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Elephant (
Loxodonta africana
) Home Ranges in Sabi
Sand Reserve and Kruger National Park: A Five-Year
Satellite Tracking Study
Bindi Thomas, John D. Holland*, Edward O. Minot
Ecology Group, Institute of Natural Resources, Massey University, Palmerston North, New Zealand
Abstract
During a five-year GPS satellite tracking study in Sabi Sand Reserve (SSR) and Kruger National Park (KNP) we monitored the
daily movements of an elephant cow (Loxodonta africana) from September 2003 to August 2008. The study animal was
confirmed to be part of a group of seven elephants therefore her position is representative of the matriarchal group. We
found that the study animal did not use habitat randomly and confirmed strong seasonal fidelity to its summer and winter
five-year home ranges. The cow’s summer home range was in KNP in an area more than four times that of her SSR winter
home range. She exhibited clear park habitation with up to three visits per year travelling via a well-defined northern or
southern corridor. There was a positive correlation between the daily distance the elephant walked and minimum daily
temperature and the elephant was significantly closer to rivers and artificial waterholes than would be expected if it were
moving randomly in KNP and SSR. Transect lines established through the home ranges were surveyed to further understand
the fine scale of the landscape and vegetation representative of the home ranges.
Citation: Thomas B, Holland JD, Minot EO (2008) Elephant (Loxodonta africana) Home Ranges in Sabi Sand Reserve and Kruger National Park: A Five-Year Satellite
Tracking Study. PLoS ONE 3(12): e3902. doi:10.1371/journal.pone.0003902
Editor: Jerome Chave, Centre National de la Recherche Scientifique, France
Received August 4, 2008; Accepted November 15, 2008; Published December 9, 2008
Copyright: ß2008 Thomas et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: We gratefully acknowledge the financial support of the Institute of Natural Resources, Massey University. The funder had no role in study design, data
collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: j.d.holland@massey.ac.nz
Introduction
The 650 km
2
Sabi Sand Reserve (SSR) is an association of 17
freehold game lodges and private game reserves sharing a
common 50-km unfenced eastern boundary with Kruger National
Park (KNP). Together, they form 20,650 km
2
of undisturbed
savanna, woodland, mountain terrain and riverine forest, and are
home to 490 bird species, 147 mammals, 94 reptiles, 33
amphibians and 200 tree species [1]. The reserves are in the
north east of South Africa where KNP is bordered by
Mozambique to the east and Zimbabwe to the north.
At one time, the study area was a popular hunting region where
elephants were heavily targeted. However, after its establishment
as a South African Government Reserve in 1898, and KNP in
1923, elephants began to recolonise the area. Both KNP and SSR
are managed as autonomous units with the former answerable to a
conservation minister and the latter to private shareholders.
The fence between KNP and SSR was dropped in 1993 after
which elephant numbers in SSR increased rapidly from 60 to
1,398 (2.15/km
2
) by 2007, an average annual increase of 13.8%.
This compares with 3.9% per annum in KNP where elephant
numbers during the same period rose from 7,834 to 13,050 (0.65/
km
2
) [2]. The increase in elephant numbers has led some scientists
to fear that continued growth will result in tree canopy destruction
that may exacerbate reductions in species richness of birds and
other taxa [3,4].
In 1989, Whyte [3] concluded that effective elephant manage-
ment policies in KNP should be supported by a better
understanding of elephant movement patterns. Consequently,
Whyte used radio transmitters to study the movements of 29 adult
KNP elephants during a seven-year period to 1996 [3]. He tracked
each elephant for an average period of four years and, using an
average of 10 location points each year, identified home ranges
varying from 45 km
2
to 1800 km
2
and observed that movements
were not always confined within individual parks. In 2006, the
paucity of elephant movement data were highlighted by a panel of
scientists who reported that a more precise understanding of
elephant movements are required if successful management
programmes are to be developed [4].
