Has the Luangwa (Zambia) hippopotamus (<i>Hippopotamus amphibius</i>) population stabilized after reaching its asymptote? What are the management challenges?

Abstract

The population size of hippo (HippopotamusamphibiusLinnaeus 1758)in Luangwa valley, Zambia was earlier assessed for the period 1976 - 2008 and repeated 2009-2012 and found to have reached and maintained carrying capacityKof 6000 individuals over a165 kmriver stretch. This study covered the period 2009 -2012 and used river bank count method as in previous studies. The method involved counting individuals and taking GPS locations of hippo schools. During the period 2009-2012the population had maintained irregular cycles oscillating above and below K of 6000 and was still within carrying capacity band of 2000 individuals. The highest population size was still 6832 hippos (rounded off to 7000) and density of 42/km reached in 1984, and the lowest was 4765 hippos (rounded off to 5000) and density of 29/km recorded in 1978. Between 1976-2008, and 2009-2012 the population still oscillated between 5000 - 7000 individuals, which is symptomatic of a population that had reached its asymptote. Plot of population size for the period 1976-2012 assumed a population model which was a hybrid between less accurate regulation and stable limit cycle. The slowdown in population growth atKand oscillationswere attributed to environmental resistance.More studies are required to identify the impact of climate change on the population size and density fluctuations to determine whetherKwill rise or drop.