Marine biologists have described a new species of beaked whale known only from seven specimens found stranded on tropical islands in the western and central Pacific.
Mother, right, and calf of the Deraniyagala‘s beaked whale (Mesoplodon hotaula) at Palmyra Atoll in 2007. Notable are the cookie-cutter shark bites healed in dark skin callercolor, pronounced melon and beak, and large blow hole. Image credit: S. Baumann-Pickering, via R.L. Brownell et al.
Beaked whales are the members of Ziphiidae, a little-known family of toothed whales distantly related to sperm whales.
These aquatic mammals have elongated beaks and are moderate in size, measuring up to 13 m and weighing up to 15 tones.
They are found in deep ocean waters beyond the edge of the continental shelf throughout the world’s oceans.
“They are rarely seen at sea due to their elusive habits, long dive capacity and apparent low abundance for some species. Understandably, most people have never heard of them,” said Dr Merel Dalebout from the University of New South Wales, Australia, the lead author of the paper published in the journal Marine Mammal Science.
In 1963, Dr P.E.P Deraniyagala of the Sri Lanka’s National Museums of Ceylon described a 4.5-m-long blue-grey beaked whale found stranded near Colombo as a new species, Mesoplodon hotaula. The Deraniyagala‘s beaked whale was given as a common name.
However, in 1965, biologists reclassified Mesoplodon hotaula as an existing species – the Ginkgo-toothed beaked whale (Mesoplodon ginkgodens).
“Now it turns out that Dr Deraniyagala was right regarding the uniqueness of the whale he identified,” Dr Dalebout said.
“While it is closely related to the Ginkgo-toothed beaked whale, it is definitely not the same species.”
Dr Dalebout with colleagues used a combination of DNA analysis and physical characteristics to describe Mesoplodon hotaula from other seven specimens.
They were able to get good quality DNA from tissue samples from only one specimen. For the others, they drilled the bones of the whales in order to analyze short fragments of ‘ancient DNA’ relying on techniques commonly used with old sub-fossil material from extinct species.
They also studied all other known beaked whale species to confirm the distinctiveness of the Deraniyagala’s beaked whale, including six specimens of the closely related, gingko-toothed beaked whale.
“A number of species in this group are known from only a handful of animals, and we are still finding new ones, so the situation with the Deraniyagala’s beaked whale is not that unusual,” Dr Dalebout said
“For example, the Ginkgo-toothed beaked whale, first described in 1963, is only known from about 30 strandings and has never been seen alive at sea with any certainty. It’s always incredible to me to realize how little we really do know about life in the oceans. There’s so much out there to discover.”
With the discovery of Mesoplodon hotaula, there are now 22 recognized species of beaked whales.