Female Wild House Mice Research Articles

Impact of male presence on female sociality and stress endocrinology in wild house mice (Mus musculus domesticus)

In group living animals, reproductive competition plays an important role in shaping social relationships and associations among female group members. In this study, we investigated the impact of male presence on the development of female-female competition and female sociality in groups of female wild house mice, using physiological and behavioral parameters. We predicted that, by eliciting intra-sexual competition, males influence social relationships among female group members and thus affect female associations to potential cooperation partners. To test this hypothesis we compared stress hormone production, the frequency of agonistic interactions, social hierarchies and social partner preferences in groups of unrelated, unfamiliar females in the absence and presence of males. Our results revealed no indication that the introduction of males into all-female groups of wild house mice elicited increased competition among female group members, neither on the physiological nor on the behavioral level. We found no effect of male presence on female glucocorticoid secretion, aggression, dominance hierarchies or on the females' sociability. Females thus seem not to intensely compete over access to males. This female ability to behaviorally and physiologically deal with even previously unfamiliar same-sex group members may be an important feature of female house mouse societies. In fact, it could be a necessary prerequisite to establish cooperative relationships between females in the context of reproduction, such as communal nursing of young.

Exploration and risk assessment in female wild house mice ( Mus musculus musculus) and two laboratory strains

In an evolutionary prospective, it is possible that female mice have a differential perception of novel events than male mice and use a different behavioural strategy for risk assessment. However, female mice are less studied than male mice in behavioural tests of emotional reactivity. The aim of the present study was to investigate how wild-derived female house mice differ from domesticated female mice in their risk assessment strategy. A total of 46 adult female mice, 14 BALB/c, 16 C57BL/6 and 14 Wild mice were tested in the Concentric Square Field (CSF), Open Field (OF) and Elevated Plus Maze (EPM) at three consecutive days. Parameters from all three tests were categorized according to their relevance to activity, exploration, approach–avoidance and use of open areas–shelter. Principal Component Analysis (PCA-SIMCA) of the animals' behaviour in the CSF arena was performed both for females alone and in comparison with earlier findings in male mice under the same test conditions. The results clearly show that female wild mice had a higher avoidance of open areas than the laboratory strains. There was also a trend indicating differences in exploration and approach–avoidance between female Wild and the laboratory strains. The multivariate test, CSF, was able to detect differences between Wild and laboratory strains in three (exploration, approach–avoidance, open–shelter) of the four functional categories measured. Wild female mice also had a higher frequency of rearing and grooming and a lower duration in the corridors in the CSF. Clear strain differences were found between BALB and C57BL in all tests where BALB generally had higher risk assessment and lower risk taking than C57BL. No general sex differences were found, however the sex differences were greater in Wild mice compared to the laboratory strains.

Pre-reproductive alliance formation in female wild house mice ( Mus domesticus ): the effects of familiarity and age disparity

Female house mice (Mus domesticus) are known to perform communal breeding more often with kin than with non-kin partners. When mice are grouped in semi-natural enclosures, related females develop pre- reproductive alliances more frequently than unrelated ones. However, little is known about the behavioural mechanisms and the factors promoting kin preferential cooperative associations in female mice. Here we evaluate the relative importance of familiarity and age disparity on the pre-reproductive development of agonistic behaviour and spatial associations within groups of three related females, freely interacting in semi-natural indoor enclo- sures. We found that familiarity clearly promoted female alliance formation by reducing aggression and enhancing spatial cohabitation, while genetic relatedness per se did not alleviate the effects of unfamiliarity on female grouping. Older sisters clearly dominated younger ones, even if they had lower body weights, or if they had to confront two allied littermate sisters. Hence, our findings corroborate previous findings on familiarity as a proxy for kin-preferential alliance formation in female mice. More- over, we observed a strong impact of age stratification on female aggression-mediated dominance development. We suggest that this age effect could be expected from a queuing-for-reproduction view of younger house mouse females.

Short-term early exposure to pups alters infanticide in adulthood in male but not in female wild house mice (Mus domesticus).

Male and female wild house mice (Mus domesticus) were allowed to remain in the cage of their parents until 30-35 days of age. When a second litter was delivered, the first litter was exposed to the younger pups for 2-10 days. In adulthood the male and female mice that had been exposed to pups as juveniles and an additional group that had cohabitated with their parents for the same length of time but were not exposed to pups were tested for infanticidal behavior. The frequency of infanticide by the adult female mice was not significantly different (55% vs. 70%, respectively). In contrast, the adult males that were exposed to pups as juveniles were significantly less likely to kill young in adulthood when compared with males that were not similarly exposed (35% vs. 80%, respectively). These data further demonstrate the strong influence of experience on the expression of infanticide by male mice and its relative unimportance to the expression of female infanticide.

Short-term early exposure to pups alters infanticide in adulthood in male but not in female wild house mice (Mus domesticus).

Short-term early exposure to pups alters infanticide in adulthood in male but not in female wild house mice (Mus domesticus).

Are nests built for fun? Effects of alternative activities on nest-building by wild house mice

Male and virgin female wild house mice, Mus musculus , aged 8 to 14 weeks, of the first generation bred in captivity, built nests of cotton wool in an ambient temperature of 23°C. Controls were each in a small cage (750 cm 2 ). Others had one of the following: (i) balsa wood to chew; (ii) a wheel in which to run; (iii) an additional small cage connected to the home cage; or (iv) a large cage (3600 cm 2 ) in which to explore. The cotton pulled in, and the quality of the nest built, were recorded on 2 successive days. No difference was observed between sexes or between days. The balsa wood had no effect. All other treatments led to a reduction in both cotton-pulling and nest-building. The large cage had the greatest effect. There was always a high positive correlation between amount of cotton pulled and nest quality. Nest-building resembles exploration in increasing the stimulation received and in being rewarding. The present experiments show exploration by mice in a warm environment to compete with nest-building and to have priority over it. Some nest-building may come in the general category of play.