Rarest whales make their appearances

Migaloo SW

Migaloo diving © SW

(Migaloo was first seen in Australia waters in 1991 as a juvenile and is part of the east Australian humpback population which numbers up to 17,000, as reported by the White Whale research Centre.)

Spade-toothed whale was first mistaken for a Gray’s beaked whale but later identified by its DNA © SW

However, the other whale is even rarer - in fact the rarest whale in the world - and it's only just been recognised by its DNA for the first time from a sighting in 2010.

The spade-toothed whale (Mesoplodon traversii) is a very little known (and also the rarest) species of beaked whale. It was first named from a partial jaw found on Pitt Island (New Zealand) in 1872, reported and illustrated in 1873, but until now the animals themselves have remained entirely hidden from human view.

In the 140 years since they were first discovered, the only sign that the creatures' continued existence lay in two partial skulls found in New Zealand in the 1950s and Chile in 1986.

Now scientists have reported a complete description of the whales, which are thought to spend most of their lives in the deep waters of the Pacific Ocean, only rarely coming to the surface.

The Mother and her male calf were stranded and died on Opape Beach at the northern tip of New Zealand in December 2010 but were initially thought to be of a much more common species known as Gray's beaked whales.

It was only after routine DNA analysis that experts realised their true identity. They published their findings this week.

Dr Rochelle Constantine of the University of Auckland said: 'This is the first time this species — a whale over five meters in length — has ever been seen as a complete specimen, and we were lucky enough to find two of them.

Because the animals had never been seen very little is known about their behaviour, but writing in the Current Biology journal, the researchers suggested they were likely to be 'exceptionally deep divers, foraging for squid and small fish and spending little time at the surface.'

Dr Constantine said it was unclear why the species has been so elusive, but added: 'It may be that they are simply an offshore species that lives and dies in the deep ocean waters and only rarely wash ashore. New Zealand is surrounded by massive oceans. There is a lot of marine life that remains unknown to us.'