Earlier this week, on New Zealand’s remote Chatham Islands, 477 pilot whales died after washing up along two beaches in one of the biggest strandings the country has ever seen.
Less than a month earlier, 230 whales ended up stranded on the island of Tasmania in Australia, with rescuers able to save dozens of marine mammals.
Grisly images of the recent spate of whale strandings have captured worldwide attention and also highlighted how difficult it is for scientists and conservation experts to prevent such incidents.
Strandings arrive all over the worldbut researchers don’t know for sure why the whales get stranded.
Here’s what to know about why whales get stranded and what can be done about it:
Scientists don’t know why whale strandings happen, but they have some ideas
Although experts don’t understand for sure why whales end up stranded on land, they do have a few theories.
Whales — along with dolphins and porpoises — belong to a class of marine mammals known as cetaceans. Dolphins and some whales travel in packs, and both have stranded in large numbers.
Toothed whales, also called Odontocetesuse echolocation to navigate underwater and communicate with each other.
According to Dr Vanessa Pirotta, a wildlife scientist at Macquarie University in Sydney, some whales can get stranded due to navigational error.
She told NPR that the recent stranding on the Chatham Islands could be attributed to the deep waters around the very remote landmass.
“These animals may have fished or transited through the water and unfortunately crossed a navigational hazard and ended up on the beach,” Pirotta said.
Another explanation – what Pirotta calls “misadventure” – is that because pilot whales are very social, they may simply follow a sick whale that ends up on the beach.
Other reasons why whales can run aground it is because they are fleeing from predators, they are afraid of a noise, they are injured or they give birth.
“The key point here is that any animal involved in stranding doesn’t want to be stranded,” Pirotta said.
“There’s a reason this happened, and we don’t know why. Trying to figure this out is still a huge mystery in the scientific world.”
Whale Strandings Can’t Be Prevented, But Sometimes Animals Can Be Saved
If the whales are still alive when they end up on the beach, there are some strategies scientists can use to try to save them.
As mammals, whales breathe air and can survive for a certain period on land. The reason you may see someone splashing water on a beached whale is to cool it, as whales lying in the sun can overheat.
Whales stuck on land also lack the buoyancy they experience when swimming in the water, and if stranded, the heavy weight of their bodies can crush their organs.
This is why scientists may attempt to bring whales back to sea in a process called “re-floating”.
But there are also pitfalls to this strategy. Whales may have internal injuries that would kill them once they return to the ocean or they may be traumatized by the refloating process, according to the International Whaling Commission.
Pirotta noted that some whales that are successfully released may simply be stranded again.
In the recent Chatham Islands event, nearby sharks and a shortage of qualified doctors made refloating impossible, and experts from the local rescue group Project Jonah euthanized the whales that survived the initial grounding.
Strandings are making headlines, but it’s unclear if they’re happening more frequently
Strandings happen all over the world, but it’s often one or a few animals that are stranded rather than hundreds.
According to NOAA Fisheries, there were 7,320 confirmed strandings cetaceans, sea lions and seals in the United States in 2018.
Globally, there have been high profile strandings in recent years, including the Death of 380 pilot whales off the coast of Tasmania in 2020.
It is not known whether deadly events are becoming more frequent in the world. But some research, including a report from the UK and a study in Chile — showed an increase in the number of cetacean strandings.