Biology Reference
In-Depth Information
that browse and wildebeest that graze, the units are different. Hence for kudu it is Browser
Unit (BU) and a 180kg browser will need daily 4.5kg dry mass (DM) total of grass and leaf
material per hectare p.d. and a kudu 3.5kg DM per browser unit. In addition, the general
consensus was that animal's needed water within about 4 km of grazing areas and that every
1000 or so hectares needed a water hole. Hence initially bore holes were sunk and later dams
built in the Kruger Park. In areas like this near Satara that were not highly populated they
attracted plains animals. After the nearby dam was built, then came the lions, buffalo,
elephants and rhinos.
Buffalo Herd at Water Hole
Research by Loarie and Van Aarde's group (Biological Conservation 2009) has shown that
there are two important human interventions that have strong influences on elephant
populations, namely provision of water and fences. They radio collared 73 elephants with
GPS units and tracked their movement in seven Southern African countries (Etosha, Khaudom,
Okavango, Kafue, Zambezi, Luangwa, Kasunga, Vwaza, Nyika, Limpopo, Tembe areas) over a
period of 6 years. Elephants averaged 6km per day of walking in dry areas and 3 km per day in
wet landscapes. During dry seasons they tended to move less and stayed in their home areas.
Water availability drove their movements. Their movements are also crepuscular but more
active at night than midday. Changes in direction tend to occur at midnight when they turn
around to head back to water. The provision of water by man allows for more extensive
ranging in the dry season allowing them to overexploit areas they would otherwise not utilize
in the dry season but only use in the wet season. Fences cause elephants to “bunch up” at
fences as they come across them during the wet season as they search for new habitats to feed
on. The implications are that permanent human provided water sources allow elephants to
become more like wet savannah elephants and stay in one habitat and overuse the habitat with
vegetation destruction that would otherwise not be used during the dry seasons. Clearly,
permanent river systems and the Okavango swamps allow also for overutilization of vegetation
during the dry season in the surrounding areas. Under natural circumstances there would be
more seasonality and there would be less effect on vegetation and other animals.
Many years ago the Satara area had large plains of tall grasses and, except along the
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