REPRODUCTIVE-BIOLOGY AND FOOD-HABITS OF HORNED ADDERS, BITIS-CAUDALIS(VIPERIDAE), FROM SOUTHERN AFRICA

Kerned adders (Bitis caudalis) are small heavy-bodied viperid snakes w idely dis tributed across a range of habitat types in southern Africa. Measurement and dissection of 580 preserved specimens in museum colle ctions provided information on morpholopy, food habits, and reproducti ve biology of this species. in particular, it enabled us to assess the effects of sex and habitat type (arid to mesic) on adult body sizes a nd shapes, dietary composition, and reproductive output. Female horned adders mature at larger sizes than do males and grow much larger. At the same snout-vent length, females have larger heads and shorter tail s than do males. Arid-zone snakes are longer and thinner than conspeci fics from more mesic areas and have longer tails and larger heads. Hor ned adders feed primarily on lizards (especially lacertids, skinks, an d geckos) but also take other small vertebrates. Dietary composition v aries according to the snake's body size, sex, and geographic location : endothermic prey are taken mostly by larger snakes; by females rathe r than males; and by arid-zone rather than mesic-habitat snakes. Most prey are small relative to predator size, especially in large snakes. Litter sizes (3-19 offspring) increase with maternal body size, with n o significant geographic differences in this relationship. However, re productive frequency las inferred from the proportion of adult females that were reproductive when collected) was significantly higher in me sic-habitat snakes (> 50%) than in their arid-zone relatives (15%). Ha bitat-associated differences in resource availability may have affecte d traits such as body size and shape, degree of dietary specialization , growth rates and female reproductive frequencies.