A
Grazer Populations by Year (Balule NR)
0.025
Blue Wildebeest Plains Zebra Waterbuck
# Individuals per hectare
0.02
Warthog 0.015
Buffalo Hippopotamus
0.01
White Rhinoceros 0.005
Ostrich Bushpig
0 1999 2001 2003 2005 2006 2007 2008 2009 2011 2012
B
Average Grazer Population (Balule NR) Log10 of population
2.5 2 y = -0.047x + 2.379 R² = 0.6109
1.5 1 0.5 0 1999
2001
2003
2005
2006
2007
2008
2010
2011
2012
Figure 1. A) Population density changes in important grazer species in the Balule Nature Reserve. Several species (waterbuck, blue wildebeest, plains zebra) have decreased, while other species (buffalo, warthog, hippopotamus) have increased. B) Average grazer population in the Balule Nature Reserve over the past 13 years. Grazers have overall decreased slightly, but have increased between 2011 and 2012. Log10 of population was used in both cases to avoid biases in the data due to particularly large or small populations.
Observer bias can account for the fluctuations between 2011 and 2012 as well as the emigration of species across borders. The trend however is still downward for the whole of Balule but long term monitoring is required to show if this is of significants.