Aerobic dive limit: how often does it occur in nature?

Diving animals offer a unique opportunity to study the importance of physio logical constraint in their everyday behaviors. An important component of t he physiological capability of any diving animal is its aerobic dive limit (ADL). The ADL has only been measured in a few species. The goal of this st udy was to estimate the aerobic dive limit from measurements of body oxygen stores and at sea metabolism. This calculated ADL (cADL) was then compared to measurements of diving behavior of individual animals of three species of otariids, the Antarctic fur seal, Arctocephalus gazella, the Australian sea lion, Neophoca cinerea; and the New Zealand sea lion, Phocarctos hooker i. Antarctic fur seals dove well within the cADL. In contrast, many individ uals of both sea lion species exceeded the cADL, some by significant amount s. Australian sea lions typically dove 1.4 times longer than the cADL, whil e New Zealand sea lions on average dove 1.5 times longer than the cADL. The tendency to exceed the cADL was correlated with the dive pattern of indivi dual animals. In both Antarctic Fur Seals and Australian sea lions, deeper diving females made longer dives that approached or exceeded the cADL (P < 0.01, r(2) = 0.54). Australian and New Zealand sea lions with longer bottom times also exceeded the cADL to a greater degree. The two sea lions forage on the benthos while the fur seals feed shallow in the water column. It ap pears that benthic foraging requires these animals to reach or exceed their aerobic dive limit. (C) 2001 Elsevier Science Inc. All rights reserved.