Arboreal habits and viper biology in the African rainforest: The ecology of Atheris squamiger

Aspects of the ecology of the arboreal viper Atheris squamiger are studied. A. squamiger is common in southeastern Nigeria, where it was observed main ly in secondary forest patches (both dry and flooded) and in shrublands, an d frequently also in primary forest patches. Conversely, it was rarely foun d in strongly altered habitats (farmlands, plantations, and suburbs). Adult sex ratio was nearly equal, and the proportion of immatures in the examine d sample did not differ significantly between sexes. The two sexes attained similar mean sizes, but females had modal and median lengths higher than m ales. Maximum male length was 67.0 cm, and maximum female length was 70.5 c m. Juveniles contained food in the gut much more frequently than the adults . A. squamiger fed primarily upon small mammals, and much more rarely upon scincid lizards and birds. No frogs were taken. There was an ontogenetic sh ift in taxonomical dietary preferences, with juveniles taking not only endo thermic but also ectothermic prey (lizards), and adults also taking birds b ut not reptiles. Moreover, among the mammals eaten, shrews were dominant in juveniles, whereas rodents were dominant in adults. Adults of both sexes w ere similar in terms of taxonomic dietary composition, but birds were preye d upon slightly more frequently by males. Prey consumed by the vipers were mainly nocturnal, both arboreal and terrestrial. There was a significant po sitive relationship between predator mass and prey mass. Activity of A. squ amiger was highest during the wet season (May to August), very high in the intermediate periods between dry and wet seasons (March to April, and Septe mber to October), and very reduced during the dry season (November to Febru ary), mainly during the early night hours (from 6 p.m. to 2 a.m.). Vipers w ere found on the ground more often during the night. Height of perches of v ipers on trees averaged 1.9 +/- 2.0 m (n = 34) during the day, and 0.4 +/- 1.1 m (n = 29) during the night.