Association patterns and kinship in female reindeer ( Rangifer tarandus) during rut.

Non-random association of females has been reported in many social species, with kinship being the main mechanism in shaping these associations. Understanding the patterns of association during rut is particularly important in polygynous animals, as this may have implications for inbreeding vulnerability and genetic structuring of populations. However, these patterns are highly dynamic and may be influenced by the population sex ratio and male age structure. We examined females' association in reindeer ( Rangifer tarandus), a highly polygynous ungulate, to determine whether genetically related females associate more often than non-kin during rut and whether this association was influenced by the aforementioned factors. During three rutting seasons the male age structure and the sex ratio of the herd was manipulated: two extremely female biased sex ratios, one with only adult males and one with only young males, whereas the third being closer to a more even sex ratio and male age structure. We found that genetic relatedness influenced female association in the mixed male age group, but not in the adult and young male age groups. Highly related females (relatedness ∼0.5) associated more closely than unrelated females. Further, period of the rut as well as male age structure and sex ratio had a significant effect on female association. Our study suggests that the female reindeer association during rut is not only influenced by preference for kin but also by male-male competition and male age as well. [ABSTRACT FROM AUTHOR]