Influence of different social partners on the survival and growth of pups in two species of Calomys (Muridae Sigmodontinae)

Abstract

In this paper we investigated if the contact of a mother-pups unit with different partners may affect pup survival and growth in Calomys musculinus and C. laucha. Mother-pups units were housed with either a virgin female, a familiar male or a strange male, and the effect of these partners on the litter was measured from birth through weaning. In C. laucha both the presence of a strange male or a virgin female was deleterious for pup survival and growth. In C. musculinus, however, the presence of any partner, even the siring male, decreased pup survival and growth (the strange male was the most deleterious for pup growth). In both species the virgin female partner was killed in approximately half of the cases, while there was a differential response to the strange male, C. laucha females appeared less tolerant to strange males than their C. musculinus counterpart, which is consistent with the idea that C. musculinus females interact in nature with more than one male in their home range. All of the familiar males survived. This study provides evidence that C. laucha pups grow better in the presence of either the mother alone or in the partnership of the familiar male, while in C. musculinus, the presence of any partner, even the siring male, is deleterious for litter survival and growth under laboratory conditions. In the context of previous evidence, the current results are interpreted to mean that C. laucha is closer than C. musculinus to the monogamy end of a three-dimensional system for the definiton of monogamy.