Does shore length influence population size and density distribution of hippopotamus?

Abstract

Population surveys of common hippopotamus (Hippopotamus amphibius) in Zambia were carried out between 2005 and 2008 to estimate population size and density distribution patterns against shore length. River bank foot counts were used in the Luangwa River system while boat/canoe counts were used to collect population data from lakes, dams and rivers. Population estimate was 40,060 hippopotami distributed over shore length of 11, 892 km. Luangwa, Zambezi and Kafue Rivers had shore length of 4,150 km which was only 35% of total shore length. The three rivers with only 35% of shore length had 35,000 individuals which was 87.36% of total population estimate, distributed as follows; Luangwa 25,000 (62% of total), Zambezi 6,500 (16% of total) and Kafue 4,000 (10% of total). Chisquare test showed a significant difference in population estimates in Luangwa, Zambezi and Kafue ( 2 , P < 0.05) being highest in the Luangwa (62%), Zambezi (16%) and Kafue (10%) respectively. It was found that shore length did not determine population density distribution. The Luangwa River which was not the longest had the largest number of hippopotamus supporting 62% of the national population estimate. More research is required to investigate other physical and anthropogenic factors determining hippopotamus population density distribution along shore length of water bodies.