For almost 150 years, no one had seen a spade-toothed whale. That’s not to say that the animal had gone extinct – no one had ever seen one alive. The first clue to its existence came in 1872, when Scottish geologist James Hector described an unusual jaw that had been collected from New Zealand’s Pitt Island a year earlier. Two more partial skulls would follow: another from New Zealand’s White Island in 1950 and the other from Chile’s Robinson Crusoe Island in 1986. But still, no one had seen the animal in the flesh.
Then, in December 2010, two of them washed up on Opape Beach in New Zealand.
A member of the public saw the whales, and reported them to the local Department of Conservation. By the time the staff members got there, both animals – a 5-metre-long female and a 3.5-metre-long male – had died. The team made measurements, took tissue samples, and buried the whales at the beach.
So far, so unspectacular—whale strandings are sadly all-too-common on New Zealand’s beaches, and everyone thought the pair were Gray’s beaked whales, the most common strandees. But their DNA told a different story. Kirsten Thompson from the University of Auckland sequenced two distinctive parts of their genome, and compared these to a library of sequences. They were a perfect match for the previously unseen spade-toothed whale. After all this time, we finally know what the animal looks like.
The spade-toothed whale (Mesoplodon traversii) is one of the 21 species of beaked whales, or ziphiids. They’re enigmatic animals. It seems that they spend their time diving to exceptional depths in search of food, so few people have ever seen one. New Zealand’s a good place to try. At least 13 species of beaked whales swim around its waters and many of them end up stranded on its beaches.
Telling these creatures apart is not easy. Only subtle differences in their size, teeth, beaks, and colours give away the different species. For example, compared to the Gray’s beaked whale that it was initially mistaken for, the female spade-toothed whale had a more prominent forehead, a white belly, dark flippers, a dark eye-patch, and a blackish-gray beak (the Gray’s beak, confusingly, is white). The smaller male, however, was remarkably similar to other juvenile beaked whales, and would be very difficult to distinguish in the field, if you were ever lucky enough to see one.
Whale biologists have gradually abandoned these arcane skills, in favour of genetic diagnostics. In 2002, DNA sequencing confirmed that the three existing pieces of spade-toothed whale bones were all from the same species, rather than from other beaked whales. Now, it has identified the two individuals that washed up on Opape Beach.
Whale strandings are unfortunate, but New Zealand has at least made good use of them. The nation has developed a co-ordinated national policy, where members of the public call the Department of Conservation after seeing a stranded whale. A team arrives, attempts a rescue, and collects tissue samples that are stored in a central archive. Thanks to this strategy, the country now has 20 years of records and specimens of rare species. The spade-toothed whale joins that list: the bodies of the two dead individuals have since been exhumed, and their skeletons are preserved at the Museum of New Zealand Te Papa Tongarewa.
With only two intact animals having been seen in the last 150 years, it seems safe to suggest that the spade-toothed whale is one of the world’s rarest whales, if not the very rarest. And if stranding is the only way of seeing these animals, perhaps we should be grateful that they’re as elusive as they are.
Are they still out there? Were these two individuals the last of their kind? No one knows. “We’re not sure why they are so rarely seen,” says Thompson. “It may be that they live in deep oceanic waters away from land so we don’t see them when they die, or it may be that there are very few of them. The answer remains an unknown.”
Reference: Thompson, Baker, van Helden, Patel, Millar & Constantine. 2012. The world’s rarest whale. Current Biology http://dx.doi.org/10.1016/j.cub.2012.08.055