ACTIVITY AND FORAGING BEHAVIOR IN THE PREDATORY FRESH-WATER LEECH NEPHELOPSIS-OBSCURA (ERPOBDELLIDAE)

1. The hypotheses tested were that foraging behavioural responses (num ber of meals consumed, the number of encounters with prey and feeding time) and activity (swimming time) of the freshwater predatory leech N ephelopsis obscura were higher in the dark than in the light, increase d with the size of the predator and increased with the length of the s tarvation period prior to feeding. 2. While swimming activity was long er in the dark, not all the foraging behaviour variables followed this pattern, There was an inverse relationship between swimming time and the number of meals consumed and the poor correspondence between swimm ing time and number of prey encounters indicates that swimming is not always directly associated with increased foraging and might be relate d to movements between micro-habitats. 3. The effect of body size on f eeding is complicated by its interaction with hunger levels and the ab ility of the predator to handle prey.