At first, it was a case of mistaken identity: When the first live specimens ever seen of a rare whale species turned up on a New Zealand beach in 2010, local officials mistook them for a more common type of whale. After the two whales died, the officials took tissue samples and buried the carcasses. It was only several months later, when scientists at the University of Auckland in New Zealand ran a routine genetic analysis of the tissues, that anyone realized they had spotted for the first time ever a live spade-toothed beaked whale (Mesoplodon traversii).
"It was very exciting. These animals are only known from three skull fragments; we didn't know if the species was still extant or didn't exist anymore," says Rochelle Constantine, a marine mammal biologist at the university.
The two whales, a 5.3-meter-long female and 3.5-meter-long juvenile male that were originally mistaken for Gray's beaked whales, were exhumed for a morphological analysis that helped confirm distinctions from other species. The group reported their results on 6 November in Current Biology.
The 21 known species of beaked whales are among the most rarely sighted and least understood, says marine mammal researcher Tadasu Yamada of the National Museum of Nature and Science in Tsukuba, Japan. They inhabit the deep waters of the South Pacific, feeding on squid and small fish, and spend limited time at the surface. "It is probably best to think of these whales as surfacers rather than deep divers," says Robert Harcourt, a marine mammal researcher at Macquarie University in Sydney, Australia. "Sleeping, feeding, socializing, and mating all occur at depth, and so while we think of them as elusive, the reality is they inhabit a different sphere and one which is incredibly hostile to bipedal apes."
This means that while considered "rare," just how many spade-toothed beaked whales are living in the remote, deep parts of the ocean is unknown, Harcourt says. Yamada wonders what would have driven the evolution of the different skull morphologies seen on this species. But learning more about these animals won't be easy. "At least we now know what they look like," Constantine says, adding that this may prove useful in future ocean surveys.
"The significance of this finding is that once again we have evidence that our understanding of the biota of the deep oceans is still only (literally) scratching the surface," Harcourt says.