An Updated Population Status of the Endemic Kafue lechwe (Kobus

G.J.B.A.H.S.,Vol.4(3):154-164
(July-September, 2015)
ISSN: 2319 – 5584
An Updated Population Status of the Endemic Kafue lechwe (Kobus leche
kafuensis) on the Kafue Flats, Zambia, for the Period 1931-2015
1
Chansa Chomba, 2Vincent Nyirenda, 3Griffin Shanungu, 3Chuma Simukonda, 4Moses Amos Nyirenda &
3
Chaka Kaumba
1
School of Agriculture and Natural Resources, Disaster Management Training Centre, Mulungushi University,
P. O. Box 80415, Kabwe, Zambia.
2
Copperbelt University, Kitwe, Zambia. Corresponding Author: Chansa Chomba
3
Zambia Wildlife Authority, Chilanga, Zambia
4
World Wide Fund for Nature, Zambia Country Office, Lusaka, Zambia
Abstract
Kafue lechwe (Kobus leche kafuensis, is and endemic sub-species of semi aquatic antelope that has been counted by
aerial survey since 1931. The 2015 survey counted lechwe and other large herbivores including cattle and covered an
area approximately 6, 035 km2 in extent, encompassing Blue lagoon and Lochinvar National Parks and Kafue flats Game
Management Area. Historic data on population size and trophy hunting were collated and analyzed. Results showed that
the population estimate in 2015 was 28,660 which was equivalent to 89% decline from the 1931 estimate of 250,000
individuals. This implies that only 11 % of the 1931 population estimate has remained, giving an annual loss of 2,464 or
7 lechwes/day of which only one lechwe was attributed to legal hunting and the remaining six to poaching an other
factors. The number of cattle had increased by more than 300% from an upper limit of 18,841 in 2005 to 92,242
individuals in 2015, representing a metabolic equivalent of 272,726 lechwe. It was concluded that lechwe was facing a
precipitous population decline depicting failure to regulate in terms of population dynamics. Cattle were on the other
hand experiencing an almost perfect exponential growth which is likely to out-compete lechwe on the Kafue Flats.
Further research is required to assess the impact of increasing cattle populations and increasing human encroachment on
lechwe habitat.
Keywords: Kafue lechwe, estimate, Kafue flats, population decline, cattle, metabolic equivalent
1. Introduction
The Kafue lechwe (Kobus leche kafuensis Haltenorth 1963) is a gregarious antelope (Figure 1) and endemic
subspecies restricted to the Kafue flats. The Kafue River passes through the flats almost cutting it into two equal halves
named Kafue Flats north and south banks. The Lochinvar National Park is located in the south bank and Blue Lagoon in
the north but the Kafue Flats Game Management Area (GMA) covers both banks. The earliest effort to estimate lechwe
population was by Pitman (1934) who estimated the population size of approximately 250,000 individuals in 1931. This
number has since continued to decline over the last 84 years to about 28,660 in 2015 suggesting a significant decline of
89% or an annual decline of 1.05%. The present effort to estimate the population size was carried out as part of the longterm population monitoring and to update the population estimate last done in 2005 when it was estimated to be 38,448
(Chansa and Kampamba, 2009). Growth in the numbers of this endemic subspecies is exclusively through natality and
not immigration. It is therefore critical to monitor population performance and identify key environmental parameters
responsible for the decrease or increase in population size. Major concerns have been raised concerning pastoralism
which has led to sudden increase of cattle keeping communities taking advantage of the rich pasture on the flats.
Artisanal fishing is also permitted and has led to unplanned and often unregulated fishing camps along the entire river
length of the Kafue flats. Such multiple land use systems require monitoring particularly of the endemic Kafue lechwe,
which is more vulnerable to increasing human settlements and associated activities.
Figure 1 Kafue Flats lechwe (Kobus leche kafuensis), a gregarious semi-aquatic antelope endemic to the Kafue Flats,
April 2015, Zambia
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2. Materials and Methods
2.1 The Study Area
The Kafue flats is approximately 6,035 km2; comprising 860 km2 or 17 %, (combined area for Lochinvar 410 km2
and Blue Lagoon 450 km2) and 5,175km2 (83 %) of the Kafue Flats GMA (Figure 2).
