THE OPTIMAL ALLOCATION OF TIME OVER THE DIVE CYCLE - AN APPROACH BASED ON AEROBIC AND ANAEROBIC RESPIRATION

Houston & Carbone (1992, Behav. Ecol., 3, 233-262) developed models th at predict the optimal allocation of time during the dive cycle motiva ted by the assumption that the diver uses aerobic respiration. In this paper this approach is extended using a model based on maximizing the proportion of time spent foraging to allow for the additional use of anaerobic respiration. Two models are presented. One, the 'switch' mod el, assumes the diver uses only one of the two metabolic pathways duri ng a dive. This model predicts the travel time (or water depth) at whi ch the diver switches from aerobic to anaerobic dives. Another, the 'm ixed metabolism' model, assumes a simultaneous mix of the two metaboli c pathways and predicts a shift in the proportional use of aerobic and anaerobic respiration with increasing water depth. In the mixed metab olism model, the predicted time in the food patch can change from a pa ttern qualitatively similar to the previous models, first increasing a nd then decreasing with depth, to a novel pattern with two peaks. The second peak in foraging time appears to be largely fuelled by anaerobi c respiration. The corresponding time on the surface changes from a pa ttern similar to the former models with one region with an abrupt uptu rn to a pattern with two such regions. These models provide insights i nto issues currently debated among diving physiologists concerning the degree to which and when divers should rely on anaerobic respiration. (C) 1996 The Association for the Study of Animal Behaviour