Night and day: evaluating transect methodologies to monitor duikers in the Dzanga-Sangha Protected Areas, Central African Republic

Status and ecology of forest ungulates in the Dja Faunal Reserve, Cameroon

Ungulates have undergone major declines in Central and West African forests as a result of bushmeat trade and habitat loss. Monitoring forest ungulate status is a critical conservation need. We undertook a systematic camera-trap survey of the 5260 km2 Dja Faunal Reserve, Cameroon’s largest protected area. We deployed cameras at 305 sites in eight grids across the reserve over 28,277 camera-trap days. We recorded 30,601 independent detections of 12 species of forest ungulate. The blue and Peters’ duikers were the most abundant, accounting for 82% of all ungulate detections, both with occupancy >85% in all survey grids. The black-fronted duiker was relatively widespread but rare. The white-bellied duiker and water chevrotain were found mostly in the southern part of the reserve. There were very few detections of sitatunga, forest buffalo and bongo. Our results suggest ecological partitioning among the more abundant duikers based on activity pattern and body size. The reserve faces many pressures including illegal subsistence and commercial hunting. Community surveillance and partnerships, with improved law enforcement are among measures being implemented by the Cameroon government to enhance security and ensure retention of the reserve’s World Heritage status.

Rapid dung removal by beetles suggests higher duiker densities in Central African rainforests

For many mammal species, converting dung density into population density requires accurate estimates of defaecation rate and dung survival time. The latter parameter probably varies seasonally. In Nki National Park, south-east Cameroon, we monitored 216 dung piles of the blue duiker Philantomba monticola and 373 of the red duiker group (Cephalophus spp.), major game animals in Central Africa, and estimated dung survival time across seasons. Mean survival time was 6.83 days in the major dry season and 1.21–1.81 in other seasons for the blue duiker, and 7.37 and 1.53–4.05 for red duikers, lower than the values conventionally used for density estimations in Central Africa (i.e. 18 days for the blue duiker and 21 days for red duikers). Overall, beetles removed half of the dung within 1 day of deposition. However, the proportion of dung piles that beetles removed was significantly lower in the major dry season, and other dung piles remained longer until they disappeared as a result of other factors. As shorter dung survival time results in higher estimates of population density, our findings imply that in forests with intense beetle activity, duiker densities are higher than those based on the conventional values of dung survival time. Duiker densities and dung survival time should be estimated simultaneously. To minimize the bias introduced by rapid removal of fresh dung by beetles, only fresh dung (< 3 hours old) should be monitored when estimating mean dung survival time.

Estimating forest antelope population densities using distance sampling with camera traps

Traditional transect survey methods for forest antelopes often underestimate density for common species and do not provide sufficient data for rarer species. The use of camera trapping as a survey tool for medium and large terrestrial mammals has become increasingly common, especially in forest habitats. Here, we applied the distance sampling method to images generated from camera-trap surveys in Dja Faunal Reserve, Cameroon, and used an estimate of the proportion of time animals are active to correct for negative bias in the density estimates from the 24-hour camera-trap survey datasets. We also used multiple covariate distance sampling with body weight as a covariate to estimate detection probabilities and densities of rarer species. These methods provide an effective tool for monitoring the status of individual species or a community of forest antelope species, information urgently needed for conservation planning and action.