Suppressed breeding in the field vole (Microtus agrestis): an adaptation to cyclically fluctuating predation risk

• Published in: Behavioral Ecology
• Main Authors: Koskela, Esa, YlÖnen, Hannu
• Format: Text
• Language: English
• Published: Oxford University Press 1995
• Subjects: Articles; Fennoscandia
• Online Access: http://beheco.oxfordjournals.org/cgi/content/short/6/3/311; https://doi.org/10.1093/beheco/6.3.311

The densities of microtine rodents and their main predators, small mustelids, fluctuate synchronously in 3–5-year cycles in central and northern Fennoscandia. Predation by small mustelids has been suggested as one of the driving forces in microtine cyclicity, causing deep synchronous declines of several vole species. We studied experimentally the effects of small mustelids on mating behavior, foraging, and breeding in nonwintered field voles ( Microtus agrestis ) originating from a cyclic population. By using mustelid odors, we simulated a crash phase environment with high predation risk for breeding pairs of voles. In our experiments, 87% of the female field voles suppressed breeding when exposed to mustelid odors. Both female and male behavior changed, and no mating behaviors were observed under the simulated predation risk. Weights of both sexes decreased when exposed to mustelid odor, probably due to decreased foraging; weights of the control females increased due to pregnancy; and no weight changes occurred in control males. Decreased breeding and foraging possibilities under high predation pressure may form the basis for the ultimate explanation for breeding suppression. There are at least two different mechanisms for breeding suppression: either mating does not take place or malnutrition in females does not' allow breeding to occur. Delayed breeding under high risk of predation, for whatever reason, could increase the probability of individuals, especially that of the females, to survive over the crash to the next, safer breeding season when their young would have better possibilities to survive.