In our study we tracked the daily movements of the study
animal for five years to further understand the location, size and
inter-annual variability of home ranges; identify travel corridors
between parks; and consider how the resources within the reserves
influence movement.
Materials and Methods
In conjunction with the Sabi Sand ecologist and staff from
KNP’s Scientific Services and Veterinary Wildlife Services, a
breeding herd cow was identified and darted from a helicopter on
the 26 September 2003 and a satellite collar attached. Before the
batteries of the tracking collar expired, the animal was retagged on
15 August 2006. Observations of daily movements since the
retagging showed no obvious signs of stress as there were no
changes in the daily movement patterns. In previous studies, the
matriarchs of the family group were selected [3], however, because
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these are the oldest animals and susceptible to a higher mortality
[3], we selected a younger, lactating cow, estimated to be 24 years
old with a small calf at foot (see Figure 1). The study animal is a
member of a matriarchal group of three adult and four juvenile
elephants.
We tagged the elephant on a cool day to avoid overheating and
death of the animal. The tranquiliser dart was fired from a
modified shotgun at the rump using a 24 cm67 ml aluminium
syringe dart with a 3 mm ‘collared’ needle. The drug combination
used to tranquilize the lactating cow was short-acting Azaperone
(Janssen Pharmaceutica) and the analgesic etorphine hydrochlo-
ride or M99 (Norvartis) with Diprenorphine or M-5050 as an
anaesthetic and antidote respectively [3,5]. Upon the elephant
becoming recumbent, the rest of the matriarchal group was
herded off to a safe distance by the helicopter.
The helicopter team was accompanied by a ground crew to roll
the immobilized elephant on its side in the event it collapsed on its
haunches after tranquilising. The pressure from the weight of the
elephant upon the diaphragm and sternum may have injured or
killed the animal [5]. The elephant’s exposed eye was covered with
its ear to protect it from direct sunlight and dust and the trunk was
extended to ensure the animal breathed comfortably.
Equipment
A combination of satellite receivers and a GPS transmitter were
used to monitor the elephant’s movements. The Inmarsat 3 F1 is a
third generation satellite (1996) covering the whole of Africa,
Australia and Middle East [6].
The tracking unit attached to the elephant had a GPS receiver
and a VHF radio transmitter incorporated into the collar. The
unit on the elephant was set to obtain and transmit a single
location signal at noon (local time) each day. We monitored the
period 26 September 2003 to 30 July 2008, equating to
approximately 1,750 tracking-days.
The location data were mapped and analysed using ArcGISH
ArcMapH9.2 (Environmental Systems Research Institute, Red-
lands, California, USA), with Spatial AnalystHand Tracking
AnalystHextensions. Home range area was determined by
calculating the Minimum Convex Polygon (MCP) using Animal
Movement Analyst Extension (AMAE) [7]. A MCP is known to
inflate the actual area occupied by the animal because it includes
outliers. According to Kenward [8], however, a MCP including all
locations is the most widely used home range estimator allowing
for meaningful comparisons between home ranges of different
studies. This being the case, we calculated home range using a
MCP with all the locations for our study animal and, to allow for a
more conservative estimate, recalculated it with 95 and 50% of the
locations. Outliers were removed with AMAE utilising the
harmonic mean method [9].
Weather data were obtained from the South African Weather
Bureau station at Skukuza. The station is located within the study
area and recorded average annual rainfall and temperature of
541 mm and 23.8uC respectively during the five-year period.
Summer is the rainy season and winter is the dry period when the
animals become increasingly dependant upon waterholes and
manmade dams. This is true for most African national parks [10–12].
Habitat study
We mapped daily location points to identify core winter and
summer home ranges through which transect lines were surveyed to
further understand the fine scale of the predominant landscape and
vegetation representative of the home ranges. The SSR and KNP
transect lines (Figure 2) were 28 km and 20 km long respectively
and sampling was conducted at one kilometre intervals. Vegetation
and landscape attributes within a 30-meter radius of each study site
were recorded. The SSR home range area was shown to be more
biologically diverse. Dominant tree species in both areas include
knob thorn Acacia nigrescens, sickle bush Dichrostachys cinerea and russet
bushwillow Combretum apiculatum. Guinea grass Panicum maximum is
ubiquitous to both home range areas.
