Cause of death of Sowerby’s beaked whale in Wicklow Harbour Unknown

The reason a rare Sowerby’s Beaked Whale live stranded and died in Wicklow Harbour on 4 July 2020 is not known. Despite a full post-mortem being carried out at the Department of Agriculture, Food and the Marine laboratory facilities at Backweston, the cause of death could not be determined. Dr Simon Berrow of the Irish Whale and Dolphin Group, who were present at Wicklow Harbour throughout the event said “while frustrating, it is not unusual that despite carrying out a full post-mortem examination, we cannot establish why the animal stranded and died”.

The young, immature male measuring 4.3m in length was observed swimming erratically on the morning of 4th July and died that evening. It was recovered to Backweston the following day with help from Wicklow Sailing Club. The post-mortem was carried out by DAFM pathologist Margaret Wilson, at the state run lab. Dr Simon Berrow and Mags Daly of the IWDG, both who have considerable marine mammal pathology experience were also present to assist the vets.

The whale was not emaciated, it had moderate blubber thickness of 31-42mm and there was evidence of quite recent feeding, with fish bones present in its stomach and intestine. Parasitic infections in the liver, lung and stomachs were noted but were not severe enough to have compromised the animal, neither were multiple fluid filled cysts on the left teste or pox lesions on it skin.

Margaret Wilson of the Department of Agriculture, Food and Marine, Pathology Division said “we were delighted to be able to provide the facilities and expertise to carry out this post mortem investigation in collaboration with IWDG. While a definitive cause of death eludes us in this case, the extensive examinations carried out were very productive in terms of ruling out possible causes of death and expanding the knowledge of incidental lesions observed in this rarely post mortem examined species”.

Of interest but not thought to have contributed to its death was the partial impaction at the end of the intestine, caused by a bolus of fish bones and a piece of plastic measuring 95×30 mm. The plastic looked like it was from the corner of a hard plastic box.

Plastic found in anus of Sowerby’s beaked whale © Simon Berrow/IWDG

Dr Ferdia Marnell of the National Parks and Wildlife Service who commissioned the post-mortem examination said “there is great value in examining these type of cases, even if a definitive diagnosis is not reached, much can be ruled out and that is almost as valuable. In addition to which, we have recovered very useful samples for life history, diet analysis, genetics and contaminant burden analysis, and have yet another example highlighting the extent of marine debris hazards to even these pelagic offshore species”.

Plastic found in anus of Sowerby’s beaked whale © Simon Berrow/IWDG

During a post-mortem examination the whale is examined thoroughly externally for any lesions that may have contributed to its death or provide insight to what the whale may have been exposed too. Internal examination of all organs, including the brain also involves sampling for bacteriology, virology and histological examinations. This enables the pathologists to isolate any bacterial infections or unusual lesions within organs. Not all possible causes of death can be eliminated. With deep-diving species there is always concern about the role of acoustic trauma. To explore this as a potential causative factor involves examining the inner ear immediately on death and fixing and examining the organ, which involves specialist equipment and training which the team have not had. This was not possible in the case of the Wicklow whale which means we cannot exclude the role of acoustic trauma in the death of this whale.

The number of deep-diving offshore species stranding dead and alive on the Irish coast is growing. Increasing our knowledge of the life of these whalers and their pathology through carrying out thorough post-mortem examination such as occurred for the Wicklow whale is an important part of gaining new insights into some of our rarer and little understood whale species.


The post-mortem was carried out at the Department of Agriculture, Food and the Marine laboratory facilities at Backweston, Co Kildare by Margaret Wilson, with assistance from Brian Smyth and Paul Delaney. Simon Berrow, Mags Daly, Sibéal Regan and Meadhbh Quinn from IWDG were also present and Loraine Fay from the NPWS.

Sowerby’s Beaked Whale in BackWeston Regional Vet Lab, Co Kildare

Sowerby’s beaked whale stranding in Wicklow Harbour – July 4th

5 July 2010

On the 4th of July 2020, the IWDG were alerted to the presence of a “dolphin or whale” swimming in Wicklow harbour by Eoin Byrne. After sending a short video via WhatsApp it was clear this was a beaked whale. Beaked whales are offshore deep-diving species, and so it is highly unusual to see them in coastal waters let alone in a harbour setting. Our local members and volunteers quickly arrived on scene and were able to identify the animal as a male Sowerby’s beaked whale, due to the presence of triangular teeth mid-way along each lower jaw.

