Marine mammals have exceptional deep-diving abilities. For example, southern elephant seals can stay underwater for up to two hours at 2100 metres and sperm whales can spend more than an hour at depths below 2200 metres.
Deep-diving marine mammals have special physiological adaptations in their respiratory and cardiovascular systems, blood, and peripheral tissues. This adaptation results in highly efficient ventilation, enhanced oxygen storage, well-regulated transport and delivery of respiratory gases, and extreme hypoxic and pressure tolerance amongst other things. In addition, recent scientific discovery showed that myoglobin, a protein that stores oxygen in the blood of all mammals, has a “non-stick” property in marine mammals, which means that large amount of oxygenated blood can be stored in their muscles without clogging up.
Beaked whales are known to be extreme divers. Specifically, short-term data of Cuvier’s beaked whale (Ziphius cavirostris) or goose-beaked whale showed that they routinely dive deeper than 1000 meters (mesopelagic depth) for an hour or longer.
Cuvier’s beaked whale is the most widely distributed and one of the most frequently spotted beaked whales. It has a smooth-sloping forehead with an indistinct beak and no obvious melon. Cuvier’s beaked whales can be found in offshore waters, often at upwelling areas, from the warm tropics to the cold temperate waters, and it feeds on squid, deep-sea fish and, rarely, crustaceans. It has two diving modes: long, deep foraging expeditions that are characterised by echolocation; and shorter, shallower, silent dives which purpose is still not understood.
Interest in Cuvier’s beaked whales arose when individuals became stranded during naval sonar exercises and have been reported to have symptoms of decompression sickness. This seemed like a strange injury for an animal that is used to diving into great depths. Some suggest they could interpret underwater noise coming from military sonar as approaching killer whales.
Recently, with the use of electronic tags, scientist were able to collect long-term data on the diving behaviour of Cuvier’s beaked whale off the coast of Southern California. They revealed, for the first time ever, that this species is able to dive to 3000 metres where it can spend up to two hours. So it is the Cuvier’s beaked whale that can do the deepest and longest dives amongst marine mammals!
By Wanda Bodnar
Image source: Daniel Webster and National Geographic