The ecology of the Kafue lechwe population of Zambia before the operation of hydro‐electric dams on the Kafue River

Abstract

SummaryAerial surveys from 1970 onwards suggest a stable Kafue lechwe population of 94 000±9% on the Kafue Flats. The present distribution shows a contraction in dry and wet season range in comparison with 1953/54.Sex ratios of populations on both the North and South banks of the Kafue river do not differ significantly from unity. North bank males have a higher survival rate than South bank males. Survival curves for males and females on the South bank show the same pattern. For both the 1971 and 1972 breeding seasons 73% of South bank females older than 1½ years are expected to have bred successfully. The peaks of conceptions for both seasons are from mid‐December to mid‐March, suggesting a main lambing period from mid‐July until mid‐October. Present sex ratio, age structure, reproductive status and the reproductive cycle have been compared with 1961/62 data.Variation in physical condition, based on monthly measurements of the kidney fat percentage, dressing‐out percentage and live weight, although influenced by the physiological demands of rut and pregnancy, is correlated with the availability of flood‐plain grazing. The lowest values of condition parameters are found during the period of maximum flood, after the end of the rains (April/May), until the receding flood makes flood‐plain grazing available, usually in early June. A high level of tuberculosis, lungworm infection and many other pathogens amongst the South bank population are reported. Animals from the North bank are thought to be in better physical condition.The Kafue Gorge dam, completed in 1971, and the Iteshi‐teshi dam, at present under construction, will prolong the high flood period in wet years and prevent most flooding in dry years, both of these effects will reduce the carrying capacity of the flood plain for lechwe and a large reduction of the size of the population is expected to result from the operation of the dams.