Population studies of elephant (loxodonta africana) in Tsavo Ecosystem, Kenya: 1975-1980

Abstract

The population dynamics and mortality patterns of the elephant in Tsavo ecosystem between 1975 and 1980 ,.-~restudied following the recent drastic decline in their numbers. The population estimate of the live elephant population wa s determined using the systematic aerial sample count method. Based on tltO aerial counts, it was estimated that by 1980 there were about 12,000 elephants in Tsavo ecosystem. l'lost of these elephaLts were observed in the areas south of Galana riYer in Tsavo East and along and north of l'sav( river and around Lake Jipe in Tsavo "lest. There was a marked deficiency of elephant numbers in nor-t.Ler-n Tsavo East. The age structure of a sample of the live elephant population was determined using the photogra~etric technique. The results show that the present pOPlllation consists mainly of sub-adult animals \\'hose age ranges between 1 and 15 years. The popUlation has a marked deficiency in adult animals especially in localities where poaching was very rampant. The occurr~nce of large numbers of sub-adult animals in the preseat elephant popUlation seem to indicate that the potential for increase in reproduct:ion is 10'''' since the majority of the animals have not yet reached the reproductive stage. The age structure of the elephants that died between 1975 and 1980 was determined fDDm collected elephant jaws.. The age str'ucture information indicate that the juveni Le and sub-adult animals of age ranges betiwe en 0 and 10 years were most susceptible to mortalitye In adult animals~ mortality seem to have been highest in those arri.ma La with age ranges between 25 and 40 and between 45 and 50 yearso Information on the condition of the eLepha nt; car-caeae.s exam.i ried in _the field i .c. whether their crania were cut or not coupled with information from rainfall data analysis for Tsavo East for the years 1969 to 1979 indicate that the recent drastic decJ.ine in elephant numbers was caused mainly by poaching (60%) preceded by drought. Hortality due to poaching was uniformly spread over Tsavo East and Tsavo \\7est,but that due to drought was experienced mainly in Tsavo East. Using the information on the current population status, it is predicted that the Tsavo elephant number-s are not likely to increase substantially above their present numbers in the near futuro (ten or more years) due to the population'!.s low reproductive potent.ial. The probability of furt!-lCI'decline in the present population numbers seem higher than that of increasing. Two main factors that are likely to promote further decline in numbers are poaching and the continuing loss of the ranges utilized by the elephants to Iive stiock ranching and human settlement. TIle loss of the elephant ranges to huraan activities may adversely affect t.he population dynamics and ecology of the elephant. It may further promote poaching due to increase in conflict and contact between the people and the elephant. The future management problems envisaged for the Tsavo elephant will therefore centre mainly on the land-use policy and the control of poaching. It is suggested thc,t multiple-land use systems should be introduced in the areas adjoining the Park in which l..rildlifeconservation and commercial ranching should playa prominent role. To minimize the poaching of the elephant, the present anti-poaching surveillance around and wiithin the Park should continue and be strengethened" Finally it is recommended that the distribution patterns of elephants (and other game), as well as human activities around the Tsavo National Park should continue to be monitored at regular .i nt.er-va Ls on a long-term basis. "-