Differential behavioural and endocrine responses of common voles (Microtus arvalis) to nest predators and resource competitors

Abstract

BackgroundAdaptive behavioural strategies promoting co-occurrence of competing species are known to result from a sympatric evolutionary past. Strategies should be different for indirect resource competition (exploitation, e.g., foraging and avoidance behaviour) than for direct interspecific interference (e.g., aggression, vigilance, and nest guarding). We studied the effects of resource competition and nest predation in sympatric small mammal species using semi-fossorial voles and shrews, which prey on vole offspring during their sensitive nestling phase. Experiments were conducted in caged outdoor enclosures. Focus common vole mothers (Microtus arvalis) were either caged with a greater white-toothed shrew (Crocidura russula) as a potential nest predator, with an herbivorous field vole (Microtus agrestis) as a heterospecific resource competitor, or with a conspecific resource competitor.ResultsWe studied behavioural adaptations of vole mothers during pregnancy, parturition, and early lactation, specifically modifications of the burrow architecture and activity at burrow entrances. Further, we measured pre- and postpartum faecal corticosterone metabolites (FCMs) of mothers to test for elevated stress hormone levels. Only in the presence of the nest predator were prepartum FCMs elevated, but we found no loss of vole nestlings and no differences in nestling body weight in the presence of the nest predator or the heterospecific resource competitor. Although the presence of both the shrew and the field vole induced prepartum modifications to the burrow architecture, only nest predators caused an increase in vigilance time at burrow entrances during the sensitive nestling phase.ConclusionVoles displayed an adequate behavioural response for both resource competitors and nest predators. They modified burrow architecture to improve nest guarding and increased their vigilance at burrow entrances to enhance offspring survival chances. Our study revealed differential behavioural adaptations to resource competitors and nest predators.

Hormonal adjustments to urban conditions: stress hormone levels in urban and rural populations of Apodemus agrarius

“…Other than the stressful effect of predators, another explanation of our results is antagonistic contact between the studied rodent and other species of small mammals, including resource competitors (other species of mice or voles) and nest predators, i.e. shrews (Liesenjohann et al 2013). In the rural areas the pressure from competitive species is relatively high because the studied species accounted for only 38% of all captured small mammals.…”

Wheel access has opposing effects on stress physiology depending on social environment in female prairie voles (Microtus ochrogaster)

“…A reasonable prediction might be that the paired group should have traveled approximately twice the distance than that of the isolated group, similar to what is observed in single-vs. pair-housed rats (Greenwood and Fleshner, 2011). Therefore, among paired animals, the limited availability of an exercise wheel might have represented a stressor (Liesenjohann et al, 2013). On the other hand, for isolated animals that did not have a sibling to compete with, the exercise wheel would not represent a stressor.…”

Experience of social density during early life is associated with attraction to conspecific odour in the common vole (Microtus arvalis)

“…After another 20 days, parental females and their weaned offspring were removed from the enclosures by live trapping. Offspring, the test animals, had experienced close contact with their nestling siblings and their mothers, but in the high contact treatments potentially had contacts to other adult females and other juveniles since vole females can nest communally (Boyce & Boyce, 1988b), can visit each other's nests (Boyce & Boyce, 1988b; Liesenjohann et al., 2013) or may meet at their first days of leaving the nest and experiencing the environment.…”