The ecological distribution of Causus (Viperidae) in Nigeria, with special reference to Causus resimus and Causus lichtensteini, two species rarely recorded from this country.

New data for snakes of the genus Causus Wagler 1830 (Viperidae) are reported for Nigeria, with emphasis on their ecological distribution and biology. Causus rhombeatus (Lichtenstein 1823) was never observed during our long-term field study, and is probably a very rare species in Nigeria, confined to a small area in the north-east of the country. We confirmed that Causus maculatus (Hallowell 1842) is widespread in Nigeria, inhabiting a wide variety of ecological regions, from the rainforests of the south to the Sudanese savanna in the north. It feeds on amphibians, mainly ranid frogs. Causus resimus (Peters 1862) was reported to occur in Nigeria only on the basis of a few specimens without precise locality. We found three vouchers with known locality of capture in the Zoological Museum of Copenhagen, and we captured a few other specimens in the field. Although probably rare (given the very few captures), this species has a wide distribution in Nigeria, mainly in savannas and forest-derived savannas. It feeds on toads. Causus lichtensteini (Jan 1859) was occasionally captured in the swamp-forests of the Niger Delta (southern Nigeria), but seems to be absent from other forested regions of the country. It is also an anuran-eater