The northern coastal forests of Kenya are nationally and globally important for the conservation of Aders’ duiker Cephalophus adersi and other antelope species

Abstract

Aders’ duiker Cephalophus adersi is a critically endangered small antelope endemic to the coastal forests of east Africa. Threatened by habitat loss and hunting, the species was until recently known to persist only on Zanzibar, Tanzania, and in the Arabuko-Sokoke National Reserve, Kenya. However, more recent observations, have confirmed the occurrence of Aders’ duiker in Kenyan coastal forests north of the Tana River. This paper reports systematic camera trapping results for three sites in the Boni–Dodori coastal forest system north of the Tana and the only other known mainland site for Aders’ duiker, the Arabuko-Sokoke forest. From a total survey effort of 5,723 camera trap days, we demonstrated that the known area of occurrence for Aders’ duiker has more than doubled with occupancy values at or close to 100 % for all three northern sites. An index of relative abundance for Aders’ duiker was also one to two orders of magnitude greater at these sites compared to Arabuko-Sokoke. Application of a replicate count N-mixture model to camera trap data from Boni National Reserve resulted in an estimate of 7.3 Aders’ duikers/km2 (95 % CI 4.5–10.1/km2). The results also indicate higher densities of suni Nesotragus moschatus and Harvey’s duiker Cephalophus harveyi in the northern forests relative to Arabuko-Sokoke. Blue duiker Philantomba monticola was recorded at low density in Arabuko-Sokoke forest but not detected at the northern sites. These findings significantly improve the conservation prospects for Aders’ duiker and highlight the global importance of the northern coastal forests of Kenya.