Wildlife populations are declining severely in many protected areas and unprotected pastoral areas of Africa.
Rapid large-scale land use changes, poaching, climate change, rising population pressures, governance, policy, economic
and socio-cultural transformations and competition with livestock all contribute to the declines in abundance. Here we
analyze the population dynamics of 15 wildlife and four livestock species monitored using aerial surveys from 1977 to
2011 within Kajiado County of Kenya, with a rapidly expanding human population, settlements, cultivation and other
developments. The abundance of the 14 most common wildlife species declined by 67% on average (2% / yr) between
1977 and 2011 in both Eastern (Amboseli Ecosystem) and Western Kajiado. The species that declined the most were
buffalo, impala, wildebeest, waterbuck, oryx, hartebeest, Thomson’s gazelle and gerenuk in Eastern Kajiado (70% to
88%) and oryx, hartebeest, impala, buffalo, waterbuck, giraffe, eland and gerenuk in Western Kajiado (77% to 99%).
Only elephant (115%) and ostrich (216%) numbers increased contemporaneously in Eastern and Western Kajiado,
respectively. Cattle and donkey numbers also decreased on average by 78% in Eastern Kajiado and by 37% in Western
Kajiado. Sheep and goats decreased the least in Eastern (28%) but increased in Western (96%) Kajiadio. Livestock
dominated (70-80%) the total large herbivore biomass throughout the 1977-2011 monitoring period. The distribution of
wildlife contracted dramatically during 1977-2011, most especially for wildebeest, giraffe and impala. Only zebra and
ostrich distributions expanded in the county. However, livestock distribution expanded to densely cover most of the
county. Our findings point to recurrent droughts, intensifying human population pressures, land use changes and other
anthropogenic impacts, decades of ineffective or failed government policies, legislations, law enforcement, management
institutions and strategies as the salient causes of the declines and range compressions. We recommend several urgent
measures to rehabilitate the depleted wildlife populations and habitat richness, restore their ecological resilience to
droughts and secure pastoral livelihoods.