More information about this species may be found here at  There is little known about beaked whales, and much of the information we have so far has come from stranding records. What we do know is that they are normally found far offshore, have been known to dive to depths of over 1500m and are extremely vulnerable to acoustic trauma. A recent acoustic study ( regularly detected Sowerby’s beaked on the shelf edge, especially along the north-western slopes.

Upon arrival at Wicklow Harbour, our experienced IWDG marine mammal biologists visually assessed the health of the animal from the quay side. It was clearly not in good condition, appearing disorientated and experiencing difficulty moving and surfacing.  It had several bleeding cuts and abrasions on its rostrum, head and tail fin, which were presumably caused from repeatedly swimming into the concrete walls and other surfaces in the harbour.

Sowerby’s beaked whale in Wicklow Harbour © Hannah Keogh

A rapid breathing rate was also observed indicating that the animal was stressed and unwell. Therefore, it was not displaying the behaviour typical of a healthy animal. This, coupled with the fact that beaked whales are not known to live in the shallow Irish Sea, made it clear that this whale should not be refloated, and the difficult decision was taken to allow nature to take its course and for the whale to die naturally.

While euthanasia is often discussed when dealing with a live stranding, it is not always practical especially when dealing with a large animal in the water. There are human safety interests to consider as cetaceans are powerful animals even when severely debilitated. While not generally aggressive towards humans, a dying or injured animal may thrash around violently and potentially cause serious harm to a well-meaning onlooker or veterinary surgeon.  Pentabarbitone is a drug typically used for large animals in Ireland. However, to euthanase a whale as large as this would be challenging and few vets have the experience to be able to deliver in the field with cetaceans, particularly large whales. To be able to safely administer the dose required into the pericardium (heart) for a rapid response is challenging.  Also to consider are zoonoses, which are diseases or infections transmissible from animals to humans.

So unfortunately in these situations, while the empathetic instinct may be to jump in and attempt to “save the whale”, those actions may not be in the best interests or welfare of the animal and would more likely even cause it more unnecessary stress.

As the tide began to ebb, the animal moved direction and began to swim downriver towards the mouth of the harbour where it beached itself in the shallows. While distressing to watch, there was nothing further to be done other than to keep a respectful distance from the whale in its final moments.

IWDG members and members of Wicklow Sailing Club preparing to move the animal for retrieval © Meadhbh Quinn

The IWDG are extremely grateful to all the help received from members of the public in order to remove the whale respectfully and capably from the beach after it died.  A large coordinated effort was put in to move it onto a tarpaulin and float over to the Wicklow Sailing Club Slip, where a trailer and jeep organized by local farmer and sailor David Ryan was waiting to receive it.

The assembled team carefully moving the whale © Meadhbh Quinn

The IWDG have been drafting a Large Whale Stranding Response in order to formalize a rapid response effectively to respectfully respond to these situations in future. However in the absence of a formal protocol, the IWDG with its partners the Coastguard, NPWS, Regional Vet Labs and incredible local support felt that this was a ʺmodel” response to such an event and all the correct decisions were made.

Some important messages from this event are:

  • Every stranding is different, but the welfare of the cetacean is always the highest priority. If the animal appears to be sick or unwell, any attempt to refloat it may prolong its suffering and cause additional stress.
  • While onlookers may be well meaning, the best they can do is to keep their distance unless asked to assist. It is important to keep noise to a minimum and dogs under control.
  • We do not yet know what caused this offshore species to be found so far inland on the east coast and in such poor condition. It is known that beaked whales are vulnerable to acoustic trauma from anthropogenic (human) sources, among other issues. However, it is important to note that these are wild animals and die at sea of natural causes just like any other wild animal population. A necropsy will hopefully shed some light on the cause of death, but at this point we cannot speculate further.

IWDG have further information on how to deal with live stranding events in the form of our publication ‘Face to Face with a Beached Whale’ on our website (  We would urge anyone interested in learning more about stranding events and how to respond to read this document.

We would like to thank the Irish Coastguard for providing assistance on site as they have done so many times in the past during stranding events, for which we are very thankful. Also to the Wicklow Sailing Club members, Alphamarine Ltd, David Ryan and Eoin Byrne and all the members of the public who got involved. It would not have been possible to remove it for necropsy without your help.

IWDG marine mammal biologists Meadhbh Quinn and Hannah Keogh were on site yesterday monitoring the situation and coordinating the retrieval effort. Thank you also to the IWDG members assisting throughout the day, Liam Quinn, Darren Ellis and Irene Reidy.

By Meadhbh Quinn
IWDG Officer

For more information see