2.2 General Methodology and Sampling Techniques
Data collection in this study involved two approaches; i) an intensive desk review of all the population data
collected from previous surveys from 1931 to 2015, and ii) intensive review and critique of 2015 survey carried out by
the Zambia Wildlife Authority (ZAWA) the institution mandated by law to manage all wildlife and Protected Areas in
Zambia.
Like in the previous surveys, the 2015 survey also used an aerial stratified random sampling technique using a fixed
high wing Cessna 206 aircraft, a method consistent with the previous surveys. The technique used in this survey is
similar to the one described by Bell et al. (1973) for lechwe census, subsequently improved and used by Howard, Jeffery
and Grimsdell (1984) when estimating black lechwe population of the Bangweulu Swamps in 1983. The 2015 survey
was further improved by the front seat observer recording animal sightings into Arc-pad on a hand held computer. In the
2005 survey, observers wrote animal sightings on each side of the plane on a note book and later entered into a desk top
computer at the base camp. In both surveys however, Global Positioning System (GPS) was used and the Geographical
Information System (GIS) was used in mapping the spatial distribution of animals.
Observations were also made for cattle and fishing camps, as these also had an impact on the habitat quality and
lechwe population in general. Data on trophy and meat hunting for the period 2006 – 2014 were also collected from
ZAWA licencing office as this is also a form of mortality which may have a negative impact on lechwe population
increase.
Figure 2 Location of Kafue Flats, habitat for the endemic Kafue lechwe (Kobus leche kafuensis), Zambia
2.3 Stratification
The GPS coordinates of areas of occurrence of lechwe herds were taken and used to identify and draw boundaries
of density strata. The study area was then divided into strata (Figure 3) classified as low, medium and high. Stratification
served to reduce the variances of the total area when the individual strata are combined. North - South bearing transects
were flown in each population density stratum in the north and south banks of the Kafue River (Figure 2).
2.4 Sampling intensity
The 2015 utilized a sampling intensity ranging from 11 - 21% (Figure 3), giving a greater opportunity of
maximizing searching effort, area coverage and reliability of data collected.
2.5 Aircraft, Survey Crew and Equipment Used
A Cessna 206 fixed high wing aircraft was used (Figure 4). The aircraft was fitted with a Radar Altimeter. The
survey crew consisted of five people; one pilot, one navigator, two observers, and one GIS specialist/data recorder. Two
observers counted animals within the swathes one on each side of the aircraft. The two observers were considered to be
mutually dependent and observations were treated as coming from a single transect. Transects were flown from the edge
of the woodland to the riverbank and vice versa in the north and south banks of the Kafue River (Figure 3).
2.6 Flight Procedure and Recording of Sightings
The location of coordinates for all transects were entered into a GPS each day before taking off from the base and
used for navigation when flying. The transects were flown at an average speed of 150 km/hour and at a nominal
(theoretical) height of 61m a.g.l. While flying along the transects, observers kept their heads in a constant position with
reference to a masking tape marking on the window to avoid parallax error. Observers recorded the species and number
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of animals seen and were reminded every two minutes to block the counts to facilitate plotting of animal densities. All
Method
lechwe, sighted between the streamers were counted and recorded.
• Aerial Stratified Random Sampling Approach – similar to previous surveys – with modifications.
• Firstly flew a reconnaissance flight to determine the areas with the highest densities of mammal and birds
S.I=20%
species.
S.I = 11%
• After the flight, the area was stratified.
S.I=15%
• A survey plan made with different sampling intensities per strata.
• Strata with highS.I
densities
= 10% – transect spacing was limited to 2km – these areas comprised the National Parks
and the floodplain expanse between the two parks.
• Strata with low density – transect spacing was limited to 4km –S.I=14%
these areas mostly comprised the GMA and
areas with very low mammal desnsity.
S.I=21%
Figure 3 Sampling intensity of the Lechwe habitat, Kafue Flats, 2015, Zambia
Figure 4 Fixed high wing aircraft with wing struts for attaching streamers suitable for aerial surveys, Kafue Flats,
Zambia.
