Population estimate for geladas ( Theropithecus gelada) living in and around the Simien Mountains National Park, Ethiopia

Abstract

Geladas (Theropithecus gelada), endemic to Ethiopia, are listed as rare by the IUCN and have an Appendix II listing in CITES. The highest density of geladas, and the only place where they are officially protected, is found in the Simien Mountains National Park (SMNP). However, to date, no comprehensive census of geladas in the area has been carried out. Here, we use a direct count to census geladas living in and around the SMNP. We also examine the age and sex structure of the gelada groups surveyed. A total of 4264 geladas were counted in the area. From these results, we estimate that approximately 2460 geladas live within the current boundary of the SMNP. With respect to age-sex categories, we counted approximately 3 adult females to each adult male, and when bachelor groups were excluded, there were 4.2 females per adult male. The ratio of immatures and subadults to adults was 1.2 immatures per 1.0 adult. The actual size of the SMNP gelada population is significantly lower than expected from previous unpublished estimates. However, gelada populations appear to be healthy in the SMNP, despite a high amount of competition with grazing livestock.