Seasonal movements of giraffes in Niger

Abstract

The last population of giraffes in west Africa lives in Niger in an unprotected Sahelian region inhabited by farmers and herders. The spatial behaviour of each individual of the population (n = 63) was studied by direct observation during 15 mo. Two-thirds of the population were resident in the tiger bush in the rainy season and in the nearby area of Harikanassou, a sandy agricultural region, in the dry season. Rainy season and dry season home ranges were mutually exclusive and individual home ranges were overlapping when considering one season (rainy season: 84%; dry season: 67%). The mean size of the seasonal home ranges of these resident giraffes during the dry season (90.7 km²) was twice the mean size during the rainy season (46.6 km²). A third of the population moved 80 to 200 km in three directions, and two giraffes from an isolated group from Mali moved 300 km along the Niger River. Long distance movements of such length have never been reported before, and several explanations are proposed: previous distribution, social transmission, hydrographic network and food availability, poaching events. The giraffes in Niger do not avoid rural communities; indeed, they live in densely populated regions. Furthermore, their movements, synchronized with human activities in these regions, are representative of life conditions in the Sahel.