By Dan Satherley
Two whales that beached in the Bay of Plenty on New Year's Eve, 2010, were members of the world's rarest whale species, scientists have discovered.
At the time they were misidentified as the relatively common Gray’s beaked whales, but DNA evidence has proved they were in fact seldom-seen spade-toothed beaked whales.
They are so rare, until then no one had ever knowingly seen one.
"It’s incredible to think that, until recently, such a large animal was concealed in the south Pacific Ocean and shows how little we know about ocean biodiversity," says lead scientist Rochelle Constantine.
The spade-toothed beaked whale, known to scientists as Mesoplodon traversii, was first spotted on Pitt Island in the Chathams in 1872. No one realised it was a completely new species however until 2002, when skull and jaw fragments recovered from museum archives were analysed and found to be of a unique species.
However, no one knew if the spade-toothed beaked whale still existed now.
On December 31, 2010, a 5.3m long mother and her 3.5m calf stranded and died on Opape Beach in the Bay of Plenty. It was assumed at first they were Gray’s beaked whales, which look very similar to the spade-toothed beaked whale, but are the most common whale to beach in New Zealand.
The Department of Conservation took tissue samples from the unlucky pair, and genetic analysis at the University of Auckland showed they were of the same rare species as the archived skull and jaw fragments.
"In New Zealand we have a very well established network whereby members of the public report stranded marine mammals to the Department of Conservation, which collects information and sends tissue samples to our laboratory at The University of Auckland," says Dr Constantine.
With the permission of Whakatohea Iwi Maori Trust and the Ngai Tama Haua hapu the whales' skeletal remains were exhumed for further study.
"This is the first time a spade-toothed beaked whale has been seen as a complete specimen, and we were lucky enough to find two of them," says Dr Constantine.
"This is a real New Zealand story – it’s all linked here, from the discovery of two of the bone fragments to the identification of the species and now the first sighting of the whales."
She says it's not known why the whales have proved to be so elusive. The skull and jaw fragments analysed in 2002 were discovered in the 1950s, and the only other specimen known to exist is part of a skull found in Chile in 1986.
"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."
Dr Constantine's research has been published in the latest issue of Current Biology.