In a classic example of adaptation to a harsh environment these lions exhibit
unique ... data for the desert adapted lions of the Kunene Region, Namibia.
Research Report October 2003
Population ecology of desert-adapted lions in the Kunene Region, Namibia
Photo: Flip Stander
Report by:
P. Stander
&
Ministry of Environment and Tourism Private Bag 13306, Windhoek, Namibia
L. Hanssen
Predator Conservation Trust Box 90427, Windhoek, Namibia
INTRODUCTION Namibian lions live at low densities and maintain large home ranges in an arid to semi-arid environment (Stander 1991; Nowell & Jackson 1996). In a classic example of adaptation to a harsh environment these lions exhibit unique behaviour, such as individual specialisation and cooperative hunting in Etosha (Stander 1992) and killing seals along the Skeleton Coast (Bridgeford 1985). Lions are of great aesthetic appeal and financial value due to the growing tourism industry in southern Africa. Alarmingly, there is a shortage of reliable and accurate data on their population dynamics and conservation status. It is therefore imperative that sound baseline data on density, demography and ecology be collected to guide the development of long-term conservation strategies. This study aims to provide such data for the desert adapted lions of the Kunene Region, Namibia.
STUDY SITE
The study site of 15 440 km2 is situated in the Palmwag tourism concession and extends into the Skeleton Coast Park and surrounding communal conservancies of the Kunene Region. The area falls in the Etendeka Plateau landscape of the northern Namib Desert, with an annual rainfall of 0 - 100 mm (Mendelsohn et al. 2002). The study area stretches from the Atlantic Ocean in the west to the edge of human settlement and livestock farming in the east. The Hoaruseb river runs along the northern boundary and Springbok river in the south.
Skeleton Coast Park
Etosha National Park
Hoaruseb river
Hoanib river
Kunene Study Area
Low density High density study area study area
Uniab river
#
Namibia
2
% Palmwag
METHODS
Lions in the Kunene are difficult to locate and observe. To overcome this difficulty all known adult and sub-adult lions are captured and fitted with a radio-collar. The study area is covered systematically by tracking spoor, setting out bait and using sound play-backs to locate and capture individual lions. During immobilisation, following standard procedures (Stander & Morkel 1991), lions are marked with permanent brands and age is determined from tooth wear and eruption (Smuts et al. 1978). Radio-collared animals are located with the use of a fixed-wing aircraft. Aerial locations are then followed up by ground observations to record group composition in relation to individuals and age/sex structure, and the ratio of marked to unmarked individuals. Home range analyses is based on locating the daytime resting spots of lions by radio telemetry with at least 24 hours between fixes. Home range size is calculated using the Minimum Convex Polygon (MCP) and Kernel Contour methods (Harris et al. 1990).
Lions feeding on a bait in Barab River
Photo: Lise Hanssen
Lions are aged by tooth wear
Photo: Lise Hanssen
Community members assist with radio collaring Photo: Flip Stander
A lion is photographed from the air during tracking Photo: Flip Stander
RESULTS Socio-ecology and population dynamics Since November 1999 we have radio collared 23 lions and a total of 48 lions are marked or individually identifiable . There are four distinct groups or prides of which the Barab/Aub pride is the largest (Genealogy chart). There are presently 20 animals in the group. All the adult lions from both the Uniab nomad male group and the Hoaruseb group were born in the Barab/Aub pride but they have now separated permanently from the pride.
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Two additional sub-adult groups, Xpl-19, 20 & 21 (cubs of Xpl-2) and the first litters of Xpl-9 and 11 (6 lions), have recently left the pride and we are monitoring their movements. The Obab pride appears independent and distinct from the Barab/Aub pride. The Obab pride consists of eight lions but we have substantial evidence that they form part of a larger pride. All individuals in the same pride have largely overlapping home ranges but they regularly spend long periods apart. Adult lionesses of the Barab/Aub pride frequently spend more than six months apart and a separation of three years was recorded between several of the pride females. Such long separations are unusual in lion social behaviour. The typical fission-fusion strategy has a frequency pattern that is measured in days (Schaller 1972). We suggest that this unusual fission-fusion characteristic is a behavioural adaptation to the demanding condition imposed by the desert habitat. More data need to be collected to address this hypothesis.
