Ziphiidae

About the beaked whales

Ziphiids are medium-sized whales with a pronounced beak, a pair of converging grooves on the throat, and shallow depressions into which the flippers can be tucked flush with the body. In most genera the teeth have been reduced to a single pair in the lower jaw that erupts only in adult males; the animals feed by suction and do not need them. What the tusks are for is visible on the animals themselves — mature males are covered in parallel linear scars from fighting each other, and a male’s tooth shape and position is often the only reliable way to tell one species from another.

They are extreme divers. Cuvier’s beaked whale has been recorded at nearly three thousand metres and, separately, holding a dive for three hours and forty-two minutes — the deepest and the longest breath-hold dives measured in any mammal. Foraging happens far below the surface on deep-water squid, and the animals spend very little of the day where they can be seen.

The consequence is a family being described in real time. Several species are known from a few dozen specimens; one, the spade-toothed whale, was not recorded alive anywhere in the world until 2010. Three species have been named or resurrected since 2014. The same acoustic sensitivity that makes them such specialised divers also makes them the group most strongly associated with mass strandings following naval mid-frequency sonar exercises.