Distribution and habitat of grivet monkeys (Cercopithecus aethiops aethiops) in eastern and central Eritrea

A 5‐month survey was conducted in Eritrea with the aim of collecting information on the distribution and habitats of primate species, including grivet monkeys (Cercopithecus aethiops aethiops). The survey area covered more than 22 000 km² (N 14°17′?16°19′, E 37°13′?39°53′). Grivet monkey habitats were described by altitude, precipitation, normalized difference vegetation index (NDVI), vegetation classes and distances to nearest settlements and rivers. We detected grivet monkeys at 44 sites, making Eritrea probably the northern most range of the current grivet monkey distribution. Average group size was 9.1. Grivet monkeys were, at different sites, sympatric with either hamadryas (Papio hamadryas hamadryas) or olive (P. h. anubis) baboons. Grivet ‘home‐ranges’ had a NDVI significantly higher than the average of the area of survey (AoS), and the proportion of wooded and forested areas within the ‘home‐ranges’ was also greater than the average of the AoS. Of all grivet monkey records in Eritrea, 63.7% were closer than 1500 m to the nearest river or riverbed, indicating the importance of riverine forest and woodland for grivet monkeys in the otherwise arid habitats. Conflicts between humans and grivet monkeys were reported from almost every site because both use the riverine habitats extensively. In 37.2% of the cases, the distance between a grivet monkey record and the nearest agricultural area (>5 ha) was less than 500 m and 31.8% of the monkey sites were found within 1000 m of the nearest village. An increasing human population (especially due to resettlement projects for refugees) and an intensification of agricultural activities, particularly in the riverine habitats through modern irrigation techniques, is likely to increase the conflict and will probably have a negative impact on the grivet monkey population in Eritrea.