Whale experts all across the globe are still puzzling at the mass beaching of pilot whales in New Zealand that hit the headlines recently.
On the morning of February 10 2017 more than 416 pilot whales were discovered on Farewell Spit on New Zealand’s South Island.
By dawn three quarters of the whales were dead. An additional 240 whales stranded themselves late the next day. The total of 656 made this the second-largest whale stranding ever.
About 335 of the whales died. 200 re-floated themselves at high tide with help from human volunteers.
Cetacean stranding is an intriguing yet fairly common phenomenon as every year up to 2,000 animals beach themselves.
Most beached whales are toothed whales (Odontoceti), rather than baleen whales (Mysticeti). Toothed whales include the sperm whale, oceanic dolphins, killer whales, some beaked whales and two very similar species of pilot whale.
Toothed species share some characteristics which may explain why they beach. They live in deep waters in large, tightly knit groups. These tight social groupings are a major factor in mass beaching. If one animal gets into trouble, its distress calls may prompt the rest of the pod to follow and beach themselves alongside.
Many theories — some of them controversial — have been proposed to explain beaching, but the question still remains unresolved.
Some can be attributed to natural and environmental factors, such as rough weather, old age or infection, difficulty giving birth, hunting too close to shore, or navigation errors.
Some strandings may be caused by larger whales following smaller dolphins and porpoises into shallow coastal waters where the larger species may become trapped.
Old whales and those in poor health may find it difficult to keep up with their pod and may strand. Whales can suffer from a number of diseases that leave them weak and disorientated, or with impaired echolocation resulting in beaching.
Natural and man-made toxins can poison whales. Because they are at the top of the food chain, pollutants tend to accumulate in their blubber. Sadly many stranded whales have been found with large volumes of litter or plastic in their gut.
Whales get trapped and injured in fishing gear or are hit by passing vessels. Overfishing too can cause a shortage of food hence dependant calves and solitary older adults particularly may be malnourished.
Calving mothers will often seek out sheltered bays to give birth and if too close to shore or having problems giving birth they may strand.
When chasing prey whales may accidentally come ashore and, in a role reversal, they may also come too close to shore to avoid predators such as killer whales.
Gently shelving, sandy beaches may not reflect echolocation signals back to the whale, confusing them to believe they are in deeper water.
One contentious explanation is that military activity can interfere with whale’s echolocation systems and there is evidence that active sonar leads to beaching as do loud underwater explosions.
The low frequency active sonar (LFA sonar) used by the military to detect submarines is the loudest sound ever broadcast into the seas. At 240 decibels it is loud enough to kill whales and dolphins — for humans the death threshold is at around 185- 200 decibels.
The US Navy has plans to deploy LFA sonar across 80 per cent of the world oceans despite the fact that it has already caused mass stranding and deaths in areas where US and Nato forces have conducted exercises. The large and rapid pressure changes made by loud sonar cause haemorrhages.
The US Navy accepted blame when 17 cetaceans were killed in the Bahamas in 2000 during a sonar exercise — it was haemorrhages around the ears that killed the whales.
Over the past decade there had been a number of mass strandings of beaked whales in the Canary Islands and each time the Spanish Navy was conducting exercises — when there were no exercises there were no strandings.
History records some spectacularly large events. In 1918, approximately a thousand pilot whales stranded on the Chatham Islands off New Zealand, the largest whale stranding ever.
In 1985 about 450 pilot whales were stranded near Auckland, New Zealand and in 2015, 337 dead whales were discovered in a remote fjord in Patagonia, southern Chile.
A century ago in Britain we used to hunt pilot whales. In 1888 residents of Hoswick in Shetland drove around 340 pilot whales ashore. Local landowner John Bruce tried to claim the valuable whales for himself but in a famous case local crofters and fishermen took him to court and won.
We eventually gave up this barbaric practice but in the Faroe Islands pilot whales are still driven ashore and slaughtered today — 800-plus pilot whales are killed here every year.
Crowds of local people, many of them children, gather to watch this bloodthirsty spectacle as dozens of pilot whales are driven ashore by a flotilla of small boats.
Driven into the shallows they are killed by hunters wading into the water with long knives. This cruel hunt is known as a grindadrap, or grind.
Just last year a pod of pilot whales was sighted off the islands and 25 boats set out in pursuit. In the course of two hours, the men drove the whales ashore and of the 200 whales in the pod, 120 were slaughtered.
This whaling is an age-old tradition but a barbaric one. The Faroese, who are semi-autonomous from Denmark, insist what they are doing is legal and sustainable.
Others like the antiwhaling group Sea Shepherd think not and are trying to halt the hunts in the Danish courts.
Still today, in Britain and all around the globe, whales will continue to come ashore and crowds will flock to see these magnificent creatures close to.
These events may be tragic but they do not actually threaten the survival of any of the species involved. That doesn’t mean we shouldn’t try to understand them and do all we can to avoid these spectacular, sad tragedies.
This article first appeared in the Morning Star 24 February 2017.