Masai giraffe population change over 40 years in Arusha National Park

A population of Masai giraffes (Giraffa camelopardalis tippelskirchi) occurs in Arusha National Park (ANP), which is not part of the regular Tanzanian national wildlife monitoring scheme. Urban development of Arusha city and agricultural expansion have contributed to the increasing isolation of ANP from other protected areas in northern Tanzania. The only published data on the Masai giraffe population of ANP were individual-based data collected in 1979 and 1980. Here, we used individual-based data from 2021 to 2022 to provide an update on the current population size, population sex and age structure, movements, and genetic connectivity of giraffes in ANP. We documented a 49% population decline and changes in the age distribution, adult sex ratio, reproductive rate, and movement patterns relative to the previous study. Mitochondrial DNA analysis revealed genetic connectivity between ANP and other populations east of the Gregory Rift Escarpments in northern Tanzania and south-eastern Kenya, evidence that the Masai giraffe once moved widely across the landscape.