Social-insect fungus farming

cairostris (Cuvier’s beaked whale) and Mesoplodon densirostris (Blainville’s beaked whale). The authors find that both of these species undertake long, deep dives to capture deepwater prey. Diving is highly regular with most deep foraging dives being followed by an extended period of shallow dives and slow travel and resting near the surface. All foraging dives of both species are considerably longer than the estimated aerobic dive limits, suggesting that the whales return to the surface with an oxygen debt. “We propose that the shallow dives and the long periods in between foraging dives are needed to repay the oxygen debt before the next deep dive”, the authors report. Another consistent feature of the dive profiles, the authors find, is the slow ascent from the deep foraging dives, which remains a puzzle. The long ascents, which are acoustically inactive but involve active swimming, appear to divert substantial time away from foraging, suggesting that the animals are constrained by some physiological requirement or behavioural need that prevents them from optimizing foraging performance. The depths now found at which these whales forage may also throw light on the effects of naval sonar activities. Mass strandings of whales associated with sonar activity have revealed animals with gas and fat emboli in their bodies. The researchers consider whether sonar may disrupt the ascent after deep dives and that “the observed pathologies may follow from a behavioural response that has adverse physiological consequences”. They argue that regardless of the precise reason for whale strandings, “it is a pressing issue to develop effective mitigation protocols to reduce the accidental exposure to sonar”.