Wildlife Population Dynamics in Human-Dominated Landscapes under Community-Based Conservation: The Example of Nakuru Wildlife Conservancy, Kenya

Abstract

Wildlife conservation is facing numerous and mounting challenges on private and communal lands in Africa, including in Kenya. We analyze the population dynamics of 44 common wildlife species in relation to rainfall variation in the Nakuru Wildlife Conservancy (NWC), located in the Nakuru-Naivasha region of Kenya, based on ground total counts carried out twice each year from March 1996 to May 2015. Rainfall in the region was quasi-periodic with cycle periods dependent on the rainfall component and varying from 2.8 years for the dry season to 10.9 years for the wet season. These oscillations are associated with frequent severe droughts and food scarcity for herbivores. The trends for the 44 wildlife species showed five general patterns during 1996-2015. 1) Steinbuck, bushbuck, hartebeest and greater kudu numbers declined persistently and significantly throughout 1996-2015 and thus merit the greatest conservation attention. 2) Klipspringer, mongoose, oribi, porcupine, cheetah, leopard, ostrich and Sykes monkey numbers also decreased noticeably but not significantly between 1996 and 2015. 3) Dik dik, eland, African hare, Jackal, duiker, hippo and Thomson's gazelle numbers first increased and then declined between 1996 and 2015 but only significantly for duiker and hippo. 4) Aardvark, serval cat, colobus monkey, bat-eared fox, reedbuck, hyena and baboon numbers first declined and then increased but only the increases in reedbuck and baboon numbers were significant. 5) Grant's gazelle, Grevy's zebra, lion, spring hare, Burchell's zebra, bushpig, white rhino, rock hyrax, topi, oryx, vervet monkey, guinea fowl, giraffe, and wildebeest numbers increased consistently between 1996 and 2015. The increase was significant only for rock hyrax, topi, vervet monkey, guinea fowl, giraffe and wildebeest. 6) Impala, buffalo, warthog, and waterbuck, numbers increased significantly and then seemed to level off between 1996 and 2015. The aggregate biomass of primates and carnivores increased overall whereas that of herbivores first increased from 1996 to 2006 and then levelled off thereafter. Aggregate herbivore biomass increased linearly with increasing cumulative wet season rainfall. The densities of the 30 most abundant species were either strongly positively or negatively correlated with cumulative past rainfall, most commonly with the early wet season component. The collaborative wildlife conservation and management initiatives undertaken on the mosaic of private, communal and public lands were thus associated with increase or no decrease in numbers of 32 and decrease in numbers of 12 of the 44 species. Despite the decline by some species, effective community-based conservation is central to the future of wildlife in the NWC and other rangelands of Kenya and beyond and is crucially dependent on the good will, effective engagement and collective action of local communities, working in partnerships with various organizations, which, in NWC, operated under the umbrella of the Nakuru Wildlife Forum.

Fig 1

a) A map showing the properties constituting the Nakuru Wildlife Conservancy and the neighbouring non-conservancy properties in the Naivasha-Nakuru region of Kenya (Left panel). b) A map showing the areas covered by the total counts in the Nakuru Wildlife Conservancy and the neighbouring non-conservancy properties in the Naivasha-Nakuru region of Kenya (right panel). Areas covered by the total counts are labeled with alphabetical letters.

Fig 2. a) The distribution of the total monthly rainfall across months in Nakuru Wildlife conservancy averaged over 1967 and 2011 and the standardized deviates for the b) annual, c) wet season and d) dry season rainfall components.

The vertical needles in panels b-d are the observed standardized deviates, the thick solid lines are the 4-year moving averages for the annual and wet season rainfall components and the 3-year moving average for the dry season rainfall component. The dashed horizontal lines are the percentiles of the standardized deviates for each rainfall component. The two dashed curves in the panel for the wet season rainfall are the secondary cycles with 3.5 and 2.2-year periods.

Fig 3. Trends in the density (Number /km²) of steinbuck, bushbuck, hartebeest, Greater kudu, klipspringer, mongoose, oribi, porcupine, cheetah, leopard, ostrich and Sykes monkey for the entire Nakuru Wildlife Conservancy during 1996–2015.

Fig 4. Trends in the density (Number /km²) of dik dik, eland, African hare, jackal, duiker, hippopotamus, Thomson’s gazelle, aardvark, serval cat, colobus monkey, bat-eared fox and reedbuck for the entire Nakuru Wildlife Conservancy during 1996–2015.

Fig 5. Trends in the density (Number /km²) of hyena, baboon, Grant’s gazelle, Grevy’s zebra, lion, spring hare, Burchell’s zebra, bushpig, white rhino, rock hyrax, topi and oryx for the entire Nakuru Wildlife Conservancy during 1996–2015.

Fig 6. Trends in the density (Number /km²) of vervet monkey, guinea fowl, giraffe, wildebeest, impala, buffalo, warthog and waterbuck for the entire Nakuru Wildlife Conservancy during 1996–2015.

Fig 7. Temporal trends in the aggregate biomass of the 32 herbivore species, 4 primate species and 8 carnivore species counted in the Nakuru Wildlife Conservancy from 1996 to 2015.

The species and their unit weights [39] are listed in S2 Table in the supplementary materials. The vertical needles are the biomass estimates, the thick solid line is the trend line and the band around the line is the 95% confidence band fitted by penalized cubic basis spline regression.

Fig 8. The relationship between the a) aggregate herbivore biomass versus 8-year moving average of the early wet season (March-May) rainfall, r = 0.89593, 95% CI: 0.705286–0.961465, P = 1.6734 × 10⁻⁷, n = 16 years) and b) aggregate herbivore biomass versus 8-year moving average of the wet season (March-August) rainfall, r = 0.79912, 95% CI: 0.482269–0.923621, P = 7.7404 × 10⁻⁵, n = 16 years).

The 32 herbivore species and the unit weights (in kg) used to calculate aggregate biomass are listed under herbivores in S2 Table in the supplementary materials.