Relationships among parental inbreeding, parental behaviour and offspring viability in oldfield mice.

Studies of inbreeding depression have traditionally suffered from two weaknesses. First, they usually confound offspring deficiencies with parental ones; second, they neglect the possible role of behaviour in inbreeding depression. In the present study, I examined the relationship among parental inbreeding, offspring viability and parental behaviour in two subspecies of the monogamous oldfield mouse, Peromyscus polionotus. Parental inbreeding was separated from any offspring inbreeding effects through both experimental design and analysis. Dams performed more parental behaviour than did sires, and maternal behaviour had a stronger effect on offspring survival than did paternal behaviour. Maternal behaviour was more buffered to the effects of inbreeding than was paternal behaviour; that is, parental behaviour of inbred females was not compromised. In contrast, inbred males showed substantial deficits in parental behaviour, but this did not put their offspring at risk. Although inbred females had lower reproductive success than outbred females, this effect was not manifest in terms of lower offspring viability. Therefore, inbreeding depression manifests itself through deficits on traits of adult females other than maternal care. A possible physiological basis for these findings is hypothesized.Copyright 1998 The Association for the Study of Animal Behaviour.