Inter- and Intra specific Conflict between Arid-zone Kangaroos at Watering Points

Abstract

Red kangaroos Macropus rufus and euros M. robustus were observed drinking at a stock trough in northwestern New South Wales. The populations of both species were divided into five age-sex classes. Drinking and agonistic behaviour was similar across classes and species. Inter- and intraspecific conflict between these classes for a drinking position were analysed. Within species, there is a size-related hierarchy for gaining and maintaining a drinking space, favouring the larger class. Interspecifically, euros, the smaller species, dominate equivalent age classes of red kangaroos. Retaliation in aggressive encounters is more likely between adjacent rank neighbours than those more distant in the hierarchy. Drinking individuals tend to win more encounters than individuals attempting to gain a drinking place. The longer a kangaroo has been drinking the less likely it is to act aggressively to an intruder. When drinking, spacing between kangaroos is essentially random. Both species displace another individual at a similar mean distance of 0.6-0.8 m, but spacing between adult euros is wider than between adult red kangaroos. Spacing is modified by the relative positions of neighbours on either side of the trough. The results are discussed in terms of social and other factors that may have led to the euro's dominance of the red kangaroo at water.