In the last month, sperm whales have been showing up stranded on the shores of the North Sea. First, a dozen whales washed up on the Wadden Islands off the coast of Germany and the Netherlands. Now another group of five young males were found dead on England's east coast, reports Patrick Barkham for The Guardian.
The North Sea shores sees roughly six strandings each year, reports Barkham. So the recent rash of beached whales is concerning.
Whales can be driven to shallow waters where they strand and die for a number of reasons. Individuals may already be sick or dead when they beach. But mass strandings typically have a few other potential causes.
Toxins released by algae can work their way into the food web, which can distress and sicken whales. That's the explanation behind some recent events as well as an ancient mass stranding that happened between six and nine million years ago. Sound from ships and submarines, especially high-powered sonar, can also confuse the marine mammals, sending them ashore instead of out into the deep.
The cause behind these recent strandings, however, isn't yet clear, reports David Leveille for PRI.org. Toxins, a noisy ocean and injury are all causes that the scientists are keeping in mind as they investigate the sperm whales, says Andrew Brownlow from the Scottish Marine Animal Stranding Scheme. He's joined a group of veterinarians and scientists performing animal autopsies, called necropsies, on the whales, Leveille writes.
But the whales might have just gone to the wrong place at the wrong time. Brownlow tells PRI.org:
It’s a really bad place for these animals to be. Fundamentally it’s too shallow, around 150 feet deep, often shallower than that. This is a species that exists off of deep ocean trenches, dives as deep as 6,000 feet down to be able to forage. They navigate, communicate using acoustic clicks and we think in this very shallow environment that’s got very acoustically absorbing material like lots of sand and silt, they can’t navigate or communicate very well.
So far the necropsies have shown that the whales didn't have injuries that would have come from a collision with a ship. But rather, the whales were foraging. Whales found in the Netherlands had squid beaks and monkfish bones in their intestines, Barkham reports for The Guardian.
Once a whale beaches, if they are still alive, they won't be for long. Their enormous weight—sperm whales can grow to 35 to 45 tons—crushes their internal organs and damages their muscles, reports Sam Wong for New Scientist. Damaged muscle tissue releases the protein myoglobin, which is toxic to the kidneys. Along with dehydration, kidney damage often kills stranded whales.
Even if people reach a beached whale within an hour, before their kidneys become too damaged, pushing a creature as large as a bus is a difficult maneuver. And it won't necessarily be successful.
When 45 pilot whales stranded on Cape Cod in 2002, they were pushed out into the ocean. The next day, the pod beached again.
Euthanasia is the kindest option, according to Adam Grogan of the U.K.'s Royal Society for the Prevention of Cruelty to Animals, reports Michale Marshall for New Scientist. But sperm whales are simply too large to help those still alive when they beach.
"We don’t have access to sufficient volumes of drugs and we don’t have access to more physical means of euthanasia," Rob Deaville, of the Institute of Zoology in London, tells Wong. "At the moment all that can be done is to let nature take its course."