Results and Discussion
Habitat use
The elephant’s daily location points are mapped in Figure 2,
showing the concentrations of location points within each park.
We found that the elephant in this study did not use the
available habitat randomly, instead developing a strong preference
for a specific habitat while others were seldom, if ever, used. These
findings are similar to those of Ntumi, van Aarde, Fairall, and de
Boer [13].
Seventy two percent of all positions recorded during the
summer months (December, January and February) were located
within KNP and 77% of winter positions (June, July and August)
were located within SSR. Average monthly visitation rates to KNP
over the five-year period peaked at 20 days during December and
January before the herd moved to the well-watered SSR in June
when visitation rates are highest (23 days) and coincide with lowest
average rainfall and temperature (Figure 3).
Using the distance between consecutive mid-day locations as a
proxy for daily distance travelled by the elephant, we found that it
walked an average of 127 km per month during summer
compared with 101 km per month during winter (paired-sample
t= 2.25, df = 3, P,0.05). Whilst it is difficult to attribute changes
in behaviour to specific variables, or combinations of variables, we
found that the study elephant’s movement increased as temper-
ature increased (r = 0.71; P,0.001; Figure 4). This is most likely
because the coldest months are also the driest and, given that
elephants need to drink every day or two [4] they move to their
winter home range where there is a high density of waterholes, so
less movement is necessary.
Within SSR, the study elephant barely utilised the eastern
boundary with KNP and a small pocket in the south west of SSR
(Figure 2). This may be attributable to the limited number of
eastern border waterholes [14] and the large human presence near
the unutilised south west pocket of the SSR.
Figure 1. Study elephant with satellite tracking collar (Photo J
Holland).
doi:10.1371/journal.pone.0003902.g001
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In June 2007, landscape and vegetation transects were
conducted in the core home ranges and 33 tree and 21 grass
species were identified in the SSR and KNP home ranges
respectively. The SSR home range was more biologically diverse
with 30% of the trees and 57% of the grasses found in SSR not
represented in the KNP transect samples (Table 1).
Figure 2. Study area and daily locations of study elephant. Map of KNP, South Africa showing the locations of daily GPS fixes from the study
animal obtained from September 2003 to July 2008.
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This may explain the elephant’s preference for the undulating
granite/gneiss and gabbro plains of SSR during winter while the
summer, rain-charged rivers of the Karoo Sediment home range
plains in KNP may be one of the reasons that the elephant targets
this landscape and vegetation type. During the rainy season the
elephant selects from a narrower choice of habitats. At this time of
the year, the plants in KNP elephants’ diet decrease [13]. Codron
et al. [15] have shown that elephants in the study area tend to
become dependant upon grass during summer, with tree-felling
and debarking of larger trees starting in winter when the grass
dries and the elephants begin eating woody plants. This response is
intensified during draught periods [4,16]. We agree with Ntumi et
al. [13] who stress that most elephants favour closed canopy
habitat types like riparian thickets and vegetation types associated
with water.
Our findings concur with those of Smit, Grant and Whyte [17],
namely, that the herd occurred closer to water sources more
frequently than would be expected if they were randomly
distributed. The observed locations were significantly closer to
waterholes and rivers in both KNP and SSR than random
locations (Figure 5).
By 2007, SSR had 376 waterholes or 0.58 waterholes per km
2
and 2.15 elephants per km
2
compared with a KNP density of 0.65
elephants per km
2
. This, in conjunction with improved winter
browsing and a well-distributed, reliable water supply make the
SSR an attractive winter destination. Elephants in KNP consume
varying proportions of browse to grass in different seasons [15]
and it may be that the wider diversity of woody plants in the study
animal’s winter home range allows elephants to utilise this
resource more efficiently after grass production drops off following
the dry summer. During the wet summer, elephants increase their
grass consumption to around 50% and then change over to the less
varied summer diet [15,18].
