The role of the ram in the impala (Aepyceros melampus) mating system

Abstract

The role of territoriality was investigated using 25 impala rams in a site in South Africa. Field data were used to determine known rams as territorial and bachelors, as well as aspirant and indeterminate. The mean territorial tenure was 67.25 days, with a mean territory size of 21.0 ± 11.27 ha, compared to the home ranges of 34.1 ha ± 9.03 ha for territorial and 58.8 ha ± 33.35 ha for bachelor males. Territory boundaries seemed to remain constant through the season, and are smaller when bordering important features such as water holes, which appear to be neutral in terms of territoriality. Mating was observed on three separate dates between 16 May - 4 June 2001, three times by territorial males, the exception being an aspirant ram. The most important diurnal behaviour was feeding, followed by watching, walking, ruminating, resting and licking salt. It was found that bachelors browse more than territorial males, and all males browse and lick salt more in the non-rut. All rams were also more vigilant after lions were released. Only bachelors spar and allogroom, and they also orally groom themselves more than territorial males. Territorial males chase and roar more, and perform longer object aggression acts during the non-rut than bachelors. Other behaviours were rare or performed by all rams during the year.