The role of territoriality in the mating system of the springbok Antidorcas marsupialis (Zimmerman 1780)

Abstract

The causes and consequences of territoriality were examined in the springbok Antidorcas marsupia/is. Males retained territories for extended periods, which precluded them from responding to fluctuating ecological conditions as effectively as non-territorial males or females; their home ranges were smaller, they fed less effectively than non-territorial males in the dry season, and their density on the dry riverbeds remained independent of ecological conditions including vegetation biomass, rainfall and the distance from the nearest waterhole. The social organisation of springbok exposed territorial males to the highest predation risk, whilst males in general risked a higher predation threat than females. This was reflected in both the observed predation and adult survivorship. Cheetahs were the main predator, taking twice as many adult males than females. The association of the two sexes within herds was modified by the agonistic behaviour of territorial males, which was lowest during the rut and highest at the end of the dry season. Territories were maintained through the year, despite the restricted breeding periods. Territory take-up and loss were related to both prevailing environmental conditions and rutting periods. Most territories were established and abandoned passively. Males which had abandoned a territory generally ·returned to their former territories. Sometimes males would shift territories in a year, but only if they increased the number of ewes on their territory by doing so. Such long term territory holding probably increases males' chances of retaining their territories over rutting periods, subsequently improving their reproductive success. Males held resource-based territories on the dry riverbeds and pans, where female numbers were highest. Only territorial males mated with females, though multiple mating’s by one or more males were common. Ruts were initiated by males and could potentially occur at any time of the year. A number of factors were involved in triggering rutting, though not all ruts led to successful mating’s, possibly because females were unable to respond. Ruts acted to co-ordinate mating and subsequently lambing periods, the benefits probably being enhanced male mating success at the time of the rut and an increase in offspring survival associated with the timing and synchrony of births.