In another example of how little we know about the natural world, scientists recently got their first up-close glimpse at the rare and elusive spade-toothed beaked whale (Mesoplodon traversii). Tragically, the discovery was not of living whales but a mother and her male calf that died after beaching themselves.
Until now, the spade-toothed beaked whale has only been known to science from three partial skulls found in New Zealand and Chile in 1872, 1950 and 1986. This is the first time that full bodies for this species have ever been studied. Even that is a stroke of luck since the two whales were first incorrectly identified as related Gray's beaked whales (M. grayi), which look quite similar to the spade-toothed species.
The two spade-toothed whales were found stranded on New Zealand's Opape Beach in December 2010. They died soon after. The New Zealand Department of Conservation (DOC) was called in to photograph the animals and collect measurements—the female was 5.3 meters long, while the juvenile male was 3.5 meters—and to collect tissue samples, which turned out to be the key to unmasking the whales' true identity. The DOC has routinely conducted DNA tests on beached beaked whales for the past 20 years. At least a dozen other beaked whale species can be found in the waters around the island nation.
"When these specimens came to our lab, we extracted the DNA as we usually do for samples like these, and we were very surprised to find that they were spade-toothed beaked whales," Rochelle Constantine of the University of Auckland said in a prepared release. "We ran the samples a few times to make sure before we told everyone."
As Constantine and her fellow researchers write in a paper published today in the journal Current Biology, very little is known about the world's 21 species of beaked whales. The cetaceans "are thought to be exceptionally deep divers, foraging for squid and small fish and spending little time at the surface. Due to similarities in their external morphology, species are very difficult to distinguish and, given their elusive habits, are rarely seen at sea." Most of the beaked whales look so alike externally that species can only be easily determined by examining the teeth of mature males, but that is not an option for females or juveniles. The species do vary by color but their skin breaks down quickly after death, further hampering identification efforts.
The researchers did come up with a few details to describe this species. The found a prominent melon (an organ behind the forehead that may play a role in echolocation), a dark gray or black rostrum, a dark eye patch, a white belly and dark flippers, all of which distinguish it slightly from other beaked whales.
Although this research provided scientists with their first full description of the spade-toothed beaked whale, Constantine and her fellow researchers do not know why the species has so rarely been seen. "It may be that they are simply an offshore species that lives and dies in the deep ocean waters and only rarely wash ashore," she said. "New Zealand is surrounded by massive oceans. There is a lot of marine life that remains unknown to us."
The skeletal remains of the two whales, which had initially been buried, have now been taken to the Museum of New Zealand Te Papa Tongarewa for further study.
Photos: The stranded female spade-toothed beaked whale, courtesy of New Zealand Department of Conservation