2.7 Data Analysis
As in the previous surveys, particularly the 2005 survey, population estimates, animal densities, and other statistics
were calculated using a special software package for wetland areas as described by Bell et al. (1973) which is based on
Jolly’s (1969) and the parameters were calculated as follows:
Y (i) = ΣNiYi
Where;
Ni = the total number of units in the i th stratum,
Y(i) = the estimate of the population size,
Yi = the average number of animals per unit over the number of units sampled per stratum.
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The standard error of Y(i) = √variance (Y (i) )
Where;
Variance (Y (i) ) = ΣNi (Ni – ni )
n
Weighted variance Syi 2= 1 {Σy2i - (Σ yi) 2}
ni
The average rate of decrease for the intervening period 1931 – 2015 was calculated based on the formula;
Nt = Noert
Where r is the exponential rate of increase or decrease, and e is the base of natural logarithm taking the value 2.7182817
and t is the time between the censuses. The exponential rate of increase being calculated as; r = ln (Nt/No)
2.8 Cattle - Lechwe Metabolic Ratios
The comparison of cattle and lechwe metabolic ratios were based on Kleiber's law, Holling’s disk equation and
Marginal Value Theorem. Kleiber’s law states that the metabolic rate (q0) of an animal is the mass of the animal (M)
raised to the 3/4 power: q0 = M3/4 (or raised to 0.75). Therefore, the mass of the animal increases at a faster rate than the
metabolic rate. Kleiber's law explains the relationship between the size of the animal and the feeding strategy it uses. If
the food eaten is reasonably the same, such as cattle and lechwe the ratio of their metabolic weight gives the exchange
ratios between the two species. In order to get the metabolic size of cattle and lechwe, the weight of one cow was
assumed to be equivalent to one animal unit (450 kg), and the weight of lechwe was obtained from literature as being
about 118 kg (Skinner and Smithers ,1990 ). Weight in kilogrammes was raised to the power of 0.75 or ¾ (Kg 0.75). It is
on this basis that we calculated the metabolic equivalents.
3. Results
3.1 Population Estimates
The population estimates from previous surveys 1931 – 2015 showed a precipitous populating decline of 89% from
the 1931 estimate of 250,000 (Table 1).
The first significant decline was recorded after the construction of the Itezhi-Tezhi dam in 1979 after which only an
average of 20% of the 1931 estimate survived. This decline has continued to date (Figure 4 a & b). By the 1970s, the
population had stabilized around 100,000. Soon after commissioning the Itezhi – Tezhi Hydroelectricity dam, the
population declined to about 50, 000 until 1994 and to 40,000 by 1995. The downward trend continued to about 38,000
in 2005, declining further by almost 10,000 individuals to 28,660 in 2015. The population’s overall mean of 68,714
individuals was however surpassed in 1984 (Table 1). The regression equation shown in Figure 4b gives a slope of b = –
2, 2464.2, which implies a net loss of (–2, 464.2 individuals each year or seven individuals on a daily basis (–2,
464.2/365 = 7 individuals) giving an annual decline of 1.05%.
