Predation capacity of tadpoles (Bufo regularis) using African catfish Heterobranchus longifilis larvae: impact of prey characteristics on vulnerability to predation

Rates of predation by tadpoles of Bufo regularis on larvae of the African c atfish Heterobranchus longifilis were determined under controlled laborator y conditions. Predation rates were high on early stage yolk-sac and first-f eeding larvae, which have a poorly developed escape ability. A steady decli ne in predation rates was found with an increase in the size of the larvae. Predation rates were significantly related to prey density. The relationsh ip between larval biomass eaten and biomass available suggested that tadpol es were not satiated when feeding on the largest larvae, probably because o f the improved escape ability of these larvae. Prey movement was not found to be an important factor eliciting predation by tadpoles. Starved larvae w ere more vulnerable to predation because of a poor escape response. Our res ults indicate that tadpole predation may represent a substantial source of mortality of catfish larvae in earthen primary nursing ponds.