Some individual lions in the Kunene population
Aerial view of Xpl-9, Xpl-11 and 6 large cubs
Sub-adult male Xpl-3
Xpl-1
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Photos: Lise Hanssen
Group structures and genealogy of the Barab/Aub pride and related groups between November 1999 and July 2003 Barab / Aub Pride Xpl-1
Xpl-2
Xpl-5
Xpl-9
Xpl-11
Xpl-14
? Litter died
Xpl-19
Xpl-20
Uniab nomad males
Xpl-21
Xpl-4
Xpl-8
Xpl-12
Xpl-13
Hoaruseb group Xpl-10
Key:
Xpl-3 Xpl-6
Adult
Female
Sub-adult
Male
Cub
? = Mother unknown
Mortality
Xpl-15
Sex unknown
Group structure and genealogy of the Obab pride between March 2001 and July 2003.
Obab Pride Xpl-17
Xpl-18
One cub died when < 3 months old Xpl-16
Xpl-23
Xpl-22
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Of the seven radio-collared lionesses, six (85%) presently have dependant cubs. There are 16 cubs in total at an average of 2.8 cubs per female. The population dynamics of these lions were evaluated over a five year period (19992003) by analysing birth rates, mortality, fecundity and rate of increase associated with 13 known adult lions. This population of 13 known lions in 1998 increased at an average rate of 22.5% (range 14.6 – 34.5%) to 48 lions in 2003, where the sex ratio is even. Population density was calculated in two intensive study areas (Study site map) that were surveyed intensively and where we were confident that there were no unmarked or unknown lions. We predicted that the western study area would support a lower density of lions since the habitat is significantly dryer and supports lower numbers of prey species than the eastern study area. Using the Kunene Sampling Method (Loveridge et al. 2001) lion densities were calculated at 0.49 lion 100 km-2 for the low density area (west) and 0.71 lion 100 km-2 for the high density area (east). Extrapolating these two density estimates, as a range of minimum to maximum, to the total study area the population estimate is between 76 and 109 lions.
Population demography of the Kunene Lions Total Study Area (km2)
15440 2
High density study area (km )
875
Low density study area (km2)
770
Number of marked and individually known lions
48
Number of radio-collared lions
23
Lion population estimate
Low density
High density
Calculated number of lions in study sites
3.8
6.2
Lion density per site (lions 100 km -2)
0.49
0.71
76
109
Extrapolated estimate for Total Study Area
S e x r a tio o f K u n e n e lio n s
M a le F e m a le
8 6 4 2 0
A d u lt
S u b -a d u lt
During the five year period six lionesses gave birth to 13 litters totalling 38 cubs. Litter sizes ranged between 2 and 5 cubs with the mean at 3.1 cubs. Cub survival was high, with only 9% mortality up to age of one year (n = 38) and none thereafter. With most cubs surviving, the mean birth interval was 2.2 years (SD = 0.28; range 1.9 – 2.7 years; (n = 6).
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With this remarkably high fecundity rate there is a preponderance of young lions in the population when looking at an age distribution graph for 2003. However, when the same data is cast into broader age classes the result depicts the characteristics of a healthy and stable population.