Home range
The distance between the core summer and winter home ranges
was 32 km. The 95 and 50% MCP combined home ranges for
KNP and SSR were 2,244 km
2
and 783 km
2
respectively.
Comparable results from KNP from Whyte’s [3] study of 29
radio-tracked elephants give 90% MCPs ranging from 45 to
1,800 km
2
. While our results align with his upper estimates his
overall results will tend to be low because he used only 10 locations
per year.
The elephant’s five-year SSR winter home range was 308 km
2
and its annual average home range during the same period was
131 km
2
. This shows that, whilst the elephants move back to the
Figure 3. Average monthly occupancy rates. The average monthly occupancy of the study elephant within Kruger National and Sabi Sand Parks
compared to average monthly temperature (uC) and rainfall (mm) from September 2003 to July 2008.
doi:10.1371/journal.pone.0003902.g003
Figure 4. Average monthly distance and minimum tempera-
ture. Distance is based on a single GPS location taken at noon each day
and average minimum temperature for the period 1960–1990 from the
Skukuza weather station.
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same broad geographic area each year, only 40% is utilised during
any one year. The five-year KNP summer home range was
1,139 km
2
and its annual average home range for the same period
is 424 km
2
. The annual average home range within SSR is in line
with the findings of Fairall [19] for the same reserve (,200 km
2
).
Also our estimates for the KNP home range is similar to reports by
Whyte (523 km
2
) and Hall-Martin (436 km
2
) in 2001 and 1984
respectively [13].
Table 1. Dominant tree and grass species identified in vegetation transect through elephant home ranges in Kruger National and
Sabi Sand Parks (June 2007)
1, 2
.
DOMINANT SPECIES SOILS AND TOPOGRAPHY SSR
(n = 28)
KNP
(n = 20)
No.
3
% No. %
TREES
Euclea divinorum Magic guarri Mostly found in the brackish flats in granite & alluvial soils along river courses.
Generally growing in pockets among other tree species, in thorn scrub, hillsides
& woodland.
19 68 5 25
Acacia nigrescens Knob thorn Usually occurs in groups. The largest trees are found in the flood-plains
& shrub form is common in the gabbro & basalt areas.
16 57 1 5
Dichrostachys cinerea Sickle bush Prefers clay-like soils but also found on all soils & close to rivers & brackish
flats. Also along roads due to increased run-off.
16 57 11 55
Combretum hereroense Russet bushwillow Most often seen around pans, rocky areas & sometimes on stream banks.
Usually occurs in closely associated groups.
14 50 13 65
Ziziphus mucronata Buffalo thorn Found everywhere but prefers brackish flat & koppie, open woodland, often
in alluvial soils & on termite mounds.
12 43 0 0
Sclerocarya birrea Marula Common throughout the Lowveld, growing on all soil types. 12 43 7 35
Combretum apiculatum Red bushwillow Often found on granite crests. As with the mopane, the red bushwillow is one
of the most abundant trees in area.
82915
Lonchocarpus capassa Apple-leaf Common in most parts, grows on all soil types, tallest & most plentiful on
alluvial plains & on river & stream banks.
7251365
Acacia nilotica Scented thorn Prefers brackish soils near rivers & drainage lines. Also found on clay soils. 7 25 4 20
Terminalia sericea Silver cluster-leaf Found in granite area, prefers deep, well-drained, sandy soils. Prolific on
mid-slope seep-lines where it grows in dense groups. Common in higher
rainfall areas.
62100
Grewia monticola Silver raisin bush Small to medium size deciduous tree 2–10 m. Occurs over wide range of
altitudes in riverine fringes & open woodland - often on termite mounds.
518525
Spirostachys africana Tamboti Occurs on all soil types, common in the Lowveld. Often in groups of a few
big trees along rivers or streams in the brackish flats.
