Why do whales become stranded?


March 23, 2018 17:09:07

More than 150 whales have stranded themselves in Western Australia’s Hamelin Bay.

Sadly, most the whales have now died, with rescuers in a race against time to move about 15 of the whales left alive out to see.

We got Curtin University marine mammal scientist Bec Wellard to explain a little bit more about why the stranding has happened.

Why did the whales become stranded?

The short version? We just don’t know.

Ms Wellard says whales strandings are complex events, in most cases the exact cause is unknown.

“One of the theories we do have … it could be a high risk area. The environment could be the cause of repeated strandings,” she said.

Other reasons include:

  • Man-made noise within the whale’s environment
  • An illness within the whale group
  • Naval activity
  • A salmon run

In this case, there wasn’t anyone there to witness the initial stranding, so we may never know the exact cause of the event.

Why did so many of them strand?

It’s because short-finned pilot whales — the species of whale that has stranded at Hamelin Bay – are incredibly social creatures with strong family bonds.

Here’s Ms Wellard:

“When one whale becomes stranded, the rest tend to follow.

“They’re highly vocal and they’ve got complex acoustic signalling within their social groups so that could be one of the reasons why they strand en masse.”

The official term for an event like this is a mass stranding.

Ms Wellard says mass stranding events almost always involved species of whales that live far off-shore and are deep divers.

Long and short-finned pilot whales are also the most common types of whales that end up in mass stranding.

Could the whales have been saved?

Maybe not according to Ms Wellard.

“Sometimes when you float these animals in large groups they will re-strand themselves if there are still animals on the beach,” she said.

Most likely the event happened overnight or very early in the morning, making the already difficult task of saving the stranded whales even harder.

Has this happened before?

Yep. Incredibly, it happened on the same date at the same location in 2009.

On that occasion more than 80 pilot whales and dolphins died in a mass stranding at Hamelin Bay.

On March 22 in 2015 — just one day earlier than the latest event — 20 whales became stranded in the South West town of Bunbury in 2015, which is just a few hundred kilometres north of Hamelin Bay.

The biggest mass stranding of whales in WA was in Dunsborough in August, 1996, when 320 long-finned pilot whales beached themselves.

Ms Wellard says there’s an area off New Zealand called Golden Bay where there are strandings involving pilot whales almost annually.

It’s known as a whale graveyard.






Source link

Leave a Reply

Your email address will not be published. Required fields are marked *