Topi - Social Structure and Reproduction

Social Structure and Reproduction

The topi has what is possibly the most diverse social organization of the antelopes. Topi herds can take the form of "perennially sedentary-dispersion", "perennially mobile-aggregated" or something in between. This depends on the habitat and ecology of the areas they are in. In addition, the reproductive organization ranges between the traditional territorial system or resource defense polygyny herds to gatherings that contain short-lasting territories to lek systems. In patches of grassland surrounded by woodlands, topi live in the sedentary-dispersion mode. Males establish territories that attract herds of females with their offspring. Depending on the size of the patches, territories can be as large as 4 km2 and sometimes border each other. The fidelity of a female to a territory can last three years in the Serengeti. The females in these territories function as part of the resident male’s harem. These herds tend to be closed (expect when new females are accepted) and both the male and his females defend the territory. When the resident male is absent, the dominant female may assume his behaviors, defending against outside topis of either sex using the rocking canter and performing the high-stepping display. In more densely populated areas, like those of Queen Elizabeth National Park in Uganda, topis move across the plain and set up territories during resting periods.

In areas such as the Akagera National Park in Rwanda and Masai Mara National Reserve in Kenya, topi males establish leks which are territories that are clustered together. These territories have little value outside of the males in them. The most dominant males occupy the center of the lek cluster and the less dominant occupy the periphery. Males mark their territories with dung piles and stand on them in an erect posture ready to fight any other male that tries to invade. Estrous females enter the leks both alone and in groups and mate with the males in the center of the lek cluster. Males further from the center may increase their reproductive success if they are near water. Females will compete with each other for the dominant males as females come into estrous for only one day of the year. Females prefer to mate with dominant males that they have mated with before, however males try to mate with as many new females as possible. As such favored males prefer to balance mating investment equally between females. Females, however, will aggressively disrupt copulations that their favored males have with other females. Subordinate females have their copulations interrupted more often than dominant females. Males will eventually counter-attack these females, refusing to mate with them any more.

The vast majority of births occur between October and December with half of them occurring in October. The parenting of the topi has characteristics of both the "hider" system (found in the blesbok) and the "follower" system (found in the blue wildebeest). Calves can follow their mothers immediately after birth and "may not 'lie out'". On the other hand, females separate themselves from the herd to calve and calves commonly seek hiding places during the night. A young stays with its mother for a year or until a new calf is born. Both yearling males and females can be found in bachelor herds.