As anyone who has had the pleasure of swimming with a whale will likely tell you, the experience is nothing short of surreal. As you hang in the water column, surrounded by a seemingly endless expanse of ocean, it can be truly humbling to see a creature more than a thousand times your size emerge from the ethereal blue and drift past. So impressive in size, yet so graceful in movement.
Cetacean stranding – or beaching, as it is also known – occurs when whales and dolphins strand themselves on land.
Many of us will never be fortunate enough to experience this sight up close. And although we may gawk in wonder at the whales and dolphins filmed in nature documentaries, we also see images of a far more disturbing nature. Around the world, Cetacean strandings occur daily, often catching the attention of news outlets and other media. Seeing these majestic creatures lying helpless and dying on the world’s beaches stirs the emotions and poses the ultimate question – why does it happen?
Cetacean stranding – or beaching, as it is also known – occurs when whales and dolphins strand themselves on land.1 It can happen both on an individual basis and a larger scale, with so-called ‘mass strandings’ involving hundreds of animals at a time. The largest on record occurred in the Chatham Islands of New Zealand in 1918, when as many as 1000 pilot whales perished on the coast. But despite extensive research into the subject, concrete proof as to the exact cause of these events remains frustratingly elusive.
The consensus among the scientific community is that a range of factors is to blame. Some of these factors are natural, such as disease, injury, predator escape and simple mis-navigation. Whales and dolphins are famous for their intelligence, with many species exhibiting complex social behaviours and living in close-knit family groups.
Pilot whales are a prime example. Growing up to 7 metres (23 feet) long, these playful creatures are large members of the dolphin family and generally travel in groups of up to twenty individuals. But they are also the most common species observed in mass-stranding events. This is because when one animal falls foul to disease or becomes badly injured, the other members of the group will stay in the vicinity of the animal or even try to help it. If the struggling individual ends up stranding, the entire group becomes vulnerable to suffering the same fate.
Unsurprisingly, however, the actions of humanity are also to blame. The Zoological Society of London’s Cetacean Strandings Investigation Programme (CSIP) has monitored strandings around the United Kingdom since 1990.2 3 In that time, 12,000 stranding events have been recorded, involving 22 different cetacean species. Of the 3,380 of these individuals to be examined, the leading cause of death (699 cases) was entanglement or by-catch. This finding is consistent with a 2016 study published in the Journal of Coastal Research, which analysed humpback whale strandings in Queensland, Australia.4 Over a period of 25 years, 214 stranding events were reported, with more than one third (37%) being attributed to entanglements with fishing gear and other human debris.
This is hardly surprising when you consider how rapidly the global fishing industry has increased since the turn of the century. Fishing nets and other equipment are frequently lost or thrown overboard, where they drift through the planet’s oceans, posing a considerable threat to large baleen whales in particular, who follow strict migration routes. While it’s possible in some cases for whales to free themselves, many suffer severe injuries, which can weaken them, inhibit mobility and eventually lead to strandings or fatalities.
Alongside this threat, cetaceans are also vulnerable to collisions with ships. Large species such as North Atlantic right whales are very slow-moving, meaning they are sometimes unable to get out of the way of passing vessels. When collisions occur, they cause massive injuries, with injured animals often ending up stricken on beaches.
It is not just the ships themselves that pose a problem. A growing body of evidence suggests that sonar and other forms of noise pollution can interfere with and confuse cetaceans. Several mass strandings of beaked whales have been attributed to sonar activity, including a 2002 incident in which 14 beaked whales stranded in the Canary Islands after a sizeable naval exercise. Cetaceans as a group are extremely sensitive to sounds, meaning loud, sudden noises can inhibit their ability to communicate, as well as frighten and disorientate them.
Although cetacean strandings have occurred throughout history, the impact of human activities is becoming more apparent as we learn more about these peculiar events. But with pollution levels in the ocean continuing to rise and no slow-down in the global fishing industry in sight, it is a fair assumption that cetacean strandings will continue to be a sight on our beaches for years to come.
Meynecke, J.O. and Meager, J.J., 2016. Understanding strandings: 25 years of humpback whale (Megaptera novaeangliae) strandings in Queensland, Australia. Journal of Coastal Research, (75), pp.897-901. ↩