Why do whales beach themselves?

More than 100 pilot whales were freed after a pod stranded itself at Toby’s Inlet near Dunsborough on Friday, while 28 died.

Hundreds of locals turned out to help the rescue effort.

Murdoch University marine biologist and senior research associate Dr Joshua Smith said the stranding may have been due to the long, sloping seabed in the area confusing the whales.

“It’s something like two metres for every kilometre… a gradual two-metre increase every kilometre within the bay, which (is problematic) for these species that are typically found in deeper waters – that rely heavily on echolocation, which is basically their own little form of sonar,” he said.

“That’s how they image their environment, that’s how they navigate, they’re very highly acoustic animals, as most of the marine mammals are.”

Why do whales beach themselves?

Smith said there were several theories behind what caused pod strandings around the world, noting that many strandings in Australia happened in similar locations.

As well as a sudden shallowness in the water, he said, whales were highly social.

“If something is wrong, they’ll stick together and help each other out – they tend not to leave individuals to their own fate,” he said.

“The whales may have been protecting a sick individual, or they could have been sheltering from predators, namely orca, in the safety of the bay.

“But you would expect there to have been orca sightings if that were the case.”

He said another theory suggested whales stranded themselves in response to sonar noises from deep water vessels, but that was unlikely to be the case in shallow coastal waters.

Smith said would-be rescuers faced a tight 24-hour deadline to return beached animals to the ocean – though within 12 hours was preferred.

“Sadly, even if you get them back out to sea, they may still suffer internal organ failure and die,” he said.

“Whales evolved to live in the water, they are massive animals, with long-finned pilot whales weighing up to 2.5 tonnes each, and without buoyancy, basically their internal organs are being crushed.”

The aforementioned close social bonds among pods was also reflected in the reluctance of rescued whales to leave the still-beached behind.

Smith said re-beaching was “quite common”.

Are strandings growing more frequent and is climate change having an impact?

“It is important to remember that whales were stranding well before humans started impacting their environment,” Smith said.

“But it does seem that mass whale strandings might be happening more often.”

He said climate change was affecting whales but was unlikely to be the direct cause of a stranding.

“Although climate change is transforming our oceans, the impact is typically seen on a much larger spatial scale than individual stranding events,” he said.

“Warming seas, changes to cold water currents or upwellings, and impacts on the distribution and abundance of whales’ prey have the potential to change the distribution patterns of whales across the world and may lead them to unsuitable locations that could cause strandings.”