SW162 Calculating the carrying capacity of the Royal Jozini Reserve for elephant populations,
South Africa
The rate of elephant population growth on game reserves is of high importance particularly because
of the intense impact on vegetation. As densities change, elephants are prone to fluctuations that
are extrinsic, resource driven and intrinsic, demographics. As an extrinsic driver, surface water
availability and preferred food are key drivers of elephant populations and range use.
Between 1997 and 2001 elephant herds and individuals were introduced onto Pongola Game
Reserve, Kwa-Zulu Natal. Prior to introduction plans for land expansion for the elephants had been
drawn up. The area around Lake Jozini was to be transformed into a Transfrontier Conservation Area
with Swaziland. The fences were to be dropped from the southernmost tip of the lake which falls on
South African government land, north through the Pongola Game Reserve, Pongola Nature Reserve
and into Royal Jozini Big 6 Reserve (RJB6) in Swaziland. To date this has not yet taken place.
In anticipation of range expansion which would accommodate population increases, there was a
delay in population control. The population growth rate of the introduced elephants was high before
being controlled through management intervention. The introduced population of 30 individuals has
since grown into ±85 elephants which make up the two family herds A and B that fused, an Orphan
herd and sub-adult/adult bulls. Consequently there has been pressure for the reduction of the
elephant population in order to leave sufficient forage for other browsing species.
As a result of the severe drought experienced in 2016, the water of Lake Jozini has reduced to about
a third of its capacity. This left space between the water edge and the fence line to allow ± 58
elephants to move from Pongola into the Royal Jozini Big 6 Estate. This estate is a 14,000 ha game
reserve in the southern region of Swaziland. Prior to this movement there were no elephants on the
reserve however buffalo, rhino and leopard already occur. Other animals on the RBJ6 include
waterbuck, blue wildebeest, kudu, zebra and hippo.
To measure the impacts of the elephants on the vegetation in RJB6 we will conduct habitat
assessments. On the RJB6 we will identify 30 new sites that are 20x20 metre plots. Within those
plots, we will collect the following data for every woody plant over 1 metre: species, basal stem
diameter, height, height and width of the widest point of the canopy and an assessment of impact
from elephant, fire or other source. Elephant impact is recorded using the Walker seven-point scale
(Walker 1976), allowing for quantitative assessment.
Additionally, we need to accurately assess the amount of leaf material available for browsing game
species between 1 and 2m off the ground. This will be done during the winter period when the
volume and calorific value of forage available will be at its’ tightest point in the year. A 20m x 20m
square will be positioned randomly adjacent to each of the habitat assessment plots. The volunteers
on the project will then remove all the leaves and petioles from within the first 2m height in these
20m x 20m quadrats. Where the thickness of the bushes is considered so great that the inner leaves
could not be browsed by the various species these will be left. The leaves collected will be separated
into two bags (i.e. those below 1m and those collected from 1 – 2m). The total weight of leaves and
petioles in each of the categories will then be weighed and dried so that the calorific value can be
measured at a later date. The daily calorific value and weight of forage required to maintain
condition and the height of browsing is known for each of the browsing species so these data can
then be used in combination with the forage weight and calorific value available in the winter
months to estimate the carrying capacity of browsers.
Recommended reading
Please note: the following is intended as a starting point only, and students are expected to read
more widely on their chosen topic to inform their project background and planned analysis.
Birkett and Stevens-Wood (2005) Effect of low rainfall and browsing by large herbivores on an
enclosed savannah habitat in Kenya. Afr. J. Ecol. 43: 123–130
Birkett (2002) The impact of giraffe, rhino and elephant on the habitat of a black rhino sanctuary in
Kenya. Afr. J. Ecol. 40: 276-282
Edkins, M., Kruger, L., Harris, K. and Midgeley, J. (2007) Baobabs and elephants in Kruger National
Park: nowhere to hide. Afr. J. Ecol. 46: 119–125
Grant, C. C., Bengis, R., Balfour, D. And Peel, M. (2007) Controlling the distribution of elephant. In:
Assessment of South African Elephant Management, 2007.
Kerley, G., Landman, M., Kruger, L. and Owen-Smith, N. (2007) Effects of elephant on ecosystems
and biodiversity. In: Assessment of South African Elephant Management, 2007.
Levick, S. and Rogers, K. (2008) Patch and species specific responses of savanna woody vegetation to
browser exclusion. Biological Conservation 141: 489-498
Lombard, A., Johnson, C., Cowling, R. and Pressey, R. (2001) Protecting plants from elephants:
botanical reserve scenarios within the Addo Elephant National Park, South Africa. Biological
Conservation 102: 191–203
Mapaure, I. and Moe, S. (2009) Changes in the structure and composition of miombo woodlands
mediated by elephants (Loxodonta africana) and fire over a 26-year period in north-western
Zimbabwe. Afr. J. Ecol. 47: 175–183
Ribeiro, N., Shugart, H. and Washington-Allen, R. (2008) The effects of fire and elephants on species
composition and structure of the Niassa Reserve, northern Mozambique. Forest Ecology and
Management 255: 1626–1636
Shannon, G., Page, B., Duffy, K. and Slotow, R. (2006a) The role of foraging behaviour in the sexual
segregation of the African elephant. Oecologica 150: 344–354
Shannon, G., Page, B., Slotow, R., and Duffy, K. (2006b) African elephant home range and habitat
selection in Pongola Game Reserve, South Africa. African Zoology 41(1): 37–44
Shannon, G., Matthews, W., Page, B., Parker, G. and Smith, R. (2009) The affects of artificial water
availability on large herbivore ranging patterns in savanna habitats: a new approach based on
modelling elephant path distributions. Diversity and Distributions 15: 776–783
Smit, I., Grant, C. And Whyte, I. (2007) Landscape-scale sexual segregation in the dry season
distribution and resource utilization of elephants in Kruger National Park, South Africa. Diversity and
Distributions 13: 225–236
van Aarde, R., Ferreira, S., Jackson, T. and Page, B. (2007) Elephant population biology and ecology.
In: Assessment of South African Elephant Management, 2007.
van Aarde, R. and Jackson, T. (2007) Megaparks for metapopulations: Addressing the causes of
locally high elephant numbers in southern Africa. Biological Conservation 134: 289-297