Declining population of the Vulnerable common hippopotamus Hippopotamus amphibius in Bénoué National Park, Cameroon (1976–2013): the importance of conservation presence

Abstract

Populations of the common hippopotamus Hippopotamus amphibiushave undergone widespread decline as a result of habitat conversion and hunting for bushmeat and, increasingly, for ivory. North Cameroon holds important populations of large mammals, including the hippopotamus. The species' status and population trend are poorly known, and led CITES to suspend trade in hippopotamus trophies in 2013. Using the methodology of surveys conducted during 1976–1987, we conducted counts of the hippopotamus in Bénoué National Park during the wet season of 2011 and dry season of 2013, and drew on unpublished biannual density counts conducted by the Garoua Wildlife College, Cameroon, during 1989–2010. Counts along the 100 km stretch of the Bénoué River in the Park indicated a reduction from 400 individuals in 1987 to 188 in 2013. However, linear densities along a 15–32 km stretch in proximity to the Park headquarters and two tourist camps were constant during 1976–2013 (c. 3.7 individuals km ⁻¹). Hippopotamus distribution was negatively associated with the presence of the camps of gold diggers, which occupied the northern half of the Park. Observations of antelopes suggested they had a comparable distribution, unlike primates, which were distributed relatively evenly. Our results show the importance of year-round conservation presence in the Park, which could be achieved with adequate personnel, a functional road system, and reinforcement of operations in neighbouring sport-hunting areas.