Year
1931
1970
1971
1972
1973
1975
1981
1982
1983
1987
1988
1989
1990
1991
1993
1994
1995
1998
1999
2002
2005
2015
Table 1 Kafue lechwe population trend analysis for the period 1931 to 2015, Kafue flats, Zambia
Population Source
Expected
Difference
Percentage (%)
estimate
Overall mean
between
remaining of the
(before and after
estimate &
1931 estimate
the dam)
overall mean
Pitman, 1934
68,714
250,000
94,075
Bell et al. 1973
68,714
25,361
38.00
93,215
Bell, et al. 1973
68,714
24,501
37.28
93,158
Bell et al. 1973
68,714
24,444
37.26
109,612*
Osborne et al. 1973
68,714
40,898*
43.84*
80,774
Osborne et al. 1975
68,714
12,060
32.30
45,867
Howard et al. 1983
68,714
-22,847
18.34
41,345
Howard, et al. 1983
68,714
-27,369
16.00
41,155
Howard et al. 1983
68,714
-27,559
16.00
50,715
Howard, et al. 1987
68,714
-17,999
20.28
65,018
Howard, et al. 1988
68,714
-3,696
26.00
47,145
Jeffrey, et al. 1988
68,714
-21,569
18.85
44,538
Jeffrey, et al. 1990
68,714
-24,176
17.81
68,872
Jeffrey, et al. 1991
68,714
158*
27.54
64,940
Kapungwe, 1993
68,714
-3,774
25.97
50,000
Jeffrey, 1994
68,714
-18,714
20.00
40,000
Tembo, 1995
68,714
-28,714
16.00
37,120
Kampamba, et al. 1998
68,714
-31,594
14.84
45,000
Kampamba, et al. 1999 68,714
-23,714
18.00
42,000
Kampamba, et al. 2002
68,714
-26,714
16.00
38,448
Chansa & Kampamba
68,714
-30,266
15.00
28,660
Shanungu & Kaumba
68,714
-40,054
11
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300,000
200,000
38,448
2005
28,660
42,000
2002
37,120
1998
45,000
40,000
1995
64,940
1993
50,000
68,872
44,538
1990
1991
47,145
1989
41,155
1983
65,018
41,345
1982
50,715
45,867
1981
93,158
1972
80,774
93,215
1971
50,000
1975
94,075
100,000
109,612
150,000
1970
Population Estimate
250,000
250,000
2015
1999
1994
1988
1987
1973
1931
0
Years
(a)
300,000
250,000
Populatiion estimate
200,000
150,000
100,000
y = -2464.2x + 5E+06
R2 = 0.8024
50,000
2020
2010
2000
1990
1980
1970
1960
1950
1940
1930
1920
0
-50,000
Ye ars
(b)
Figure 4 a) Comparison of lechwe population estimates before construction of the Itezhi -Tezhi Hydroelectricity dam
1931-1979, and after commissioning the dam 1980 - 2015, b) population trends for the period 1931 – 2015. Arrow in a
and b shows the 2015 population estimate which is the lowest since 1931.
3.1.1 Comparison of the Population before and After Dam Construction
The first significant decline is recorded after the construction of the Itezhi-Tezhi dam in 1979 after which only an
average of 20% of the 1931 estimate survived. Mann Whitney U test showed a significant difference between the lechwe
population estimates before and after the construction of the dam (U 0.05 (2) 6, 15 = 71, P < 0.001, see Table 2.
This comparison of population estimates before 1979 and after the construction of the Itezhi-Tezhi dam disrupted the
flooding regime and resulted into a significant difference in the lechwe population (Table 2). By the 1970s, the
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population had stabilized around 100,000. Soon after commissioning the Itezhi – Tezhi dam the population declined to
about 50, 000 until 1994 and to 40,000 by 1995, which is below the carrying capacity K of 100,000. The downtrend has
continued to about 38,000 recorded in this study. The population’s overall mean of 68,714 individuals was however
surpassed in 1984. This down ward trend has continued to date.
Table 2 The Mann-Whitney U Test for Comparison of Kafue lechwe numbers estimated before and after the Itezhitezhi
dam, Kafue flats, Zambia
Population estimates before dam construction
Population estimates after dam construction
Year
Population estimate
Rank
Year
Population estimate
Rank
1931
250,000
1
1981
45,867
13
1970
94,075
3
1982
41,345
17
1971
93,215
4
1983
41,155
18
1972
93,158
5
1987
50,715
10
1973
109,612
2
1988
65,018
8
1975
80,774
6
1989
47,145
12
R1 = 21
1990
44,538
15
Mean = 120,139
n1= 6
1991
68,872
7
1993
64,940
9
1994
50,000
11
1995
40,000
19
1998
37,120
21
1999
45,000
14
2002
42,000
16
2005
38,448
20
R2 = 210
n2 = 15
Mean = 48,144
U 0.05 (2) 6, 15 = 71, P < 0.001
Discussion –
3.2 Distribution
The 2015 end of rainy season distribution as was skewed towards mainly the North bank and secondly around Blue
Lagoon and Lochinvar National Parks on higher grounds as the floods had not yet receded (Figure 5). This in a way,
tended to avoid areas with heavy human encroachment in form of fishing camps and cattle grazing areas as shown in
Figure 6.
