Effect of polygyny on female reproductive success in the mandarin vole, Microtus mandarinus (Rodentia, Arvicolinae)

Abstract

Indices of reproductive success were compared in monogamous and polygynous groups (MGs and PGs) of female mandarin voles kept under different laboratory conditions: in small cages, with frequent handling disturbance (30 MGs and 15 PGs), and in large glass tunnel systems, without disturbance (20 MGs and 16 PGs). MGs consisted of unrelated male-female pairs, and PGs consisted of two female sibs and an unrelated male each. No reproductive skew was observed within PGs; moreover, there was a positive correlation between the sibling females in the presence/absence of offspring, its total size, and the number of litters produced over 90 days. Regardless of keeping conditions, the proportion of parous females recorded over 45 days and the number of successfully reared offspring per female were greater in MGs than in PGs. Among groups kept in cages, reproductive success in PGs was lower because of a delay in breeding, reduced size of the first litter, and increased pup mortality during the first days of life. Observations on voles in tunnel systems were performed to quantify aggressive interactions and reveal the causes of pup mortality. In general, the level of aggression in both types of groups was low, but the frequency of female-female conflicts in PGs drastically increased during several days before and after the birth of the litter. Nevertheless, the sibling females in PGs used the common breeding nest and regularly fed reach other’s offspring. The causes of high pup mortality in PGs and probable advantages of communal breeding in mandarin voles are discussed.