The nasty neighbour in the striped mouse (Rhabdomys pumilio) steals paternity and elicits aggression
1 Institute of Evolutionary Biology and Environmental Studies, Department of Animal Behaviour, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland
2 School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
3 University of Muenster, Department of Behavioural Biology, Badestr. 9, 48149 Münster, Germany
Frontiers in Zoology 2010, 7:19 doi:10.1186/1742-9994-7-19Published: 23 June 2010
Territoriality functions to monopolize access to resources including mates, but is costly in terms of energy and time investment. Some species reduce these costs by being less aggressive towards their neighbours than towards unfamiliar strangers, the so called dear enemy phenomenon. However, in other species individuals are more, not less aggressive towards their neighbours. It has been hypothesised that this is due to the fact that neighbours can impose a greater threat than strangers, but this has not been tested previously.
We tested aggression in wild group-living male striped mice in a neutral test arena and demonstrate that breeders are more aggressive than non-breeding philopatrics, and that more aggression occurs during the breeding than during the non-breeding season. Male breeders were significantly more aggressive towards their neighbours than towards strangers, leading to the prediction that neighbours are the most important competitors for paternity. Using a molecular parentage analysis we show that 28% of offspring are sired by neighbouring males and only 7% by strangers.
We conclude that in male striped mice the main function of male aggression is defending paternity against their territorial neighbours.