Cuvier's Beaked Whales UME- a Conservation Issue

30th Oct 2018

30 October 2018

The spate of beaked whale strandings reported to the IWDG has finished. There is little to report regarding the UME. The Irish government is providing support to the UK investigation and IWDG have supplied the few tissue samples we have from four stranded beaked whales to the Natural History Museum of Denmark, Section for Evolutionary Genomics at the University of Copenhagenin Denmark who host the largest collection of beaked whales samples in Europe to explore if the stranded whales were related andcould have been affected at the same time, The IWDG will also prtovide data for drift modelling to explore the offshore origin of these carcasses in Ireland and Scotland.

11 October 2018

As the number of reports of stranded beaked whales seems to have come to an end, maybe a reflection on the significance of this biggest Unusual Mortality Event (UME) of beaked whales anywhere in the world is appropriate. We know very little about any species of beaked whale in the NE Atlantic but what we do know is that they are not abundant and this mortality could be of conservation concern and not just a welfare issue. Recent estimates of Cuvier's beaked whale abundance from visual surveys in the NE Atlantic by Emer Rogan and colleagues (Rogan et al. 2017) in  the journal Deep Sea Research II suggested around 2,286 (95% CI 942-5,552) Cuvier's occurred in an area of 3 million km2. Now this is likely to be an understimate as beaked whales are very diffiult to see, but it certainly demonstrates they are not an abundant species. Estimates for Sowerby's beaked whales were higher (3,518 (95% CI 1570-7883) and yet most whales in this UME were Cuvier's. 

Under the ObSERVE Acoustic project ( detections of Cuvier's and Sowerby's beaked whales off the western seaboard of Ireland were more frequent than expected but this monitoring method cannot estimate abundance. Sowerby's beaked whales were more associated with canyon systems and Cuvier's likely to be more offshore in deeper waters ( 

Between Ireland, Scotland and Iceland around 80 Cuvier's beaked whale strandings have been reported. If we use the figure from French studies of the proportion of bycaught dolphins that make landfall and are recorded by stranding schemes (8%) then up to 1,000 individual whales may have died. Indeed the % recorded stranded of those dying could be much lower as Cuvier's are distributed much further offshore than the dolphins bycaught in the French study and more whales may sink at sea and not make landfall. So if Cuvier's only occur in their low thousands and hundreds may have died throught this UME, then we have a srious conservation issue, as this would have major impacts at population level. Of course these figures are open to much criticism, but it does demonstrate the potential seriousness of this UME. 

So what is happening? The UK government has launched an official investigation into the potential cause of this UME and the Irish government have said they will fully co-operate with it. The Icelandic goverment have also expressed concern so at least at senior government level there has been an appropriate response. We do know that of all the beaked whales, Cuvier's are the most sensitive to active sonar produced by some navies and mass stranding events have in the past been associated with naval exercises in the Atlantic and Pacific Oceans. We hope both European and international navies will also co-operate with this investigation; not so we can point fingers or throw stones but to avoid such a catastrophc event happening again. 

Dr Simon Berrow


Cuviers beaked whale off western Ireland © Enda McKeogh

29th September 2018

As reports of stranded beaked whales in Ireland and Scotland are finally dwindling we can now clearly see how disastrous this unprecedented event has been for Cuvier's beaked whales in our offshore waters. Records for Ireland for August and September 2018 stand at 23 Cuvier's beaked whales, 2 Sowerby's beaked whales, 2 Northern bottlenosed whales and 3 unidentified beaked whales. These are shocking figures and nothing like this has ever been recorded in Ireland before. What makes this whole event even more shocking is that at the same time, 45 Cuvier's beaked whales and 1 unidentified beaked whale washed up dead in western Scotland. Investigations are continuing to see if the cause(s) of this event can be established.


7th September 2018

After a number of emails to the Deptartments of Defence and Foreign Affairs, the Tánaiste and Minister of Foreign Affairs, Simon Coveney has "instructed his Department, in consultation with the National Parks and Wildlife Service, to initiate discussions regarding the large number of stranded Cuvier's beaked whales with the UK authorities". He states that he shares the concerns expressed by the Irish Whale and Dolphin Group and "thanks the IWDG for bringing this to our attention". The Department also stated it would be pleased to update us once such discussions have been finalised.

The number of Cuvier's beaked whales stranded on the Irish coast continues to rise and now stands at 19 and at least 16 in Scotland which has made it the largest UME (unusual mass stranding event) of beaked whales recorded in the stranding history in the UK and Ireland. The UK have recently stated they will launch an investigation.  Unfortunately the condition of the stranded individuals precludes post-mortem examination to assess cause of death but drift modelling to identify their provinance and discussions with the British Navy and NATO should be included in this investigation. 

The IWDG welcome the Departments response and look forward to hearing from them.


26th August 2018

Cuvier's Beaked Whales Ziphius cavirostris appear to be one of the more common beaked whale species but are seldom seen alive, with most information about them found by examining stranded animals. They live in deep water offshore, typically around deepwater canyons near the edge of the continental shelf and regularly dive for 20-40 minutes following a series of breaths at the surface. They are thought to be the deepest diving of the whales and in 2014 one animal was tracked to a depth of 2,992 metres with 138 minutes between breaths!

Between 3 August and 22 August 2018 a minimum of 16 Cuvier's beaked whales were found washed up dead on the Irish coast (minimum as it excludes animals reported which may have been already recorded, carcasses washed ashore unreported and carcasses which may have sunk at sea before washing ashore). During the same period, at least 13 were found in Scotland and 2 in Iceland. Previous studies have suggested that only a small number of dead animals actually get washed ashore and recorded, so the number of dead animals may be significantly higher.

The collage shows some of the photos of 16 strandings sent to IWDG by members of the public. Nothing on this scale has been recorded for this species in Ireland before although it is worrying that there was 11 recorded strandings of this Cuvier's beaked whales in Ireland over several months in late 2014 and 2015. In previous years, annual strandings for this species would typically have been 0 - 3 for an entire year. No cause of death has been established for any of these animals, mainly due to the fact that all washed ashore in poor or very poor condition, so all we are left with is speculation. The Irish strandings were recorded in Galway (3), Mayo (5), Sligo (3) and Donegal (5) and the condition of the carcasses suggested all may have died around the same time. This makes causes such as disease, plastic ingestion etc seem unlikely as these would tend to be spread out over a longer time period and perhaps geographical range. The behaviour and distribution of this species makes large scale fisheries interaction also seem unlikely.

While we can't say for sure, we do know from events around the world that beaked whales are susceptible to death or injury directly (temporary/permanent hearing damage) or indirectly (gas embolism - the 'bends' possibly due to a drastic change in behaviour) due to extremely loud man-made oceanographic noise such as that produced by low and mid frequency naval sonar and certain types of acoustic survey used to examine the sea floor and below. Mass strandings of beaked whales coincidental with naval exercises have been recorded in Greece, the Canaries and the Bahamas (The Irish navy does not use these types of sonar). While no definite cause has been established, this needs to be recognised as an unusual mass stranding event (UME) in an effort to identify the cause(s) and perhaps prevent a future re occurrence.

Mick O'Connell

IWDG Strandings Officer

You are welcome to share or use information and articles from this website but please reference the source and acknowledge the IWDG.