Failure of reproduction in female alpine marmots after territory take-overs by males [Echec de la reproduction chez les marmottes alpines femelles après conquëte de leur territoire par des mâles].

Résumé

We studied free-ranging alpine marmots (Marmota marmota) over a period of 14 years in the National Park of Berchtesgaden, Germany. Alpine marmots lived in a social groups with only one reproducing dominant female per group. Alpine marmots lived in a social group with only one reproducing dominant female per group. During the study period 13 territory take-overs by male immigrants occured after the mating season. In these groups, there were no juveniles emerging above ground. However, up to nine of the 13 dominant females from groups with male take-over showed clear signs of pregnancy, five have enlarged nipples or moulted late in the year and four had progesterone levels similar to those of successfully reproducing femalessampled in the same time interval. Furthermore, the body mass at emergence from hibernation of females from groups with the subsequent male take-overs (n=7) did not differ from the body mass of successfully reproducing females (n=79, p=0.67).These data suggest that new territorial males prevent that females produce surviving young sired by their predecessors, either by infanticide or block of gestation. such male behaviour is adaptative because non-parous females save the energetic cost of warming juveniles during winter, therefore emerge with higher body mass in the following spring (p < 0.01) and hence have higher chances for reproduction.