A g e d is t r ib u t io n o f t h e K u n e n e lio n p o p u la t io n 12
10
Numbers
8
6
y = - 3 .7 7 4 1 L n ( x ) + 1 0 .1 6 3 R 2 = 0 .5 5 3
4
2
0 1
2
3
4
5
6
7
A g e
8
9
10
11
12
13+
(y e a rs)
D is trib u tio n o f a g e c la s s e s in th e K u n e n e lio n p o p u la tio n 16 14
Numbers
12 10 R 2 = 0.9739
8 6 4 2 0 S m a ll c u b s (< 1 y rs )
L arg e c u b s (12 y rs )
S u b -a d u lt s (2 4 y rs ) A g e C l a sse s
7
A d u lts (4 -10 y rs )
P a s t p rim e (> 1 0 y rs )
The phenomenal increase of this lion population during the study period is best presented as a logarithmic rate of increase (top) and the annual exponential growth rate (bottom). Population growth was over 30% for both 1999 and 2000. Thereafter it dropped to around 15% for 2001, 2002 and 2003.
T h e r a te o f in c r e a s e o f th e K u n e n e lio n p o p u la tio n 4.00
loge Numbers
3.50
y = 0 .6 9 4 5 x - 13 8 7 .4
3.00 2.50 2.00 1.50 1.00 0.50 0.00 19 99
2 000
2 00 1
20 02
20 03
2004
T im e (y e a r s)
E x p o n e n t ia l r a t e o f g r o w th o f t h e K u n e n e lio n p o p u la t io n 0.45
loge Exponential rate of increase
0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 1999
2000
2001 Ye a rs
8
2002
2003
Home ranges
Home range sizes are large and range between 626 - 3438 km2 (Kernel method). The southern and northern home ranges for Xpl-10 and the Xpl-3 subgroup were calculated separately as they were born and spent time in the southern area before dispersing to the north. The number of radio tracking fixes for the Agab pride, the Xpl-3 subgroup, Xpl-10 and the Xpl-19 subgroup are insufficient for calculations since home range estimates increase with additional data. Notwithstanding Kunene lions occupy home ranges larger than in other documented studies. Pride / group
ID
Barab / Aub
Hoaruseb
Group description
Accuracy of fixes
Home range (km 2)
N
MCP
Kernel (95%)
XPL-1 XPL-5
Single male Female & cubs
92 82
1440 2012
650 2460
76% 62%
XPL-2
Female & cubs
81
1792
3422
74%
XPL-9 & 11
Female & cubs
70
1224
1347
72%
XPL-19
Sub-adults
13
939
1407
Negative
XPL-10 South
Sub-adults
39
2235
2989
Negative
XPL-10 North
Female & cubs
26
1378
1223
Negative
XPL-3 South
Sub-adults
50
2378
3438
Negative
XPL-3 North
Male group
29
122
626
52%
XPL4
Male group
70
2573
2447
80%
XPL-17
Female & cubs
35
1493
2536
Negative
XPL18
Female & cubs
26
1294
2327
Negative
Uniab nomads Obab
MCP = Minimum Convex Polygon *The percentage of fixes where the MCP home range estimate reached an asymptote of at least 95% of the total MCP estimate, based on bootstrap analyses.
