DIURNAL VARIATION OF SPACING AND FORAGING BEHAVIOUR IN TROPHEUS MOORII (CICHLIDAE) IN LAKE TANGANYIKA, EASTERN AFRICA

摘要

Diurnal variation of behaviour was investigated in the epilithic algae Feeder Tropheus moorii in Lake Tanganyika. Territories. home ranges and four behavioural categories were recorded during the diurnal cycle. All four behavioural categories (foraging, locomotory activity, resting behaviour and total social interactions) pattern. Foraging activity was maximum between 12.30 h and 16.30 h, and the observed diurnal pattern was similar to the rhythm found in a great number of marine algae feeders. In contrast to previous observations individuals displayed both territorial and non-territorial activities during the day, expressed by specific colour- and behaviour patterns. The time spent in the own territories also varied with day time and was maximum between 12.30 h and 16.30 h. Non-territorial aggregations of several individuals outside territories were particularly observed during dawn and dusk. Territories may primarily function as feeding territories since foraging was the most frequent behaviour. Non-territorial activities may allow individuals to utilize additional food sources and the aggregation of several individuals at dawn and dusk may indicate their behaviour at night. The observed diurnal rhythms of behaviour, together with the previously described complex social behaviour, and the altered mating system of Tropheus, may have evolved as a consequence of extreme sedentarity and close association to rocky substrate in order to optimize resource utilization.