L’«Opération Éléphants » au Rwanda — 2e partie. Acclimatation et régime des jeunes éléphants introduits dans le parc national de l’Akagera

Abstract

In 1975, twenty-six calves and immature elephants were captured in southern Rwanda and relocated in the Akagera National Park in northeastern Rwanda, where no elephants had been sighted for some decades. This paper is a preliminary report on the adaptation of these elephants to their new environment. The young elephants belonged to different family units but, in their new habitat, they formed stable social herds. During the study period, they remained on a 1200 ha home range on a peninsula in the large swampy depression of the Akagera River. Food habits were studied by direct and indirect observations. Eighty plant species were found to be eaten, and 3071 recorded observations were analysed. There were marked seasonal changes in the diet. The elephants did not seem to be affected by undernutrition in the dry seasons. Creepers, trees, shrubs, and swampy herbs and grasses were abundant and dominant in the diet. Grazing increased at the beginning of wet seasons when food plants were richest in nutritive value. Most of the grasses were avoided at the end of the rains and in dry seasons. The impact of browsing and grazing was most marked in the riverine vegetation utilized intensively all the year round, where some plants, such as Sesbania sesban, were heavily damaged. In the savanna woodland, the vegetation was only lightly damaged. The impact of browsing on the vegetation, was usually compensated by plant growth, but browsing nevertheless affected the stature of some plants. Ecological succession in the Akagera Park seems to evolve towards a natural reforestation and the clearings made by a small population of elephants might be beneficial for most grazing animals. The possibilities of local competition between elephant and buffalo for some swampy and riverine pastures during drought periods are evoked.