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Sowerby's beaked whale

25 September 2013

On Thursday 12 September, a Sowerby’s beaked whale adult and calf became stranded in the shallow waters of Village Bay, Hirta.  The 5m long adult female and 2m long calf were seen in distress just before 11am.  With so few people on island that could help we had to prioritise which animal to attend to first.   Kevin and I, with assistance from QinetiQ, contractors and a visitor to the island, immediately attempted to refloat the adult but, despite our quick response, we were unable to successfully move her before she died.  Whale - Attempting to refloat the whale (Photo: Doug Patterson)Whale - Adult female

 

While we were concentrating on refloating the adult whale, the calf freed itself without assistance but then stranded itself further along the shore.  After a few minutes it freed itself from this position and was last seen swimming out of the bay. Unfortunately, when I examined the mother, it became obvious she was lactating which suggests the calf was still dependent and unlikely to survive on its own.                                                                       

   Whale - Lactating

Teats inside mammary slits either side of the anal vent.













The Sowerby’s beaked whale (Mesoplodon bidens) is a small species (about 5m long) with males slightly larger than females.  The rounded bump at the front of the head is called the melon. This and other features such as a long slender beak, groove on the lower jaw and fin 'pocket'  all help with the identification of this species.  Only the adult males have erupted teeth or tusks half way along the lower jaw.   Individuals are usually heavily scarred but scarring is worse in males.  This female also had circular marks on her skin which are made by the Cookiecutter shark.

Whale - Head showing characteristic features

 










 

 

Whale - Head and fin

 

 

Lots of small scars and a pocket behind the fin that helps to streamline the animal.










Whale - Scar from a Coonkie Cutter shark





Scar from a cookiecutter shark.  The name 'cookiecutter' refers to the sharks feeding habit of gouging round plugs of flesh out of larger animals.















The species is thought to inhabit the deep offshore water in the North Atlantic ocean. It is shy and rarely seen at sea as it is thought to avoid ships, but there have been around 60 records of strandings around the British Isles in the last 24 years. Some of these have been from the North Sea, where the whales are believed to have become trapped in shallow water, but the strandings on the West coast have mostly been close to the deep water of the Continental shelf as at St Kilda.Whale -  distribution


The incident at St Kilda was immediately reported to Nick Davison, Coordinator of the Scottish Marine Animal Stranding Scheme (SMASS) based at the Scotland’s Rural College.  Nick said that “almost all we know about this species comes from examining stranded animals so it is vitally important to perform post mortem examinations on these animals when possible. Not only can we try and establish a cause of death but also gain insights into their life histories.”

 

I offered to take samples from the female and was given a comprehensive set of instructions (!) but due to the timing of the stranding, we were able to get the necessary permission for Nick to travel to St Kilda the following day.  Then it dawned on us that he would arrive at high tide and would have no access to the whale. Disaster.  Once again, QinetiQ lent a hand, or rather a CASE, to solve the problem and the whale was carefully transferred from the rocks to the slipway. Whale - Carefully moved by the CASE

 

The photos that follow were taken during the post-mortem exam. I debated whether to include these images in my diary entry as they are quite graphic.  However, I have chosen a specific few to illustrate some key points and include them for educational value rather than to shock. If you’re squeamish, look away now…..

 

 

(scroll down)

 

 

 

 



 


Whale - Measuring the blubber

Nick took samples of skin, blubber and muscle for analysis back at the lab. 


He also measured how thick the blubber layer was at three points along the midline of the whale. The values can then be used together to assess condition.

 









Whale - Nick Davison and Gina Prior performing post-mortem

Nick opened up the body cavity of the whale as he needed to inspect the internal organs and take samples from the heart, lungs, liver, kidneys, spleen and ovaries.  The liver showed some discolouration and there was slight redness in the uterus but most of the organs appeared to look healthy.


















 

 

Whale - otolith


Beaked whales feed predominantly on squid, although they also take fish. Upon examination of the three stomachs, Nick expected to find squid beaks but instead found these white structures.  They are otoliths, or the ear bones of fish, which have unique structures. This means Nick will be able to identify the type and age of fish the whale recently ate.









 


Whale - Parasitic wormThe stomach also contained these parasitic worms (which were still alive!). Apparently, they are common and Nick didn't think this was a particularly heavy parasite load and shouldn't have had much of an impact on the overall health of the whale.








 



 

Whale - Layrnx, commonly called the Goose beakDuring the post mortem, Nick examined many internal structures and showed us this curious thing.  It is actually the larynx but due to the structure is commonly called the 'Goose Beak'. 

It's an amazing adaptation to living underwater that is designed to keep everything but air out of the lungs (in humans, the respiratory tract and mouth cavity are shared. In cetaceans the respiratory tract is completely separated from the mouth cavity by the goose beak - this prevents anything 'going down the wrong way', a sensation I'm sure most of us have experienced before!)




 





Whale - Blood clot in the brain


Lastly, the brain was examined and a blood clot was found.  It is not clear yet whether this was a possible cause of the stranding or occurred as a result of the animal struggling once it was onshore.  Nick will run various analyses and tests back at the lab and the information he gathers will be pieced together to determine a possible/probable cause of death.





















These couple of days on island really were very dramatic but there was an overwhelming feeling of sadness over the loss of such an enigmatic creature, particularly because the calf was left orphaned.  However, I have to look for the positives and take comfort knowing that the post mortem provided a rare opportunity to learn more about an animal that is extremely difficult to    study in the wild.                                                        

                                                                                                                                     

Whale - Eye

It's almost as if she shed a final tear






















 





Gina



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