Experts baffled as rarely seen beaked whales involved in series of strandings

The Guardian

30-07-2025

A series of strandings of one of the world's deepest dwelling and most rarely seen types of whale in the last few days has left experts baffled over why they might have appeared in such numbers.
Beaked whales are used to deep ocean waters and are so rarely seen that some species have only ever been identified through dead specimens. But on 26 and 27 July there were reports from western Ireland, Orkney in Scotland and the Netherlands of these whales being stranded, raising concerns that human actions could be implicated in the animals' deaths.
'When you see these divers in the shallow North Sea, you know that it's going to be a grim end,' said Dr Jeroen Hoekendijk, a marine scientist and photographer who attended the scene of the Netherlands stranding on 26 July. A male and a female were beached between Heemskerk and Wijk aan Zee, north of The Hague, where the sloping shores of the southern North Sea are a notorious black spot for whale strandings.
'When SOS Dolfijn [the Dutch cetacean rescue team] arrived on the scene the two whales were thrashing wildly in the surf,' said Hoekendijk. 'They were obviously animals in distress.'
Although the whales were kept cool and wet with hoses, the male died soon after being found, and the second animal, a female, was euthanised to save it from further stress.
On 27 July two True's beaked whales, a mother and calf, were found stranded in North Mayo, Ireland, according to Dr Simon Berrow of Irish Whale and Dolphin Group. The female died and the calf swam off, but is 'unlikely to survive', Berrow said. On the same weekend in Papa Westray, Orkney, four northern bottlenose whales, also a species of beaked whale, were found dead, said Dr Andrew Brownlow of the University of Glasgow.
Brownlow and his colleagues from the Scottish Marine Stranding Scheme (SMASS) also attended last year's mass stranding of 77 pilot whales on Sanday, Orkney. 'July is a particularly bad month for strandings,' he told BBC Scotland.
There may be natural reasons for these incidents – there was a suggestion that the 2024 Sanday event was caused by the pilot whales being pursued by a pod of orcas. But the human-induced climate emergency is also causing warming waters that alter feeding habits throughout the marine food chain. And with seismic surveys for oil and naval sonar exercises also implicated in other beaked whale strandings (these types of underwater disturbance can cause diving whales to surface too quickly, thereby suffering decompression sickness) the impact of increased military activity is also a possible reason for these strandings.
Whereas other cetaceans – whales, dolphins or porpoises – can sometimes be refloated, beaked whales, possibly 100 miles (160km) or more from their natural environment, are already too stressed. 'They will not survive any attempt at a return since the animals won't be able to feed,' said Hoekendijk.
Reporting on initial findings from the weekend, Brownlow said: 'We found extensive liver pathology in the bottlenoses, possibly consistent with acute starvation.' He added that there may have been 'anthropogenic noise disturbance'.
SMASS and the University of Utrecht's strandings investigation team were quickly on the scenes, and were able to remove the carcasses for immediate necropsy. Their prompt action is especially important because evidence of any sonic disturbance that may have led to the whales' stranding can only be detected from swift examination of hair cells in the animal's inner ear. Once these have started to degrade, analysis becomes impossible.
Despite being large animals – up to 13 metres long – beaked whales, so called for their prominent snouts or beaks, are among the least known of all cetaceans. Diving so deep in the dark ocean, they rely on echo-location to navigate and to find their food. They live in a world of sound, which is why anthropogenic or human-created noise pollution has such a serious effect on them. They also hold the record for the deepest and the longest dives of any animal. Cuvier's beaked whales, bearing satellite tags, have been tracked off the coast of California at up to 3,000 metres in depth.