518525
Peltophorum africanum African weeping wattle Grows best in lower altitudes in wooded grassland & on well-drained sandy soils,
but occurs on all soil types in area.
518420
Diospyros mespiliformis Jackal berry Grows along most river courses & bigger streams at lower altitude woodlands.
Often found growing away from drainage lines & on termite mounds.
518420
GRASSES
Panicum maximum Guinea grass Tufted perennial, grows on all soils; damp places along fertile soil; shade of
trees & along rivers.
17 61 16 80
Heteroptogon contortus Spear grass Fast-growing grass that likes well-drained stony soils; open areas; twisted
seed-heads are often seen along roadsides.
9321155
Digitaria eriantha Finger grass Tufted perennial that grows in open areas & on moist soils - especially in
sandy areas.
829630
Pogonarthria squarrosa Sickle grass Perennial that grows in well-drained sandy soils. Common in disturbed
places - an indicator of poor, sandy soils, old lands.
82900
Perotis patens Cat’s tail grass Tufted perennial that grows on disturbed soils, often in poor sandy soils
and dry exposed sites.
518735
Setaria Sphacelata Torta Creeping bristle grass Creeping perennial grass that likes granitic, well-drained soils. Good soil
conservation grass that forms runners that bind soil.
5181155
Dactyloctenium australe L.M. grass Creeping perennial that thrives in shade in sandy soil. Popular lawn grass
in Lowveld.
41400
Themeda triandra Red grass Tufted perennial that grows on basalt, gabbro and dolerite and undisturbed
grassland areas.
41400
Chloris virgata Feather top chloris Variable annual grows in shade but prefers open country. Not drought tolerant. 3 11 0 0
1
Fyvie [21].
2
A total of 33 tree and 21 grass species were identified in SSR and KNP.
3
Refers to the number of times species were identified in the 28 SSR transect location sites.
doi:10.1371/journal.pone.0003902.t001
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In Table 2 the details of the study animal’s movements between
SSR and KNP over the five-year period are presented, revealing
that only eight of the 26 habitation periods were less than a month
in duration. The cow moved between the two home ranges up to
three times a year. The average annual winter home range size in
SSR is 195 km
2
compared with 331 km
2
for its summer
counterpart in KNP and, as can be expected, the home range
increases with the time the elephant spends in each reserve
(r = .78, p,0.002 for SSR; r = .61, p,.03 for KNP). From tracking
the elephant’s movement between the two reserves, a northern
and southern corridor were identified (Figure 2). Between
November 2003 and April 2008, the corridors were traversed on
25 occasions with the busier northern corridor used for 78% of the
crossings. Notably, all the movements from KNP to SSR were
through the northern corridor.
Management implications
This study followed a single female, and consequently her group
of three adults and four juveniles, for a period of five years. While
this long duration is not a substitute for extensive replication, this is
the first KNP/SSR elephant to be tagged with a satellite collar
and, being the longest continuous study of its kind in the area, the
results provide the first insight into within- and between-season
movements. It is known that female elephants live and travel
Figure 5. Observed and random location distances from water sources. Random points were generated within the 95% MCP for the KNP
and SSR home ranges. For both observed elephant locations and random points, the distance to the nearest water, either waterhole or river, was
calculated.
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within distinct matriarchal groups each led by closely related
matriarchs who may be sisters or cousins and, together, the groups
form part of a wider composition known as a ‘bond group’.
Therefore, movement of one adult female could be extrapolated to
the movements of a matriarchal group. Two similar elephant
tracking studies are currently being undertaken by Thomas, Minot
and Holland in the same study area and the data from the first 18
months of this on-going research support the findings of this study.
Namely, that both move between the two parks, summer MCP
home ranges are larger than winter home ranges and both are
utilised in the same manner as reported in this study.