Map of distribution and popula
•
•
•
Figure 5 Distribution of lechwe in April 2015, Kafue Flats, Zambia.
3.3 Number of Lechwe Hunted
The mean number of lechwe hunted for the period 2006 – 2014 was 432 for resident hunters and only 35 for non
resident /Safari (Table 3). A combination of the two off-take quotas had a collective loss of only one lechwe/day for
which resident hunting was responsible for 93% of the daily single loss. Thus given 7 losses of lechwe per /day, (based
on slope of b = (–2, 2464.2/365 = 7 individuals), legal hunting only took away one lechwe per/day and the other six were
attributed to poaching (Figure 6) and other factors.
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Table 3 Number of lechwe hunted under resident and nonresident/safari for the period 2006- 2014, Kafue Flats, Zambia.
Year
Hunting quota
Total
Resident
Non Resident (Safari)
2006
580
31
611
2007
484
61
545
2008
605
52
657
2009
879
29
908
2010
217
28
245
2011
644
49
693
2012
482
44
526
2013
0
6
6
2014
0
12
12
Total
3,891
312
4,203
Mean
432
35
467
Daily loss (/365)
1.18
0.09
1.27
(Source: Zambia Wildlife Authority Licencing Office, 2015).
Increase capacity of KFAMU to curb poaching
Figure 6 Poached lechwe on the Kafue Flats, Zambia (Poaching is one of the major causal factors for the precipitous
•decline
Poaching
of lechwe
is a daily occurance – all year round.
of lechwe
population).
Blue lagoon and lochinvar almost neglected – vehicles and others low.
Reduction
Lechwe
Range
•3.4Often
huntersofuse
motorbikes
to chase down lechwes and shoot.
The Kafue lechwe foraging range has declined, being restricted to areas close to and between Lochinvar and Blue
Lagoon National Parks (Figure 7). The north bank, mainly the area between Blue lagoon and the Kafue river eastwards
•towards
On average,
a hunter
can Plantation
kill up to 10islechwes.
the Kafue
Sugar
currently where most of the lechwe are concentrated, and inevitably the most
important lechwe range as it also the area with minimal human disturbance (Figure 7c) a factor also recorded in 2005
•survey
Due to
of effective
patrols on (2005;
the flats2009).
– manyThis
offenders
go
bylack
Chansa
& Kampamba
observation
represents a significant reduction in the distribution
range
for Kafue
lechwe recorded
by Howard
undeterred
– especially
on the North
bank. et al. (1984), at which time the lechwe covered the whole area shown in
Figure 2 above. As shown in Figure 7 a & b lechwe habitat has been encroached by human settlements and consequently
to poaching
Figure
6). Lechwe annually from
•exposed
We could
be losing (see
as many
as 2000
Settlement, villages and fishing camps
poaching!
(a)
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(b)
Extending o
boundaries
the still pres
for the lech
waterbirds.
The Creatio
Lechwe Nat
(c)
Figure 7 a, b) Human settlements, fishing camps and cattle grazing areas, c) proposed new boundaries to join Blue
Lagoon and Lochinvar National Park, to enclose and secure key lechwe habitat which is also relatively free from human
encroachment, Kafue Flats, April 2015.
3.4.1 Cattle Populations
In 2005 an upper limit of the cattle population was 18,841 with a metabolic equivalent of 56, 523 lechwe, that
outnumbered the lechwe population of 38, 448 individuals. In 2015 the herds of cattle had increased by more than 300%
to 92,242 cattle, giving a metabolic equivalent of 276, 726 lechwe which by far outstripped the lechwe population
estimated at 28,660 individuals (Figure 7). Cattle populations had exponentially increased while the lechwe population
declined.
