Habitat use and group size of African wild ungulates in a Namibian game ranch

Aim of this research was to gather information on group size and habitat use by the different ungulate species and spatial overlap among species. Data were collected in the dry season in a fenced area (5021 hectares) during 44 game drives along five different routes; for each sighting, we recorded species, day, time, location (on a map divided into square grid units of 500 m sides), number of animals and habitat type. Duiker (Sylvicapra grimmia) was the more solitary species, followed by steenbok (Raphicerus campestris) and warthog (Phacochoerus africanus), while hartebeest (Alcelaphus buselaphus), blue wildebeest (Connochaetes taurinus), eland (Taurotragus oryx) and mountain zebra (Equus zebra hartmannae) usually formed large groups. This is in agreement with the normal social behaviour of these species. Nevertheless, the high percentage of solitary oryx (Oryx gazella), greater kudu (Tragelaphus strepsiceros), springbok (Antidorcas marsupialis) and impala (Aepyceros melampus) is unusual. The frequent presence of isolated individuals in gregarious species may indicate a dispersion of the animals in the territory due to reduced food availability. Some of the species showed their typical habitat use; however, some species also used less suitable habitats. A low degree of spatial overlap was observed between most of the species. In spite of this, in some cases a considerable overlap occurred. For example, kudu and springbok, which had a wide spatial distribution, showed a high degree of spatial overlap with other species (e.g., all of the grid units used by zebra were used in common with kudu, and 88% of the grid units used by blesbok was in common with springbok). Data indicate that animals are overabundant in this fenced area and they are suffering from the dry season.