These are some of the best photos ever taken of True's beaked whale © Robbins et al. 2019

First confirmed sighting of True's beaked whale in the north-east Atlantic

The sighting of one of the world's rarest species of whale in the Bay of Biscay confirms for the first time that the marine mammals live in this region of the Atlantic.

The pictures also show that one whale had two additional teeth, something which has never been seen in this species before, highlighting just how little we know about these elusive creatures.    

Beaked whales are one of the least known groups of mammals. Living at extreme depths in the open oceans, it is exceedingly difficult to study them meaning that we know practically nothing about the animals.

When these whales surface, it is typically very brief and inconspicuous as they take a breath before plunging back into the deep sea. This means that even when these animals are seen at the surface, identifying their exact species is often difficult.

But during a survey of the Bay of Biscay by the citizen science charity ORCA, a group of beaked whales were observed breaching by the side of a ferry. During this encounter, the volunteers were able to snap hundreds of photos of at least four different individual whales.

These images were then assessed by multiple experts who confirmed that the animals seen were one of the rarest species of whale in the world: True's beaked whale (Mesoplodon mirus).

The images showed at least four different individuals breaching by the side of the ferry © Robbins et al. 2019

Ellen Coombs, a PhD research at the Museum, has been involved in writing up the sightings in a paper, along with Travis Park lead author James Robbins, published in the journal PeerJ.

'What is exciting is that these beaked whales haven't been seen live in that part of the world before,' says Ellen. 'There have been sightings before but they haven't been verified, so what makes this thrilling is the photographic evidence.'

In fact, the images are thought to be some of the best ever photographs taken of live True’s beaked whales.

James Robbins says, 'This species is rarely reported as having been seen in the North East Atlantic, with most of the very limited information we have coming from individuals stranded on beaches.'

Deep divers

There are thought to be at least 22 species of beaked whales, but due to their lifestyle only around three of these are known about in any detail at all, and even that is patchy.

'Because of their behaviour - that they are such deep diving animals - they don't tend to come to the shore that often where most people whale watch,' says Ellen. 'That they can be underwater for up to two hours so also means it is really hard to get any data on them.'

On top of this, it is thought that the whales just aren't particularly numerous. 'They are classified as rare or data deficient,' continues Ellen. 'All of those compounding factors just make for a very difficult group to study.'

The Bay of Biscay is a deep stretch of water that comes right into the shoreline between France and Spain © Eric Gaba/Wikimedia Commons

The Bay of Biscay is one of the best places to see whales and dolphins in Europe. The geology of the region means that the continental shelf extends far into the bay. This allows for these deep water species, such as sperm and beaked whales, to come much closer to the shore than in other places.

Over the years, there have been reports of people seeing True's beaked whale in the bay. These have been impossible to verify, particularly considering that the area is also frequented by other species of beaked whale such as Cuvier's. 

These images now give conclusive evidence that True's beaked whale lives in the north-west Atlantic around western Europe and in the coastal waters of the UK.

'If we're seeing species this rare in multiple pods, the finding highlights how important the area around the UK and the Bay of Biscay is for conservation,' says Ellen.

 Extra teeth

It wasn't just the pictures of the whales in general that excited Ellen and her colleagues, but also what they seemed to show in one individual.

Beaked whales can be identified by their tusks. Unusually amongst toothed whales, the animals only have a single pair of teeth in their bottom jaw. While in female beaked whales these remain hidden in their gum tissue, in the males the tusks erupt out of their mouths and are thought to play a role in fighting for mates. 

The pictures alread seemed to show something rather curious, as one of the males appeared to have an extra set of teeth © Robbins et al. 2019

The position of these tusks in the mouths of the males can help to confirm the identification of a species. For example, in male True's beaked whales the tusks are found right at the tip of the lower jaw.

Some of the images from the Bay of Biscay seemed to show a male True's beaked whale with the tusks clearly visible, but they also appeared to show something else. Directly behind these two tusks it looks like there are another pair of erupted teeth.

To try and find out if this has been seen before, Ellen and Travis looked at all the True's beaked whale specimens held at the Museum and the Smithsonian. Paying careful attention to the bone surrounding the two known tooth sockets, they found no evidence in any of the museum specimens for additional teeth.  

'It could just be an individual mutation in that one specimen, we can't rule that out,' says Ellen. 'But it might be that we have so little information on this group that this just hasn't been seen before.

'There aren't many True's beaked whales in museum collections, and I think overall it just shows how little we know about these species.'

Read more

  • Read the paper in full published in PeerJ.
  • Find out what ORCA is up to and how you can help.

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