Tuesday, February 19, 2013

First Sighting of the Spade-Toothed Whale

by kellc, This post originally appeared at Future Science Leaders of Science World.

Current Biology Today: “We can now confirm that the spade-toothed whale is extant and for the first time we have a description of the world’s rarest and perhaps most enigmatic marine mammal.”
In December 2010, 2 whales stranded and died on a remote beach in New Zealand. This was remarkable because it was a peculiar-looking whale, and was initially identified as the relatively common Gray’s beaked whale (Mesoplodon grayi), until further tests were run. Researchers at the University of Auckland sequenced 2 regions of mitochondrial DNA and shockingly found a match to the Spade-toothed whale (Mesoplodon traversii). Until 2010, the Spade-toothed whale had never been seen dead or alive, and was only known from 3 bone fragments. It was the rarest and most enigmatic of whales, and is still one of the least understood large mammalian species today. This stranding in December 2010 was particularly significant because it was the first time a whole specimen of the species had ever been discovered. Through this, researchers were able to note its physical anatomy and learn more about its morphology and DNA.
Spade-toothed whale
Despite this, the Spade-toothed whale has still never been seen alive. Why is it so rarely seen, despite being a large animal of over 5 metres long? The Spade-toothed whale is a member of the genus Mesoplodon, a branch of the family Ziphiidae, or beaked whales, and this family as a whole is still very poorly understood. There are 14 species in the genus Mesoplodon and yet these species are rarely seen or observed. Why is this? The beaked whales typically live far from the shore, and are very deep divers – they can dive over half a kilometer, and for almost 90 minutes. The Mesoplodon are also very difficult to identify at sea. For these reasons, they have averted public scrutiny and were, and continue to be, very mysterious.
Until recently, these bones were the only known part of the spade-toothed whale
The Spade-toothed whale and other beaked whales, despite being poorly understood, are not free from harm. After strandings, we are finding increasingly high levels of toxic chemicals in their blubber. They are also prone to entanglement in fishing nets and ingesting plastic bags. There is also the issue of decompression sickness; as deep divers they need to be careful when surfacing after a deep dive to avoid hemorrhaging or developing emboli, but this ability has been compromised by sonar exercises, which interfere with their behavior and surfacing pattern. 2 species of beaked whale have thus far been identified as being particularly vulnerable to sonar, as port-mortem examinations of these species have shown symptoms of decompression sickness, like hemorrhaging near the ears and the presence fat/gas emboli. Sonar could also be responsible for mass strandings of beaked whales. However, since there is so little known about beaked whales, conservation efforts are difficult. We don’t know their numbers in the sea, or population trends, or even basic behavioral patterns! Hopefully, with more effort, resources, developing technology and research, we will continue to study and to gain information about these enigmatic whales.
About this contributor: kellyc is an ocean lover and high school student, and is particularly fascinated by whales. She enjoys being outdoors, writing, traveling and meeting new people.

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