Quantifying the response of tree hyraxes (Dendrohyrax validus) to human disturbance in the Udzungwa Mountains, Tanzania

Quantifying the effects of human disturbance on rare species is crucial for conservation. The eastern tree hyrax (Dendrohyrax validus), restricted to East Africa, is one of the region’s least studied mammals. This study assesses the effect of hunting and logging on density and calling behavior. We evaluate three methods for estimating relative density: circular plot counts of calling individuals, latrine counts, and daytime transect counts. Circular plots show that the density of calling individuals within one forest is positively related to canopy cover. Furthermore we estimate densities of 17.3 calling individuals ha in a little-disturbed forest, 12.1 in a lightly disturbed forest, and zero in an intensely hunted and formerly logged forest. Other methods support this trend, thus confirming that D. validus is dependent on intact forest. Estimation of hyrax density (and relative density) is however highly problematic and the magnitude of the trend varied between methods. Despite methodological problems, the results clearly highlight the discordance between Forest Reserve legislation and management, a conservation concern throughout the tropics.