survival of male voles was poorer in fragmented habitat. Especially, males who moved most and spent time on open and risky matrix during radio -tracking were more likely to be depredated. Weasels killed more voles in the continuous habitat, which provided them safe hunting habitat from avian predators. However, this was only during autumn, when the kill rate was also higher due to cold weather 3. To conclude, habitat fragmentation has direct survival and fitness consequences for individuals and it changes species interactions, but direction of these effects depend on fragmentation types and duration and scale of experiments.

1 Haapakoski M. et al. Infanticide effects on behavior of the bank vole (Myodes glareolus) in the fragmented breeding habitat. Behav Ecol Sociobiol 2015; 69: 49–59. 2 Haapakoski M. et al. Conservation implications of change in antipredator behavior in fragmented habitat: Boreal rodent, the bank vole, as an experimental model. Biol Conserv 2015; 184: 11–17. 3 Haapakoski M. et al. Mammalian predator-prey interaction in a fragmented landscape: Weasels and voles. Oecologia 2013; 173: 1227–1235.