Habitat Heterogeneity and Seasonal Dynamics of Primate Populations in Nech Sar National Park, Ethiopia

ABSTRACT

Primate populations in East Africa are increasingly affected by habitat fragmentation and seasonal resource variability. This study assessed species‐specific density, abundance, population structure and habitat use of three primate species—the Olive Baboon ( Papio anubis ), Mantled Guereza ( Colobus guereza ) and Vervet Monkey ( Chlorocebus pygerythrus )—in Nech Sar National Park (NSNP), Ethiopia, across dry and wet seasons. Using distance sampling, we estimated species‐level densities and encounter rates rather than relying solely on raw counts. A total of 503 individuals were recorded, with higher observed abundance in the wet season (268) compared to the dry season (235). Density estimates were consistently higher in the wet season for all species, with P. anubis reaching up to 21.9 individuals km ⁻² , followed by C. pygerythrus (8.5 individuals km ⁻² ) and C. guereza (7.4 individuals km ⁻² ). Seasonal variation in encounter rates was statistically significant ( t  = −7.201, df  = 2, p  = 0.019). Because density estimates were derived using distance sampling, these seasonal differences are interpreted primarily as reflecting variation in detection probability and spatial aggregation of primate groups rather than definitive changes in true population size. Riverine forests (Arba Minch Groundwater Forest) supported the highest density and species co‐occurrence, whereas open grassland habitats were dominated primarily by P. anubis . Species‐level habitat associations showed that C. guereza was strongly restricted to riverine forests, while P. anubis utilized all habitat types, indicating higher ecological flexibility. Beta diversity analyses revealed moderate spatial turnover ( β ≈0.42) between riverine and woodland habitats, highlighting the importance of habitat heterogeneity. Demographic analyses indicated female‐biased sex ratios and relatively higher juvenile proportions during the wet season. However, because the study covered only a 6‐month period, these demographic patterns should be regarded as preliminary and may also reflect seasonal differences in detectability among age and sex classes. Overall, the results demonstrate that habitat heterogeneity and seasonal resource dynamics primarily influence primate distribution and detectability rather than absolute population size. These findings highlight the ecological importance of riverine forests and the need to conserve habitat mosaics to sustain primate populations under increasing anthropogenic and climatic pressures.