This long time series has enabled us to report on the reciprocal
importance of KNP and SSR to the elephant and its attendant
herd and that since the fence between the two reserves was
dropped, the elephants consistently rely upon KNP for summer
grazing and SSR for winter grazing and water. It has also enabled
us to identify possible important northern and southern corridors
between the reserves. This, combined with the rising number of
elephants in both reserves signals the importance of ongoing co-
operation between wildlife managers from both reserves.
In 1999, SANParks approved a new policy for managing the
KNP elephant population based upon the park being divided into
zones and managed according to biodiversity impacts rather than
on fixed elephant numbers [2,3]. These were designed to broadly
conform to home ranges that were identified using radio-collared
elephants of herds in selected zones [2,20]. However, the radio
data were limited to less than one location point per month and,
notwithstanding the valuable contribution of this early research to
understanding elephant movements at a broad level, it would not
have been possible to identify specific movement corridors
between home ranges; isolate shorter visits made by animals to
home ranges; identify movement patterns between home ranges;
and map the full extent of an elephant’s home range.
Future management plans could be more comprehensive by
recognizing that the two areas must be managed as a single unit.
From the results of our study, we conclude that the boundary
recommended for the southern high-impact region [3] would only
accommodate the elephant’s summer home range. The proposed
‘high-intensity’ elephant zone does not include the elephant’s SSR
winter home range area. Both KNP and SSR share similar
challenges associated with overpopulation, the provision of
artificial waterholes, and monitoring and evaluation of flora and
fauna. Therefore, a co-operative management plan taking into
account seasonal elephant use of both parks, and the corridors
between them, should be a priority.
This study illustrates the advantages of long-term continuous
monitoring of wildlife in both better understanding their seasonal
ecology and formulating management plans based on their habitat
requirements throughout the year.
Acknowledgments
We warmly thank Jonathan Swart, Gavin Hewlett and Johnson Mahluli
(Sabi Sand Reserve); Dr Ian Whyte (KNP Scientific Services), Hennie de
Waal (pilot), Dr Peter Buss (KNP’s Veterinary Wildlife Services); and Sarah
Holland for their assistance with the field research.
Author Contributions
Conceived and designed the experiments: BT JH. Performed the
experiments: BT JH. Analyzed the data: BT JH EOM. Contributed
reagents/materials/analysis tools: BT JH EOM. Wrote the paper: BT JH
EOM.
Table 2. Park and corridor usage of SSR and KNP.
Sabi Sand Reserve Kruger National Park
N
1
Departure Date
2
95% MCP (km
2
)
3
Departure corridor
4
N Date 95%MCP (km
2
) Departure corridor
4
37
5
3 Nov 03 115 Southern 7 10 Nov 03 127 Northern
45 25 Dec 03 220 Northern 108 11 Apr 04 485 Northern
189 16 Oct 04 322 Southern 91 13 Jan 05 514 Northern
196 29 Jul 05 447 Northern 31 29 Aug 05 177 Northern
7 5 Sep 05 20 Northern 59 3 Nov 05 230 Northern
27 30 Nov 05 180 Southern 37 6 Jan 06 341 Midway
6 12 Jan 06 68 Northern 54 8 Mar 06 547 Northern
128 12 Jul 06 288 Northern 50 1 Sep 06 235 Northern
84 24 Nov 06 340 Southern 83 15 Feb 07 188 Northern
6
46 1 Apr 07 149 Northern 22 24 Apr 07 242 Midway
160 1 Oct 07 137 Northern 19 20 Oct 07 192 Northern
14 3 Nov 07 35 Northern 71 11 Jan 08 624 Northern
7
98 18 Apr 08 209 Northern 47 5 Jun 08 403
Ave MCP 195 331
5-year MCP 308 1139
1
Number of days within the park before movement.
2
Date that elephant started journey to other home range.
3
The MCP (km
2
) is based on locations obtained inside the relevant park calculated after arrival date from previous home range.
4
Refer to Figure 2 for corridor location.
5
From 26 September onwards.
6
Entered corridor via Manyeleti.
7
Entered corridor via Timbavati.
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