Earlier this week on New Zealand's remote Chatham Islands, 477 pilot whales died after getting stranded along two beaches in one of the larger beachings the country has seen.

Less than a month earlier, 230 whales found themselves stranded on the island of Tasmania in Australia, with rescuers able to save dozens of the marine mammals.

Grisly images from the recent spate of whale strandings have captured worldwide attention, and they have also highlighted just how hard it is for scientists and conservation experts to prevent such incidents.

Strandings happen all over the world, yet researchers don't know for sure why whales get beached.

Here's what to know about why whales get stranded and what can be done about it:

Scientists don't know why whale strandings occur, but they've got some ideas

Though experts don't understand for certain why whales end up stuck on land, they have some theories.

Whales — along with dolphins and porpoises — belong to a category of marine mammals known as cetaceans. Dolphins and certain whales travel in groups, and both have gotten stranded in large numbers.

Toothed whales, also known as Odontoceti, use echolocation to navigate underwater and communicate with each other.

According to Dr. Vanessa Pirotta, a wildlife scientist at Macquarie University in Sydney, some whales may get stranded due to a navigational mistake.

She told NPR that the recent stranding on the Chatham Islands could be attributable to the deep waters around the very remote land mass.

"It could be that these animals may have been fishing or transiting through the water and unfortunately came through a navigational hazard and ended up on the beach," Pirotta said.

Another explanation — what Pirotta calls "misadventure" — is that because pilot whales are highly social, they may simply follow a sick whale that ends up on the beach.

Other reasons whales may strand is because they're fleeing from predators, they're scared by a noise, they're injured or they're giving birth.

"The key point here is that any animal involved in a stranding does not want to be stranded," Pirotta said.

"There's a reason why it's happened, and we don't know why. Trying to work that out is still a massive mystery in the science world."

Whale strandings aren't preventable, but sometimes the animals can be saved

If the whales are still alive by the time 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 a beached whale with water is to cool it down, since whales lying out in the sun may overheat.

Whales stuck on land also don't have the buoyancy they experience while swimming through the water, and if they are beached the significant weight of their bodies can crush their organs.

That's why scientists may attempt to move whales back out to sea in a process called "re-floating."

But there are pitfalls to this strategy, too. Whales may have internal injuries that would kill them once they are returned to the ocean or they may get traumatized by the re-floating process, according to the International Whaling Commission.

Pirotta noted that some whales that are successfully re-floated may simply get stranded again.

In the recent event on the Chatham Islands, nearby sharks and a shortage of trained medics made re-floating impossible, and experts with the local rescue group Project Jonah euthanized the whales that survived the initial stranding.

Strandings make the news, but it's unclear if they're happening more frequently

Strandings occur all over the world, but it's often one or a few animals that get washed ashore rather than hundreds.

According to NOAA Fisheries, there were 7,320 confirmed strandings of cetaceans, sea lions and seals in the U.S. in 2018.

Globally there have been some high-profile strandings in recent years, including the deaths of 380 pilot whales off the coast of Tasmania in 2020.

It's unclear if the deadly events are becoming more frequent worldwide. But some research — including a report from the United Kingdom and a study in Chile — have shown a rise in the number of cetacean strandings.

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