Locations and home ranges (Kernel contours) of individuals and sub-groups (See key on page 11) Xpl-1
H oa
ive n ib r
Xpl-5
r H oa
ive n ib r
r
# #
#
#
Kai-as # Lion % Project Camp
Obab # river
# # # # ### ## ## ## # ## ## # # # # # ## ## # ## # ### # # # # # # ## # # # ## # # # # ##
#
# #
Hunkab # rk Pa
## #
#
Aub river
# # %
Palmwag
#
Palm
##
#
# # # # # # ## ##
Aub river # #
# #
Sk
e Sk
t as Co n o le t
rk Pa
Hunkab #
#
#
# # Kai-as ## # # # # # # # # # # ## # # # # # Lion % ## ## # # # % Project ## # # # Camp #
st oa nC o t e le
#
Palmwag
Obab river
# # ##
Palm
#
#
## Kaikams ## # ###
Kaikams
riv e r U n ia b
riv e r U n ia b
9
Xpl-19 sub-adult group
ive n ib r
iver nib r H oa
r
#
rk Pa t as Co
# #
##
# # #
ton ele Sk
Lion % Project Camp
%
# #
Palmwag
#
Palm
Obab river #
# # Aub river # # # # # # # ## ### # # # # # # # # # # # # # ### Kai-as ## # # # # # ## # # # # # # Lion % ## #
Hunkab #
#
Kai-as #
#
#
Aub river
Hunkab #
#
#
a rk tP oas C ton ele Sk
H oa
Xpl-9 and Xpl-11
#
Project Camp
Obab river
Palmwag
#
Palm
#
Kaikams
#
riv e r Un iab
%
##
Kaikams
river Uniab
#
Xpl-10 (north and south)
Xpl-14
iver nib r Hoa
#
#
#
# # # ## # # # # # #
#
Purros
#
Hunkab #
#
Sesfontein %
# #
# # r ### ib ri#ve Hoan # # ##
Mowe Bay %
# #
Hoanib river
# # # # # ## ## # # #Aub river # # # # # # # # Kai-as #
as t Co
k Par
Hunkab ##
on let Ske
river
Aub river #
rk Pa ast o C ton ele k S
# # # Hoaruseb #
# # ## ##
Lion % Project Camp
Obab river
# # # # # # # # # ## Kai-as # ## # # # # # ## # # # # ## # ### Lion % # # # ## Project % Camp # # ## Palm # Obab # # ## ### ## # river # # # # # # ## # # # ## # ## ##Kaikams # ## # ## #
Palmwag
river Uniab
#
Palmwag %
# Palm
#Kaikams river Uniab
Uniab river
10
# #
Xpl-18
H oa
ive n ib r
r
Aub river
el Sk
a rk tP oas C n eto
Hunkab # ##
#
Kai-as #
#
#
#
#
# Lion # % #
Project Camp
%
Key
Palmwag
#
Palm
#Obab ## #
▲
river
## #
#
# #
#
#
Locations
#
Kaikams
65% kernel contour
river Uniab
80% kernel contour 95% kernel contour
The locations of Xpl-9 and Xpl-11 (▲) have been superimposed on a satellite image showing the topography of the upper Aub/Barab river. In the next phase of the project, we will incorporate this technology to evaluate habitat use and preferences of the Kunene lions.
$ $
$
$$ $
$ $ $
$
$
$ $
$ $ $ $ $
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Dispersal Developing conservation strategies for the Kunene lions is, among many ecological parameters, dependant on a sound understanding of the factors that drive the distribution and dispersion of the population. Monitoring the dispersal of individuals from their maternal home ranges provides important information towards understanding these population characteristics. During the present study we monitored the dispersal of six groups of lions. All the groups, with the exception of the most recent dispersal (Xpl-19 group), have settled in a new home range. With the exclusion of the Xpl-19 group, the lions moved an average of 104.6 km (SD = 30.8) from their maternal home range. More data will be collected to allow analyses on the temporal and spatial patterns of dispersal . Group composition
Date occupying maternal home range
Direct distance to present home range (km)*
Adult male
1998
120
Adult females
1998
85
Xpl-3,6 & 15
Adult males
1999/2000
130
Xpl-10
Adult female
1999/2000
128
Xpl-4,8 & 12
Adult males
1999/2000
60
Xpl-19,20 & 21
Sub-adults
2001
51
Lion ID Xpl-1 Xpl-5 & 9
#Purros
Etosha National Park
Xpl-3 Xpl-10
Xpl-1
Sesfontein
%
Hoaruseb river
Xpl-5,9
iv er nib r Ho a
Mowe Bay
%
Xpl-19 Hoanib river
Xpl-3,4,10,19
Hunkab t Pa o as nC o t e l Ske
rk
#
Aub river
#
% Xpl-1,5&9 %
Lion Project Camp
Palmwag
Obab river
Xpl-4 b river Uni a
Key
# Aub Canyon
Kai-as
Uniab river
Maternal home range Home range during 2003
12
#Kaikams
CONCLUSION
