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.

Behavioural risk factors in the reproduction of inbred and outbred oldfield mice

The present study investigated two rarely measured aspects of inbreeding depression: the relationship between inbreeding and behaviour, and the possibility that inbred individuals that survive infancy may still suffer from inbreeding depression by failing to breed or failing to show appropriate mating or parental behaviours. Specifically, the relationship between (1) behaviour at pairing and reproductive success, (2) inbreeding and reproductive success and (3) inbreeding and pairing behaviour, was examined in two subspecies of the oldfield mouse, Peromyscus polionotusEffects of parental and offspring inbreeding were separated through experimental design and analysis. Activity level during the first 25 days after pairing predicted future reproductive success: pairs that remained less active during the nocturnal (active) period were significantly less likely to breed than pairs that remained more active. Inbred females took significantly longer to produce their first litters and were less likely to produce litters than were outbred females, independently of whether females were related to their mates (i.e. whether their offspring would be inbred). Inactive pairs averaged fewer surviving pups than did active pairs. Inbreeding coefficient of female was a significant predictor of activity level in one of the two subspecies, suggesting that inbreeding may affect behaviour. Inbred adult females showed inbreeding depression in the form of lower conception rates and fewer surviving offspring, although the specific traits affected differed for the two subspecies. The implications for captive breeding programs, and likely causes of the subspecific differences, are discussed.