Topography-derived variables provide insight into habitat occupancy of a cryptic snake, Bitis atropos

Understanding species’ habitat use is fundamental for conservation and management. However, quantifying habitat use for small cryptic species is limited by imperfect detection during field surveys and the lack of habitat data at meaningful spatial scales. Topographically-derived habitat variables from digital elevation models (DEMs) have the potential to overcome these limitations. Here we used DEM-derived topographic variables as fine-scale proxies for abiotic conditions to study site-occupancy patterns of the berg adder (Bitis atropos), a small-bodied cryptic viper. We carried out seven repeated field surveys across 219 hectares in a mountainous protected area in north-eastern South Africa to estimate snake detection probability and occupancy using maximum likelihood methods. Although snakes occurred across a third of the surveyed habitat, they were only detected 40% of the time during the springtime when detection was highest. Results showed that these snakes preferred north-west facing, mid and upper slopes, which are exposed to afternoon sun and presumably higher ambient energy. Our results demonstrate the value of using DEM-derived topographic variables for ecological studies where habitat data are either unavailable or inappropriate, thereby providing valuable insights into habitat use of cryptic and difficult to detect species

The medical threat of mamba envenoming in sub-Saharan Africa revealed by genus-wide analysis of venom composition, toxicity and antivenomics profiling of available antivenoms

Mambas (genus Dendroaspis) are among the most feared of the medically important elapid snakes found in sub-Saharan Africa, but many facets of their biology, including the diversity of venom composition, remain relatively understudied. Here, we present a reconstruction of mamba phylogeny, alongside genus-wide venom gland transcriptomic and high-resolution top-down venomic analyses. Whereas the green mambas, D. viridis, D. angusticeps, D. j. jamesoni and D. j. kaimosae, express 3FTx-predominant venoms, black mamba (D. polylepis) venom is dominated by dendrotoxins I and K. The divergent terrestrial ecology of D. polylepis compared to the arboreal niche occupied by all other mambas makes it plausible that this major difference in venom composition is due to dietary variation. The pattern of intrageneric venom variability across Dendroaspis represented a valuable opportunity to investigate, in a genus-wide context, the variant toxicity of the venom, and the degree of paraspecific cross-reactivity between antivenoms and mamba venoms. To this end, the immunological profiles of the five mamba venoms were assessed against a panel of commercial antivenoms generated for the sub-Saharan Africa market. This study provides a genus-wide overview of which available antivenoms may be more efficacious in neutralising human envenomings caused by mambas, irrespective of the species responsible. The information gathered in this study lays the foundations for rationalising the notably different potency and pharmacological profiles of Dendroaspis venoms at locus resolution. This understanding will allow selection and design of toxin immunogens with a view to generating a safer and more efficacious pan-specific antivenom against any mamba envenomation