Le but de cet article est d'etablir les rendements bioenergetiques et le bilan nutritionnel des jeunes 61£phants.Deux Elephanteaux apprivois£s äg£s de 27 et 31 mois, ont ete maintenus en enclos et nourris des meines plantes que eel les qu'ils choisissent en liberte. La quantity de nourriture qu'ils ont mangle a et^ mesuree avec precision ainsi que les reject a provenant de cette nourriture.Les rlsultats donnent des taux de digestibility des aliments naturels (assimilation/consommation) de 38,8 ± 4,4 % et de 45,6 ± 2,8 % soit une moyenne de 42,1 %. Les rapports consqmmation/dofecation sont de 1,67 ± 0,11% et de 1,84 ± 0,10, soit une moyenne de 1,73.Ces rapports presentent un intdrSt particulier car ils permettent de connaltre la quantite de nourriture ingoroe sur le terrain et la part qui est assimilee grace a la mesure de la quantite et du taux de matieres f Scales gliminies par jour. Sur la base des rosultats obtenus, nous avons elabli un bilan energotique valable pour les elophanteaux en pleine poriode de croissance.(*) Avec la collaboration technique de Jean-Marc FROMENT.

Population ecology of wild ungulates has been studied during two consecutive years (September 1968 -August 1970) in the Akagera National Park, Rwanda. Counts have been made four times a month on six line-transects using a technique similar to that of Lamprey (1963-64). Each of the 13 more common species has it own ecological preferences, and no inter-specific competition occurs (Table I). Average densities and standing crop biomasses are given for each of the major habitats of the area (Tables II, III, IV). The densities of sedentary species are remarkably stable from year to year. Average standing crop biomasses (fresh weight) range from 2705 Kg/Km2 in the Mutara grasslands to 28.286 Kg/Km2 in the tree savanas of the plains. Seasonal fluctuations are due to the seasonal breeding of some species and seasonal migrations of others. Data are given on the sex-ratio and age-ratio of the major species. Their social structure is described. Habitat is shown to influence social structure in the Topi and the Impala. Both species have different patterns of population dispersion and social grouping in different vegetation types. Among impalas, and apparently also among topis, the percentage of young of the year and juvenile individuals is smaller in areas of high population density.