Beaked Whales

Adult female Cuvier’s beaked whale (Ziphius cavirostris). Photo by Robin Baird.

There are entire species of large mammals living today on Earth which have never been seen alive by humans.  Even though they can grow larger than elephants, their numbers and habits are unknown.  We might not even know all extant species in the family.  These mystery mammals are the beaked whales (family Ziphiidae) masters of deep ocean diving.  The family is comprised of at least 21 different species, only 3 of which are well known (thanks to whale hunting in previous centuries). Beaked whales are poorly understood because they are rarely on the surface of the ocean where we can observe them.  They are capable of diving more than 1,899 meters (6,230 feet) and can stay underwater for almost an hour and a half.  Beaked whales live in the black–down among the underwater seamounts, canyons, and abyssal plains.  We only know them from the examination of dead specimens: indeed, for some species of beaked whales that is quite literally true and they have only been seen when dead.

Small Beaked Whales (an illustration by Brett Jarrett)

Beaked whales grow to sizes of 4 to 13 metres (13 to 43 ft) depending on the species.  They are sexually dimorphic—the males are a different size than the females.  Additionally male whales have prominent domed foreheads and a pair of fighting teeth for dueling and sexual display (these teeth do not fully develop in females).  Beaked whales feed on squid, and, to a lesser extent, fishes and invertebrates which they capture from the ocean bottom by means of suction.  In order to produce this suction effect, the whales have highly nimble tongues and throat grooves.

The most distinctive features of beaked whales (save perhaps from their rostral “beaks”) are the body features which allow them to dive so deeply and then hunt in the dark crushing waters.   The lungs of beaked whales collapse at a certain pressure—most likely as a way to minimize the dangers of nitrogen transfer. Their livers and spleens are huge in order to deal with the dangerous metabolic bi-products of prolonged periods when they are unable to breathe.  Additionally, their blood and muscle tissue is capable of capturing and storing substantially greater quantities of oxygen than the tissue of other mammals.  Beaked whales can pull their pectoral flippers into grooves which run along the sides of their bodies and thus become more streamlined.

Sowerby’s Beaked Whale (Mesoplodon bidens)

In order to find their way in the deep ocean, the whales rely on sophisticated acoustic echo-location organs.  Lips behind the blowhole produce high pitched vibrations which bounce off of prey and obstacles.  Echoes from these vibrations are then picked up and focused into the whales’ sensory organs by special fat deposits and bone structures.   Unfortunately this method of echolocation seems to make beaked whales extremely sensitive to sonar.  Resurfacing whales are unable to avoid the amplified sound waves and can suffer injuries to their sensory organs (or even to their large delicate livers).  Additionally, it is theorized that Beaked whales may try to resurface too quickly to avoid sonar and therefore risk decompression sickness.

(Photo: credit Nan Hauser & Hoyt Peckham, CCRC)

Humankind has also been fishing ever deeper waters as fish stocks crash—which involves the whales in by-catch issues.  Hopefully we will learn more about this family of enigmatic divers (and become more responsible stewards of the ocean) so that the beaked whales do not vanish before we even get to know them.

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