Impact of Market Hunting on Mammal Species in Equatorial Guinea.

Abstract

The impact of commercial hunting on forest mammals was studied in two regions on Bioko and Rio Muni in Equatorial Guinea, west Africa. Harvests were assessed from carcass counts in the main markets in the areas. A total of 10,812 carcasses of 13 species were recorded in Bioko, and 6160 carcasses of 30 species were recorded in Rio Muni. Biomass of harvested mammals was 111,879.63 kg in Bioko and 66,447.87 kg in Rio Muni. For the 12 prey species selected for study in Bioko, harvests totaled 7.15 animals/km2 or 62.93 kg/km2 . Harvests for the 17 prey species in Rio Muni were 3.22 animals/km2 or 24.06 kg/km2 . We used a model developed by Robinson and Redford (1991) to estimate potential harvests based on animal production rates. Total production was 147.90 animals/km2 and 139.12 animals/km2 in Bioko and Rio Muni, respectively. Potential harvest figures varied considerably by species. Comparison of actual and potential harvests showed that five primate species (Cercopithecus erythrotis, Cercopithecus nictitans, Cercopithecus pogonias, Cercopithecus preussi, and Mandrillus leucophaeus) and one ungulate (Cephalophus ogilbyi) in Bioko were being hunted unsustainably. Only two of the 17 species (Cercopithecus nictitans and Cephalophus dorsalis) in Rio Muni were being hunted unsustainably. Percent deviation of actual from potential harvests averaged 4.98 times greater than sustainable harvest in Bioko and 1.03 times greater in Rio Muni. For the two sites together figures ranged from close to 28 times greater than potential to 0.08% of the potential harvest. Although hunting methods and the commercialization potential of species may affect their presence in markets, these figures show that Bioko animals are heavily exploited, some of them unsustainably. This poses severe risks for the conservation of the island's unique fauna that must be addressed immediately. Impacto de la caza comercial sobre las especies de mamíferos en Guinea Ecuatorial.