Grouping patterns show subtle social structure in a species with strong fission-fusion dynamics — ASN Events

Grouping patterns show subtle social structure in a species with strong fission-fusion dynamics (#383)

Wendy J. King 1 2 , Graeme Coulson 3 , Marco Festa-Bianchet 4 , Anne W. Goldizen 1
  1. School of Biological Sciences, University of Queensland, St. Lucia, QLD, Australia
  2. Biology Department, Bishop's University, Sherbrooke, Quebec, Canada
  3. School of BioSciences, University of Melbourne, Parkville, VIC, Australia
  4. Département de biologie, Université de Sherbrooke, Sherbrooke, Quebec, Canada

Eastern grey kangaroos Macropus giganteus are gregarious, with females mostly philopatric and most males dispersing.  Females are thus assumed to form kin clusters but details of associations among different sex-age classes in this species are largely unknown.  We observed 153 marked kangaroos at Wilsons Promontory National Park, Australia.  We examined relationships within and between six different sex-age classes using half-weight indices and lagged association rates.  We found subtle social structure.  Mean half-weight indices were similar within compared to between different sex-age combinations.  For adult females, there was a weakly positive relationship between pairwise relatedness and dyadic half-weight indices but this effect disappeared after controlling for geographic distance or spatial overlap.  Lagged association rates decreased exponentially only for adult males with adult females accompanied by young-at-foot in the breeding season.  Most other lagged association rates decreased slightly in a linear fashion and few were constant.  Although females without young-at-foot appeared to be more social than females with young-at foot, all associations among individuals were weak.  Contrary to expectations, the social structure of kangaroos was not based on female relatedness at high density under strong fission-fusion dynamics.