Giraffe foraging ecology in the Tarangire Manyara ecosystem, Tanzania

Abstract

Management of rangelands requires knowledge of forage species that are preferred or avoided by wildlife and livestock. The recent and rapid transformation of habitat by humans has led to increased concerns about the proper management of rangelands. In East African savanna ecosystems, the expansion of woody vegetation into previously open grasslands has led some rangeland managers to advocate for the active removal of native bushes to maintain grazing lawns in African savanna ecosystems. However, little is known about how browsing herbivores might benefit from the ingrowth of woody vegetation. Diet selection by the Masai giraffe (Giraffa camelopardalis tippelskirchi) was quantified in the Tarangire Manyara Ecosystem of Tanzania. Instantaneous scan sampling was used to quantify foraged woody plant species and compare those data with proportions of available woody plant species at two different spatial scales during a wet and dry season and between areas of different protection statuses. Study results showed that giraffes demonstrated strong selection towards some woody plant species while avoiding others, both at the local and the landscape scale. Giraffes preferentially used more forage species in less protected areas (8 forage species) than in a fully protected area (only 1 species). At both spatial scales, giraffes significantly preferred the shrub Dichrostachys cinerea, a species that livestock managers have classified as encroacher species needing removal. This preference was visible in the wet and dry seasons. The results of this study suggest that browsing wildlife species such as giraffes may be adversely affected by the removal of D. cinerea from rangelands and that managing for grazing livestock only could negatively impact browsing wildlife on mixed-use lands.