What factors drive ungulate dynamics in Laikipia District?
Nicholas J.
1
Georgiadis ,
J. G. Nasser
1
Olwero ,
and Gordon
2
Ojwang’
1. Mpala Research Centre, 2. Department of Resource Surveys and Remote Sensing
RESULTS
RATIONALE
Conservation strategy in Africa has broadened in scope from an initial focus on protectionism to the inclusion of
human-occupied landscapes.
Conserving large mammals in non-protected areas will depend partly on
management intervention that is better informed about wildlife dynamics in livestock-dominated landscapes.
We define and interpret the dynamics over the last 21 years of wild ungulates that share the landscape with
livestock in Laikipia District, a non-protected savanna in central Kenya. The factors examined that could potentially
influence ungulate dynamics were land use, rainfall-dependence, density-dependence, and trends over time.
1. A summary of coefficients associated with variation in the biomass density of each species (Table 1) showed land use to
greatly influence herbivore abundance. Wild herbivores were diverse and abundant on pro-wildlife properties (mean of 1.7
t.km-2), despite sharing the landscape with a slightly higher biomass density of livestock (mean of 2.7 t.km-2). Densities
and diversities of wild species were lower on wetter transitional properties (mean of 0.64 t.km-2), and much lower on drier
group ranches (mean of 0.10 t.km-2). Mean biomass densities of livestock on transitional and group ranches were
respectively 7 and 23 times greater than wildlife densities.
2. Only the numerically dominant wild grazers and browsers showed evidence of density-dependence (zebra and giraffe).
Four wild species exhibited rainfall-dependence (zebra, giraffe, Thomson’s gazelle and hartebeest), the latter three only in
the first half of the time series. Cattle were only weakly rainfall-dependent because this is not a closed system for livestock
(for example, livestock enter or leave the District during droughts).
THE APPROACH
The data comprised 13 sample surveys of the entirety of Laikipia District conducted by the Department of Resource
Surveys and Remote Sensing between 1985 and 2005, the latter half in collaboration with Mpala Research Centre.
Variation in the biomass density of 9 wild and two domestic species was compared among three contrasting landuse types (Fig. 1): commercial ranches that favor wildlife (‘pro-wildlife ranches’), communal ‘group ranches’ largely
practicing pastoralism, and the remainder (‘transitional’ properties) using linear model selection. The influence of
rainfall on ungulate dynamics was tested using a cumulative index of monthly rainfall deficit or surplus between
successive surveys (Fig. 2).
3. All but two wild species (zebra and Grant’s gazelle) showed declining trends on at least one land-use type (Fig. 3).
Declines were especially steep on pro-wildlife properties over the latter half of the series.
Fig. 3. Biomass density time series and
model fits for wildlife and livestock species
in Laikipia District between 1985-2005, on
three land-use types: pro-wildlife (open
circles, solid line), transitional (black
circles, dotted line) and group ranches
(grey circles, dashed line).
Fig. 1.
Distribution and relative
abundance of livestock and wildlife
in Laikipia District, February 2005,
with 3 land-use types featured: prowildlife (white), group ranch (light
grey), and transitional (dark grey).
Apparent absence of herbivores
signifies that none were observed
within transects, not necessarily
actual absence.
Fig. 2. Mean annual rainfall over 40
years from 5 gauging stations scattered
across the study area (bold black line,
with standard errors).
The 5-year
moving average (dotted line) and longterm mean (639 mm; dashed line) are
also given.
Annual Rainfall (mm).
Table 1. Coefficients (with probability
values in parenthesis) associated with
model parameters remaining after model
selection.
1200
1000
800
600
400
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0
1965
SYNTHESIS AND APPLICATIONS
1970
1975
1980
1985
1990
1995
2000
2005
Years
Mpala Wildlife Foundation, the African Wildlife Foundation, and the Kenya Wildlife Service supported sample
surveys. We acknowledge the dedication and expertise of the survey crews at DRSRS. M. Stanton, J.
Goheen, M. Norton-Griffiths, R. Sensenig and R. Pringle gave helpful advice. Thanks to G. Grant, C.
Mortensen, C. Burt, R. Vigne and J. Evans for rainfall data.
1. Well-supported insights into the dynamics of savanna herbivores affirmed the sufficiency of sample counting for
most conservation and monitoring purposes in non-protected landscapes.
2. Where wildlife is not favored, a resilient few species (gazelles and plains zebra) can persist with high densities of
livestock. Maintaining higher wild species diversity on communal properties will depend on the creation of
conservancies from which livestock are, in effect, excluded, and which are sufficiently large and connected to
prevent repeated local extinction and restoration. Such conservancies are expected to endure only if benefits from
wildlife to community members exceed opportunity costs.