Captivity can provide a resource-rich environment for snakes which may lead to over-conditioning of individuals. We compared captive and wild populations of Bitis arietans to see if a difference in scaled mass index (SMI) existed between the samples. Male B. arietans had significantly higher SMI in captivity than in the wild; there was no difference between wild and captive females. A sex-related difference in SMI between wild male and female B. arietans, evident in the wild, was not found in captivity. These results suggest that the captive management of B.arietans may require review to prevent over-conditioning of male snakes, and that this may be informed by further comparative research on wild and captive populations of this species. Keywords: Body condition, captivity, scaled mass index, Viperinae