TRANSCRIPT:
It was a heartbreaking scene: at least 28 long-finned pilot whales dying after beaching themselves at Toby Inlet near Dunsborough in Western Australia.
They were part of a larger group of approximately 160 pilot whales who became stranded.
Onlookers told the Nine Network they tried to push the mammals back out to sea, or hold them up so they could breathe.
"Our connection to the ocean is very deep and to me these are like our ancestors." (Cries)
"I've never experienced a live stranding like this before."
"I was about up to waste deep trying to keep them out because it was a bit rough; we were trying to dodge tails and stuff because they were very determined to come into the shallows."
It's the second such beaching incident in the last 12 months, with at least 90 pilot whales dying after becoming stranded on W-A's Cheynes beach in July 2023.
Pilot whales are known to inhabit Bremer Canyon, a very deep ocean area 70 kilometres off the WA coast.
But two strandings of the creatures in twelve months has raised new questions about why this keeps happening.
Joshua Smith is a senior associate researcher in the marine megafauna group at Murdoch University.
He says it's unusual for these creatures to be near the coast, because long-finned pilot whales are generally found offshore, in the deep open ocean.
"Basically, whenever you get an event like this, a mass stranding, of such a large number of whales, the natural question that everybody has is, is why is it actually occurring? You know, we've had stranding events for many, many decades. unfortunately, all the way around Australia. There do seem to be relatively, similar places, I guess, around Australia, where stranding events seem to occur ... These are the same similar sorts of, species that we saw mass stranding down in Cheynes beach in Albany just last year. And I guess in terms of the species themselves, they often occur in relatively large groups. Very seldom actually are they usually found in coastal areas."
While it's difficult to determine exactly why they were so close to shore, Dr Smith says the stranding could have to do with the location itself.
"It's an area that's actually saying a couple of stranding events in the past. And I guess kind of what's unique about these areas is really the relatively shallow waters that it has in the long, sloping seabeds, that we have. I think it's something like, two meters every kilometres is what we have is a gradual to increase every kilometre within the bay for these species that are typically found in, the deeper waters, I should say that they're a tooth whale and they rely heavily on echolocation, which is basically their own little form of sonar. That's how they image their environment. That's how they can navigate."
But in general, scientists aren't exactly sure of the root cause.
Dr Stuart Johnson is from the University of Melbourne.
"It's just difficult to collect data on whales. You know they are large marine mammals but the ocean is a really, really big place. So collecting evidence is quite difficult because you have to find the whales in the first place. You can't really do controlled experiments in the ocean. With a lot of other animals you might be able to do experiments in the lab; we can't do that for both logistical and ethical issues."
Researchers do have theories.
One is that it's possible that a matriarch in this particular population became sick and they've followed her into shallow waters.
Another ties into the impact of noise pollution.
Dr Smith says these are mammals that are highly acoustic and rely heavily on echolocation, using it to keep in social contact and communicate.
"And in shallow waters, it does become a little bit problematic in terms of what they have termed sonar termination. Now, we really don't know-- I guess I should say this, off the bat, unfortunately, whilst, mass strandings have been around for a while, we still haven't really been able to figure out exactly why that is."
Dr Johnston says many things can create noise pollution, including shipping traffic, natural resource extraction, construction activity off the coast, or any type of human activity happening under water.
"So it could be that it's a stress-type response. So, if you're sitting at home and someone starts a chainsaw up next to your window, it's probably a little bit stressful. And if that gets louder and louder, you may want to flee away from that. And if you flee without wondering where you're going, you could run into trouble. Alternatively, it could be disrupting their ability to talk to each other; they just can't hear each other over the noise. And yeah, echolocation for certain citation species; maybe they're not hearing that signal bouncing off the coastline correctly."
But he says it remains unclear what connection humans have with what's going on in the ocean.
"We know that these whales have evolved to exist in quiet ocean conditions, but over the last 100 years there's been more and more human activity in the oceans and that's changed things quite significantly. And we think that's impacting the whales' ability to communicate and navigate. Though as you say, there are quite a number of theories and it's very difficult to narrow down what exactly causes these mass stranding events. It's still very much an open question."
After the stranding at Toby Inlet, officials from the state's Department of Biodiversity, Conservation and Attractions began the grim task of removing the dead whales from the beach.
They also took measurements and samples.
Regional Wildlife Officer Pia Courtis says they're hoping those samples could finally provide some insight into the mystery of whale beachings.
"Every whale stranding is different and there's different circumstances and different situations. So it's hard to say. I mean I guess it's… we've learned some things from Cheynes beach (July 2023 whale stranding). So we've put them into play here. And yeah, it's hard to tell. It's a different location, but we'll try and take as many samples as we can to see if there's anything happening in the population."
