ESTIMATION OF THE LARGE MAMMAL DENSITIES, BIOMASS AND ENERGY EXCHANGE IN THE TARANGIRE GAME RESERVE AND THE MASAI STEPPE IN TANGANYIKA

Abstract

Summary: An account is given of the transect system of game counting used in this study, including the use of a visibility profile to determine the absolute area covered. Monthly density figures derived from the transect counts over four years are given for each of the common species separately and for the large mammal population as a whole. Direct aerial counting and total counting on the ground were employed to provide checks on the transect results and the former method was also used to obtain an overall population estimate of the Tarangire Game Reserve. The application of statistical analysis to the numerical data obtained is discussed and, because of the time‐serial correlation of the monthly values, a non‐parametric method is employed to confirm the significance of as many as possible of the density fluctuations indicated. Within the Tarangire Reserve, the annual density of large mammals varied between c. 60 animals per square mile in the rains and c. 250 animals per square mile during the dry season concentration. Aerial and ground survey and counting of the dispersed animals in the Masai Steppe provided data on the extent and the routes of the dispersal of animals after they leave the Reserve in the rains, and indicate a dispersal density of 2.5 animals per square mile (as compared with 80–140 animals per square mile in the similar country of the Serengeti Plains). The lowness of this density is attributed to human activity over the last 50 years, particularly to the removal of dry season water supplies. The seasonal fluctuations in numbers in the Tarangire Reserve, due to the movement of some species, are discussed and the ungulates are classified as residents and immigrants. The residents are further divided into those which have partial dispersal in the rains and those which do not. Impala numbers fluctuate seasonally but with a phasing which is the opposite of that of the immigrant species. A further element in the population consists of passage migrants which occur irregularly in the Tarangire Reserve as they move from one part of the dispersal area to another in the rains. Estimates of the biomass and of the metabolic energy expenditure rate in the transect‐area population indicate that the total varies between 16,000 Calories per hour per square mile (16,000 lbs weight: 60 animals per square mile) in the rains, and 170,000 Calories per hour per square mile (207,000 lbs weight: 250 animals per square mile) in the dry season. The results confirm the very high carrying capacity of African Acacia savanna game range.