Posted by: orcaweb | May 24, 2017

Thoughts on an unfortunate sighting

It’s Sophie again, checking in from this past week aboard the Pont Aven.

Wednesday brought a misty crossing through Biscay. It definitely was atmospheric – you could easily imagine a ghost ship emerging from the fog! Despite the reduced visibility, the sea was very smooth and we still had several hundred dolphins spotted in total. Closer to Spain we also had a very close sighting of two Cuvier’s beaked whales – likely a mother and calf. Most beaked whales disappear very quickly, but these weren’t quite as quick and we got a longer chance to snap some photos. Due to some rainy conditions we were also lower down the ship (on deck six) so we felt much closer to them. Definitely a sighting that passengers appreciated.

Cuviers 31 edited. AndyG

Cuvier’s beaked whale mother (closer) and calf (further). Spotted within 200m of the Pont-Aven

Unfortunately, on closer inspection of the photos later, we were confronted with a saddening sight. While the calf seemed to be in a good body condition, the mother appeared emaciated. We can only hypothesise why this is the case. Our minds immediately went to an anthropogenic cause, was it a stomach full of plastic that is so often the case with marine wildlife? Has something happened to the squid that they feed on? It could simply be that she was sick, or old, and that prevented her feeding. However, her calf looked in a healthy body condition, so we wondered if the calf was perhaps part of the reason.

Cuviers44 edited, AndyG

Note her extremely poor body condition and protruding bones, that shouldn’t be visible in a healthy whale

Here’s an idea. Cuvier’s beaked whales are a deep diving species, reaching depths deeper than the sperm whales, and are less studied than sperm whales as well. We know in sperm whales that the calves cannot handle the extremes of diving deep as the adults do, so to allow the whale mothers to feed, the mothers will form crèches, taking turns staying at the surface with the calves. This is an example of alloparental care, seen in many social mammals. This allows the adult whales to feed at depth without leaving their calf alone and vulnerable at the surface.

Now extrapolate this to the beaked whales we saw. Not a huge amount is known about the social intricacies of beaked whales, but they are recorded in small groups, as well as alone. If this mother doesn’t have a family group for support, is she unwilling to dive to great depths to feed and leave her calf untended? Many mammals will nurse their young even as their body condition deteriorates, so the offspring will still be plump and healthy as the mother starves. A possible explanation perhaps?

However, let me emphasise that this is just speculation, and there are a number of explanations that could be the answer. This highlights why research is so important. We don’t know the reason why, we don’t know whether it is directly or indirectly caused by human action, or a natural but unfortunate occurrence. Without knowing what the problem is, we can’t hope to offer a solution. We can’t protect cetaceans without being equipped with understanding them.

Cuvier's emaciated-nursing2, May17, AndyG.jpg

The sighting was brief but the impact was not. We desperately hope that she is faring better.

If you are interested in participating in ORCA’s research, and would like to join our teams surveying for marine mammals all around Europe and the adjoining waters, do consider becoming a marine mammal surveyor.  It’s a one day training course and then you can start volunteering on a variety of different routes. For information click here.

In an effort to end on a lighter note, we have seen a fair few more sunfish. We have now seen ten so far, I’m keeping count! I love these fish. Last week Heather covered some of their biology. But when you see them, they’re so funny looking, waggling their fins at the surface. Even when I’m feeling down they cheer me up. I’ve started a light-hearted competition to see which wildlife officer can see the most sunfish by the end of the season. With still the whole of June to go it’s anyone’s game.

Stay tuned for more news from the Pont-Aven!


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