Optimal diving and oxygen use

Abstract

Animals that hunt for food underwater and return to the surface for air (‘divers’) are limited by their ability to store oxygen. The aerobic dive limit (ADL) is the dive duration at which all the possible oxygen stores have been used. It has been claimed that models of optimal diving predict that divers will be close to this limit and that the data do not match this prediction. I characterize closeness to the ADL by the fraction ψ of the maximum amount of stored oxygen that is used during a dive. At the ADL this fraction is 1. I show that an optimal diver does not necessarily have a ψ close to 1 and point out that the key feature predicted by the model is that the diver should have no oxygen stores left when it returns to the surface. The data cited against optimal diving do not address this issue. • Animals that dive for food and return to surface for air are limited by oxygen stores. • Models claim that optimal divers should use nearly all their maximum oxygen stores. • I develop a measure of oxygen use for divers and illustrate it with data from whales. • I show that optimal diving does not predict that the maximum amount of oxygen is used. • I argue that the data cited against optimal diving do not address this issue.