The beaked whales (Family: Ziphiidae) are a mysterious group of deep diving whales consisting of at least 20 species. Little is known about many of these species since they rarely visit shallow waters and are usually feeding on deep sea squid off the edge of continental shelves or close to other bottom features such as seamounts and canyons. However, since August a number of beaked whale strandings have occurred including the relatively well known northern bottlenose whale (Hyperoodon ampullatus) and Sowerby’s beaked whale (Mesoplodon bidens).
Northern bottlenose whales were heavily hunted until 1973 and the species has been recovering since. Current threats are thought to rise from acoustic disturbance since like other beaked whales, they are particularly vulnerable to mid frequency active sonar produced by the military to detect submarines. These animals are endemic to the North Atlantic Ocean, favouring colder and deeper waters of up to 1000 metres depth. Some make migratory movements southwards from the Norwegian Sea turning west past the Northern Isles and then south into the North Atlantic. One theory is that individuals somehow become disorientated and lose their way during this migration and this is the reason why they are sometimes seen in shallow coastal waters. However, a more likely scenario is that they follow the movements of their prey which are well known to exhibit seasonal mass migrations in late summer or autumn. Once reaching shallow waters, the whales are at risk of dehydration and starvation if their food source no longer is available which tends to be the case. If the whales enter very shallow water, this can also cause internal damage to the whale, and in most cases they are unlikely to survive.
This summer has seen five stranding events on the British coastline of this species since August. The first of the summer occurred in Cromarty, Northeast Scotland, where three individuals were seen in very shallow water. Two of these animals were euthanased but it was not known what happened to the third larger whale. It wasn’t until September that the next bottlenose whale showed up, this time off Bournemouth, Dorset. The whale (nicknamed Gilbert) was originally seen on the 12th and was spotted daily for the next few days. Sadly on the 21st the animal washed up dead, and post mortem results showed that the animal had not fed for some time. Also on the 21st, a juvenile northern bottlenose whale surprised onlookers up the River Clyde near Glasgow. It did not appear to be strong and after two days the animal disappeared. A series of west coast strandings continued when at the beginning of October yet another whale was found alive in Loch Eil, near Fort William and was encouraged to head out to deeper water by using killer whale and man made sounds! However, such attempts were unsuccessful and this whale also came to a sad end and was found dead a couple of weeks later. The most recent event was in Prestatyn, North Wales where another animal was found dead on the beach on Saturday 10th October. There had been no reports of the animal alive beforehand.
There have also been a number of strandings recently of the lesser known species, Sowerby’s beaked whale, Mesoplodon bidens which is rarely seen at sea. The first live stranded at Blakeney Point in Norfolk in August and was successfully refloated. Since then there have been a number of strandings across the North Sea. In Germany, one animal live stranded and was refloated at Busum on the 31st August. One week later however, an animal washed up off Minsener Oog which was possibly the same animal. On the 4th October another individual live stranded in Hoek van Holland, the Netherlands, and again was refloated. Sowerby’s beaked whales inhabit the North Atlantic with a distribution that ranges from Newfoundland to the Norwegian Sea in the north to Madeira and the Azores in the south. They seem to prefer deeper waters and most records in British waters have come from strandings. Some animals are known to strand in the North Sea, particularly in August and September. Reasons for these strandings are unknown but similar to northern bottlenose whale, may relate to movements into unfamiliar territory following squid prey.
For both species, this is the peak time of year that these animals are observed in British waters and tend to strand. However, these latter events are relatively high compared to normal. Although some are suggesting that military activities could be the cause the sudden series of bottlenose whale strandings on the west coast of the UK or for the North Sea strandings of Sowerby’s, at the moment there is no evidence to suggest this is the case.