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276,726
300,000
250,000
200,000
150,000
92,242
56,523
38,448
50,000
18,841
28,660
100,000
0
Lechwe population
Cattle population
Cattle metabolic equivalent of
lechwe
2005
38,448
18,841
56,523
2015
28,660
92,242
276,726
2005
2015
Figure 8 A comparisons of cattle and lechwe estimated population and their metabolic biomass equivalents, Kafue Flats,
Zambia
4. Discussion
4.1 Population Status
The lechwe population has declined by 89% over the intervening interval 1931-2015 driven by two major reasons;
disruption of the flooding regime after the commissioning of the Itezhi-Tezhi dam in 1979, and poaching together with
habitat encroachment by humans and several other associated human activities. Pitman (1934) estimated 250,000 in 1931
and Bell et al. (1973) estimated a total of 93,000-95,000 in the early 1970s, both estimates being carried out before the
construction of the Itezhi-Tezhi dam. The decline became more significant after the construction of the Itezhi-Tezhi dam
in 1979, after which the population declined significantly from about 93,000 to 45,000, representing a 50% loss from the
pre dam population estimates. The major causes for such drastic decline still remain debatable, though Sayer and van
Lavieren (1975); Schuster (1976, 1977, 1980) and Rees (1978a) argued that the alteration of the flooding regime could
disrupt the lechwe breeding behaviour and social organization. We agree with this assertion, since lechwe depends on
floods for the lek system, a reproductive behaviour developed over a very long period of time. Sayer and van Lavieren
(1975) further predicted that the area flooded will be reduced thereby reducing the carrying capacity and a large
reduction of the size of the population of lechwe was expected as a result of the construction of the dam. This prediction
was also correct as the current results show a sharp decline after 1980. According to Rees (1978a, 1978b) the future of
lechwe population was bleak because the Itezhi-Tezhi dam would reduce the flood regime affecting plants and modifying
herbage available to the lechwe. Kapungwe’s (1993) standpoint was that the altered flooding regime did not contribute
significantly to the population decline; he attributed the decline to poaching alone. Despite this view, the lechwe
population decline was sharp after the commissioning of the dam in 1979 (Figure 4a; Table 1 & 2) changing from 80,774
in 1975 to 45, 867 in 1981 representing a loss of approximately greater 44%. While poaching may have played a
significant role, the impact of the construction of the Itezhi-Tezhi dam, which disrupted the natural flooding regime,
appear to have been at this time one of the major factors responsible for the lechwe population decline. Although further
study is required to identify additional factors contributing to the decline and enhance this argument, we still suggest that
the decline of the lechwe is attributed to a combination of factors, in which the impact of the dam and poaching are the
major ones. We also still argue that the lechwe population estimates of 68,872 in 1991 and 64, 940 in 1993 were over
estimates. This is because it would not be possible to have an increase of 24,000 individuals in a single year in an area
where poaching is the main factor in population decline as noted and acknowledged by Kapungwe (1993). The increase
of 24,000 per single year cannot be explained and hence discounted. It is also difficult to explain the loss of 15,000
individuals in a single year between 1993 and 1994 as reflected in Table 1. Kampamba et al. (1998) noted a further
decline from the 1980s to the 1990s during which time the population fluctuated between 40,000 - 45, 000. This further
confirms that the estimates for 1991and 1993 are likely to have been over estimates. It is in this line of thought that the
2005 estimate of 38, 448 and the 2015 lower estimate of 28, 660 confirm this population decline. Reasons given by
Shanungu and Chaka (2015) of Mimosa pigra as one of the major factors in the current population decline is here by
discounted because, while the invasive alien species poses a major threat for the future, the current area covered by
Mimosa pigra is outside the key lechwe distribution and foraging range which according to the 2005 and 2015 survey is
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in the north bank. This argument to discount the impact of Mimosa pigra does not in any way suggest that the alien
species should not be eliminated, but rather to discount it for now as one of the major causal factors for the 89% decline
in lechwe population.
What is critical at the moment is to know the rate of decline and establishes the time available in which to take
remedial steps. In this case, remedial measures based on the regression analysis were supposed to have started in 1984
(Figure 4a & b). The greater the rate the more urgent the task to determine what caused it. Declines detected while a
species is relatively abundant may be easier to rectify than waiting until the species is no longer abundant. The
population performance shown in Figure 4b shows an extreme case of failure to regulate. Based on the population models
provided by Sinclair & Grimsdell (1982) (Figure 7) the lechwe shows an extreme case of failure to regulate so that K
itself is reduced and eventually the population plunges to extinction. This should inevitably necessitate the review the of
carrying capacity of the Kafue flats as it appears that the estimated population’s carrying capacity of 100,000 might have
declined over time due to among other factors increased human encroachment, expansion of the invasive alien weed,
Mimosa pigra, which is now estimated to cover 29 km 2 (this was reduced through mechanical control) and bush
encroachment on the former open plains due to disrupted flooding a regime (Thomas, 2005), increased herds of cattle and
many more.
