TITLE:
Has the Luangwa (Zambia) hippopotamus (Hippopotamus amphibius) population stabilized after reaching its asymptote? What are the management challenges?
AUTHORS:
Chansa Chomba, Twakundine Simpamba, Vincent Nyirenda
KEYWORDS:
Hippo; Density; Population; Stability;Asymptote; Carrying Capacity; Oscillations
JOURNAL NAME:
Open Journal of Ecology,
Vol.3 No.6,
October
8,
2013
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.