This desert adapted and coastal roaming lion population were believed to have disappeared totally after a number were killed by pastoralists in 1988. The results from this study therefore unveil significant features and characteristics of the population. These lions likely live in the most rugged and arid environment anywhere in Africa. The long-term monitoring of individually known lions allowed qualitative assessment of important socio-ecology, population demography and movement characteristics. Some aspects of their behaviour and ecology is markedly different to lions elsewhere. Under these low density conditions Kunene lions produce larger litters (3.1 cubs) than measured elsewhere in Africa (2.4 cubs, Schaller 1972), and cub survival is unusually high. These features contributed to an astounding growth-rate and population increase. We propose that this is due to several years of good rainfall and stable, resident prey populations. The lions live in the largest home range sizes previously recorded, and perhaps as a result, pride members spend long periods apart. Sub-groups of a pride may spend many months apart which contradicts markedly with the daily fission-fusion patterns recorded elsewhere in Africa (Schaller 1972). We suggest that these behavioural and ecological differences are adaptations to the demanding habitat. We intend to continue intensive monitoring over the next five years to identify the mechanisms that drive adaptation. Sound baseline data and long-term monitoring of population dynamics, ecology and conflict with pastoralists will form the basis of a conservation strategy for the protection and sustainable use of these remarkable lions.
REFERENCES
Bridgeford, P.A. (1985). Unusual diet of the lion Panthera leo in the Skeleton Coast Park. Madoqua. 14: 187-188. Harris, S., Cresswell, W.J., Forde, P.G., Trewhella, W.J., Woollard, T. & Wray, S. (1990). Home-range analysis using radio-tracking data - a review of problems and techniques particularly as applied to the study of mammals. Mammal Rev. 20: 97-123. Loveridge, A. J., Lynam, T. and Macdonald, D.W. (Eds). (2001). Lion Conservation Research. Workshop 1: Survey Techniques. Wildl. Conserv. Unit. Pp: 2-4. Mendlesohn, J., Jarvis, A., Roberts, C. & Robertson, T. (2002). Atlas of Namibia : A portrait of the Land and it’s People. David Philip Publishers, Cape Town. Nowell, K. & Jackson, P. (1996). Wild cats: status survey and conservation action plan. IUCN, Gland, Switzerland. Schaller, G.B. (1972). The Serengeti Lion. Chicago: University of Chicago Press. Smuts, G.L., Anderson, J.L. & Austin, J.C. (1978). Age determination of the African lion (Panthera leo). J. Zool., Lond. 185: 115-146. Stander, P.E. (1992). Foraging dynamics of lions in a semi-arid environment. Can. J. Zool. 70: 8-21. Stander, P.E. (1992). Cooperative hunting in lions: the role of the individual. Behav. Ecol. Sociobiol. 29:445-454. Stander, P.E. & Morkel, P.vdB. (1991). Field immobilization of lions using disassociative anaesthetics in combination with sedatives. Afr. J. Ecol. 29: 138-148.
ACKNOWLEDGEMENTS
The Kunene Lion Project received financial support and assistance from the Ministry of Environment and Tourism, Namibia Nature Foundation, Fort Worth Zoo (USA), Dunlop (Namibia), Total (Namibia), Save the Rhino Trust, IRDNC, WWF - LIFE Program, The Gun Shop, Brookfield Zoo (USA), Wilderness Safaris, Colchester Zoo (UK) and the Predator Conservation Trust in the UK. Mr Jo Tagg (DEA) kindly provided satellite images.
REPORT CREDITS
Data analyses & GIS - P Stander; Layout - L Hanssen; Field work - L Hanssen, P Stander, P de Goede, P Haredoeb
Predator Conservation Trust PO Box 90427, Windhoek, Namibia Tel: +264 (0)81 129 4060 Email:
[email protected] www.predatorconservation.com
© 2003 Predator Conservation Trust
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