Living With Hyraxes: Biogeography and Comparative Ecology of West African Fornasinius Beetles

Abstract

Among the flower beetles (Scarabaeidae, Cetoniinae), the Goliathini comprise several genera of medium- and large-sized beetles widely distributed in sub-Saharan Africa. In this tribe, the genus Fornasinius Bertoloni, 1853, includes two species found in West Africa: F. higginsi (Westwood) and F. klingbeili Zöller, Fiebig,and Schulze. In this study, we present new data on the comparative ecology and biogeography of these two species, including sex ratio, population structure by size, monthly activity patterns and habitat features at two different spatial scales. These observations were conducted, mostly opportunistically, over a 20-year period in Cote d'Ivoire, Ghana and Togo. Both species exhibited similar overall population structure and morphometrics. They were characterised by a male-skewed adult sex ratio (with possible bias), male-larger sexual size dimorphism and consistent population structure by size; the two species are seemingly parapatric (with the potential contact zone being separated in eastern Ghana by the Volta River and Volta Lake). Both are primarily found in the vicinity of trees that contained middens of hyraxes, such as Dendrohyrax dorsalis (F. higginsi), Dendrohyrax interfluvialis (F. klingbeili) and Procavia capensis (F. klingbeili). F. higginsi has been primarily observed in forest habitat, while F. klingbeili was found in both forests and Guinea savannahs. Occurrence sites of F. higginsi were predominantly characterised by higher tree cover, less bare areas and built-up zones. Although these beetles may be locally abundant within hyrax middens, they typically occur in only a relatively small number of sites within their preferred habitat. Monthly activity patterns differed between the two species. Although adults of both species were observed throughout the year, sightings of F. higginsi were more common during the wet season, whereas F. klingbeili sightings were more frequent in the dry season. The observed differences in monthly activity patterns between these ecologically and morphologically similar species may help to minimise interspecific competition in potential—yet unknown—sites of syntopy. Although some Fornasinius populations might be locally threatened by deforestation or overhunting of hyraxes, the careful management of hyrax populations should adequately ensure the conservation of these two beetle species.