Effects of social organization, age and aggressive behaviour on allosuckling in wild fallow deer.

I investigated the occurrence, frequency and distribution of allosuckling in a wild population of fallow deer, Dama dama, throughout the lactation period during 1992 in southern Sweden. A total of 292 suckling bouts were observed in four groups; in 43% of these, fawns were seen sucking from a female that was not the mother. Allosuckling occurred in a higher percentage of suckling bouts as the lactation period progressed and all 16 fawns participated to various degrees. Of the 16 females, 13 suckled nonoffspring fawns but their behaviour towards these fawns varied greatly. Allosuckling was positively correlated with the age of the females and negatively correlated with the rate of their aggressive behaviour. Since allosuckling was not performed between groups but was common between related members in a stable social unit and was expressed reciprocally between the oldest individuals in the group, allosuckling could be a result of kin selection and/or reciprocal altruism. Copyright 1998 The Association for the Study of Animal Behaviour.