Noninvasive genetic analysis for assessing the abundance of duiker species among habitats in the tropical forest of Moukalaba, Gabon

Abstract

We investigated the relative abundance of four duiker species and the environmental effect including human impacts on their abundance in the forest of Moukalaba, Gabon. We counted and collected fresh faeces from duikers in thirteen 2-km line transects established in different types of vegetation. Genetic species identification showed that blue duiker (Philantomba monticola), Ogilby’s duiker (Cephalophus ogilbyi, which might include the sister species Peter’s duiker Cephalophus callipygus), bay duiker (Cephalophus dorsalis), and yellow-backed duiker (Cephalophus silvicultor) coexisted. Genetic analyses successfully identified Ogilby’s and bay duiker, which are difficult to discriminate using other methods. The blue, Ogilby’s, and yellow-backed duikers were found in all transects. The dung abundance of bay duiker was quite low compared to other duiker species. This result suggests the importance of accumulating information regarding the abundance of each duiker species for updating their conservation status. The dung count method with genetic species identification may be useful for this purpose. The dung abundance of Ogilby’s duikers and blue duikers was affected by human impacts, while that of yellow-backed duikers was not affected by human impacts. The dung abundance of Ogilby’s duikers was lower in young secondary forests, which are regenerating after significant human disturbance. In contrast, generalized liner mixed model showed that the dung abundance of blue duikers was not affected by vegetation type and was lower in transects nearer to the villages, which might be due to past hunting activity. The difference in human impacts among duiker species should be considered for their conservation management.