Beaked whales are magnificent and mysterious. Some are rare but it is hard to know how rare, as there is still so much to learn about them.
They spend most of their lives diving deep into the ocean, and fill as little as 8 per cent of their time at the surface. This makes them the least understood cetaceans.
Ziphiidae (Ziffy-ee-day) is the scientific name for the beaked whales.
They are their own large diverse family with a zippy name. In Greek legend, Ziphius is a "water owl", which is appropriate for the broad, high-forehead face like an owl's. Another explanation is that it comes from the Greek word xiphos (zee-phos) meaning "sword", alluding to the protruding beaks that characterise this great family of whales.
Beaked whale bodies are supremely adapted to an extreme lifestyle of deep diving.
They must hold their breath for over an hour, dive into crushing water pressure, and then stealthily hunt nimble prey in the pitch black freezing cold.
Surviving deep diving is not just a question of breath holding.
Water pressure below a kilometre down would crush even the strongest submarines, and deep ocean temperatures are cold, about zero to 3 degreesC. Beaked whales have cracked these problems in ingenious ways.
Inside their collapsible chest, their lungs can deflate and the ribs can fold up so there is no internal gas hollow to be crushed.
Having no air in the lungs also reduces the absorption of nitrogen, the cause of the "bends".
Their spleens and livers are huge, storing extra oxygen-carrying blood, and they may process toxins building up on long dives.
Beaked whales also have streamlined, bulky bodies with grooves for their small side-flippers to tuck into, to improve dive speed while their large rounded forms conserve body warmth.
Human deep dive champions go into a trance-like state, aware that panicking so far from air would be fatal. Beaked whale brains are bigger than human brains, so they would need to conserve oxygen use too.
It is likely that they also go into a special dive mode. Beaked whales have a neat trick for up-loading dinner.
All species can rapidly expand grooves on either side of their throats and pull their tongue back smartly to slurp in a large quantity of food and water.
This technique explains why they are a "teeth-optional" family, with many species having no seizing or crushing teeth at all.
The complex skull shapes of beaked whales are cleverly adapted to send and receive sonar signals for precise navigation and food tracking in the total darkness of deep water.
The bulging melons at the front of many whales can focus a beam of sounds made in the blowhole. When the tell-tale echoes return, the dish shapes on the front of the skull help to collect the sound into the ears. Large brains process this information to create 3-D imagery.
Underwater, judging which direction sound is coming from is tricky, because sound travels much faster in water. Those forehead melons have just the right acoustic qualities to make directional hearing possible.
This sonar system is vital in the total darkness of deep water. A blowhole on top of the head evolution from a distant ancestor with two front facing nostrils. The long beaks that their family is named after are used to seize prey.
The Whanganui Regional Museum has an articulated skeleton of a southern beaked whale, Tasmacetus shepherdi, named in honour of George Shepherd, curator from 1926 to 1946.
Shepherd recognised that a whale corpse washed ashore near Hāwera was different from any whale he had seen before. It was unique and received a new genus name, Tasmacetus (Tasman sea whale), as well as the species name shepherdi, in honour of our George. Museum visitors can see this scientifically and historically important skeleton on exhibition.
Keith Beautrais is a scientist, teacher and conservationist who advises, researches and writes occasionally for the Whanganui Regional Museum.