Insights from the pedigree on the social structure of free-roaming Konik horses (Equus caballus) in a Dutch reserve

Social interactions in group-living animals are complex and involve diverse aspects of the groups and the  individuals that form them. Only in few studies the researchers know the genetic relations among individuals in  the group, yet such knowledge may shed light on the social relationship within the group. We observed behavior  and movement of 27 Konik horses (Equus caballus) that were introduced for habitat management to the Blauwe  Kamer Reserve, Netherlands, and are mostly not managed by man. Genetic samples were collected from each  horse, the parents of horses that were born on the reserve were determined, and the pedigree was reconstructed.  We recorded observations simultaneously on two digital video cameras: one recording the entire groups and the  positions of individuals and the other zoomed in on each horse to assist in individual recognition. The social  network was analyzed based on positive affiliation and proximity, after aggressive interactions were removed.  Not counting foals, the horses clustered in two harem groups with 11 individuals (two of which were adult  stallions) and six individuals (one of which was a stallion), respectively. Two bachelor males often moved in the  harems‟ vicinity and three additional young bachelor males roamed elsewhere in the reserve. Degree (number of  connections of an individual) and betweenness centrality are measures of centrality and they were not associated  with age or rank. However, these measures emphasized connections that were formed during the study period and  that eventually led to the move and acceptance of three individuals into the smaller harem. The comparison of  harem composition to the pedigree revealed that the large group, which includes the oldest individuals, supplied  young females that eventually formed the smaller harem. The small harem did not contribute any individual to the  larger group, perhaps because the juveniles that were born and matured in it so far were all males. The genetic  analysis revealed that one of the foals whose mother belong to the larger group was not fathered by any of the  stallions of the harem, in spite of the efforts of the stallions to keep other males away from the harem‟s females.  The comparison between the social interactions and the pedigree revealed that at least two males attempted to  mate with their own daughters. The current study contributes to the understanding of processes that groups of  horses undergo when enclosed in a limited area reserve with no options for emigration / immigration. The only  human intervention in the Blauwe Kamer Reserve is the occasional transfer of individuals into or out of the  reserve. Our results can suggest slight modifications in the management of the horses to reduce the risk of  inbreeding.