Since 1994 the population declined to figures below 50,000. The later decline from 40,000 and below is attributed
to high levels of poaching recorded during and after the period of transformation of the Department of National Parks and
Wildlife Service (NPWS) to a semi autonomous statutory body Zambia Wildlife Authority (ZAWA). This period had a
severe impact on the lechwe population, due to staff retrenchment and reduced funding for field operations. Reduced law
enforcement operations on the Kafue flats accentuated illegal human settlements, which also increased poaching levels
and loss of lechwe habitat (see Figure 7a&b). For this reason, the protection of wildlife should be improved and
strengthened substantially and levels of harvesting (trophy and resident hunting) should be based on the successes of this
protection.
The observed disparity between the south and north banks has accentuated. Kapungwe (1993) estimated that in
1993, the north bank had 55% and south bank 45 % of the total lechwe population estimate. In 2005 survey the difference
between north and south banks had increased to 84% and 16% for the north and south banks respectively. The
explanation for the low numbers in the south bank (16% of total) are attributed to a number of reasons some of which
are; the increased levels of human settlements in the south bank which has reduced the habitat available for the lechwe,
the expanding invasive alien weed Mimosa pigra that was estimated at 29 km2 which had displaced lechwe from its
traditional feeding areas around Chunga lagoon into the GMA near fishing camps and hence exposing the species to
increased poaching, high livestock densities, wildfires which destroy permanent wetland vegetation during the dry
season and other human activities in the south bank have exacerbated the decline. It was on this basis that even in the
2015 survey report, the earlier suggestion to adjust park boundaries as shown in Figure 7c was sustanaied.
Figure 7 Models of population regulation: (a) shows almost perfect regulation to the equilibrium level with only minor
fluctuations about k; (b) shows less accurate regulation at first but gradually the equilibrium level is reached and then
maintained; (c) shows that perfect regulation is never achieved; instead the population shows a constant cycle of change,
oscillating with k in a regular way. (This is called a stable limit cycle); and; (d) shows an extreme case of failure to
regulate; the population overshoots k so much that k itself is reduced and eventually the population plunges itself to
extinction. (Sinclair and Grimsdell, 1982).
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(July-September, 2015)
ISSN: 2319 – 5584
2.8 Cattle - Lechwe Metabolic Ratios
In 2005, the cattle population was estimated at 15,650 ± 3,191. In 2015 this estimate had increased to 92,942.
Viewed from this angle, the cattle population would represent a competitive factor in the lechwe range that cannot be
ignored. As livestock numbers increase over time, the lechwe is likely to continue losing its range to cattle. Intensive
surveys of cattle as well as to make it possible to calculate the people/cattle ratio or rate of increase for cattle as was
done for the Barotse flood plain (van Gils, 1988) would be needed sooner than later. Systematic collection of data on
cattle will be necessary in future surveys in order to establish the sustainability of grassland productivity under increased
cattle numbers and its impact on wildlife. There is need to build up a more consistent picture of the cattle population
estimates. This is important because the lechwe and cattle interactions are critical in determining their impact on the
range and nutrient recycling.
Acknowledgement
The ZAWA staff that carried out the 2015 survey is herby thanked for the job well done. World Wide Fund for
Nature (WWF) Zambia Country Office provided financial support for the survey. Chaka Kaumba other than being a co
author was helpful in his providing the GIS support. Mr. Shanungu brought his longtime experience from the control of
Mimosa pigra, a project he had supervised with enthusiasm. Ground crew drivers and other support staff are also
acknowledged. Pilots are never forgotten in this noble task, as they display excellent skills in maintaining transect lines
even during turbulent weather.
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