The commuting system of Serengeti spotted hyaenas: how a predator copes with migratory prey. I. Social organization

Abstract

Abstract. The social organization and space use of spotted hyaenas, Crocuta crocuta Erxleben, in the Serengeti, Tanzania is described. In contrast to Kruuk (1972, The Spotted Hyena. Chicago: University of Chicago Press), spotted hyaenas in the Serengeti live in large stable groups (clans); median clan size for seven clans was 47 adults and subadults. Clans defended permanent territories that contained the communal den. The size of one well-known territory was 55·5 km 2. Territories contained low densities of resident herbivores (mean 3·3 animals/km 2) throughout the year, but experienced very high densities (mean 219 animals/km 2) of migratory herds, principally wildebeest, Connochaetes taurinus , zebra, Equus burchelli, and Thomson's gazelle, Gazella thomsoni, for only 26% of the year. The most important prey killed inside territories were migratory species. When the migratory herds were away from a clan's territory, clan members regularly left the territory to forage on nearby migratory herds ('commuting trips'). Clan sizes were maintained above the carrying capacity of the territory, estimated from populations of resident herbivores, by year-round exploitation of migratory herbivores. This suggests that, in contrast to many other carnivores, group sizes of Serengeti hyaenas are not limited by resources on the territory and feeding ranges are decoupled from territoriality.