Highly competitive reindeer males control female behavior during the rut.

Guillaume Body,Mauri Nieminen,Robert B Weladji,Øystein Holand,Cheryl S Rosenfeld

doi:10.1371/journal.pone.0095618

Guillaume Body, Mauri Nieminen + Show 3 more

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https://doi.org/10.1371/journal.pone.0095618

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Abstract

During the rut, female ungulates move among harems or territories, either to sample mates or to avoid harassment. Females may be herded by a male, may stay with a preferred male, or aggregate near a dominant male to avoid harassment from other males. In fission-fusion group dynamics, female movement is best described by the group’s fission probability, instead of inter-harem movement. In this study, we tested whether male herding ability, female mate choice or harassment avoidance influence fission probability. We recorded group dynamics in a herd of reindeer Rangifer tarandus equipped with GPS collars with activity sensors. We found no evidence that the harassment level in the group affected fission probability, or that females sought high rank (i.e. highly competitive and hence successful) males. However, the behavior of high ranked males decreased fission probability. Male herding activity was synchronous with the decrease of fission probability observed during the rut. We concluded that male herding behavior stabilized groups, thereby increasing average group size and consequently the opportunity for sexual selection.

Highlights

For reasons that remain unclear (e.g. [1]), females of polygynous species commonly move among mating groups or territories [2,3,4]
We included the following variables in the full model according to our predictions (P1, P2, P3): the social rank of the dominant male (Male; P1, P2) and the proportion of time it spent in mating-related activities (DomAct; P1); the number of satellite males in the group (NbSat; P3), and the proportion of time they spent in mating-related activities (SatAct; P3); and the percentage of time females spent feeding (FemEat; P3)
The three interactions formed with the variable Male (Male:period of the rut (Period); Male:DomAct; Male:group size (GpSize)) had high Akaike Information Criteria (AIC) weights ($0.64, Table 2), while the other interactions had AIC weights#0.46 (Table 2)

Summary

Introduction

For reasons that remain unclear (e.g. [1]), females of polygynous species commonly move among mating groups or territories [2,3,4]. Understanding factors influencing female movement is important to identify which mating behaviors drive sexual selection [11] Males may increase their mating opportunities by stabilizing their harems [7,11], whereas females may gain indirect benefits by leaving harems to sample mates [3,4,12]. We predict that (P3) the fission probability should decrease with increasing number of satellite males, and with the level of their involvement in mating-related activities It should correlate positively with the time female spend feeding, considered to be the time when they are undisturbed, as a decrease in time feeding may result from harassment (Table 1)

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