Scientists surprised to find salmonella in autopsies of whales that perished in mass strandings

When dozens of pilot whales died in two separate mass stranding events off the WA coast over the past 16 months, scientists from the Department of Biodiversity Conservation and Attractions (DBCA) were determined to find out the cause.

Last July, 97 pilot whales died at Cheynes Beach near Albany, and a further 31 perished at Toby Inlet off Dunsborough in April this year.

Marine scientists took swabs, blood samples and even removed the heads off some of the whales for CT scanning in the search for answers about the mass deaths.

"We're looking for firstly disease or to be able to exclude diseases," Dr Holly Raudino, marine scientist at DBCA, told Nadia Mitsopoulos on ABC Radio Perth.

"Particularly those [diseases] that are infectious to people, things like avian influenza, brucella and also something called cetacean morbillivirus, which isn't contagious to people but which whales and dolphins can suffer from," she said.

Tests excluded those diseases but did show up something surprising — salmonella.

"It initially showed up in the Cheynes Beach [Albany] stranding in multiple individuals," she said.

"We did a follow-up with the more recent Toby Inlet [Dunsborough] stranding and again, this has shown up and the reason that it is interesting and surprising is it hasn't really been detected before.

"We're just trying to work out whether it could have contributed to the stranding or not."

She said there was no record of salmonella being detected in pilot whales previously.

Navigation difficulty ruled out

As well as testing for diseases, the team also took on the logistical challenge of manoeuvring the heads of three of the whales into a CT scanner to understand if there were any issues with the whales' ears and disruption to their sonar abilities that could have led them off-course.

"So far, we haven't been able to detect any kind of catastrophic injuries to their ear parts, things like holes or perforations," Dr Raudino said.

She said hearing damage could be discounted as the cause of the two recent WA strandings.

"It is something that has caused strandings elsewhere around the world, however," she said.

"What we see is that it's different reasons for different strandings.

Strandings will continue

The team are also investigating the behaviour of the whales prior to the strandings, to see if that holds any clues.

"In the case of Cheynes Beach, we were very fortunate that several people got footage of the whales before they stranded, which is actually quite unusual," Dr Raudino said.

"Often we don't know about it until they land on the beach and they're reported by the public.

"So we are looking at that behaviour and trying to compare it to the behaviour of free-ranging pilot whales to see if there's any differences there, anything that could help us in our response or early intervention."

While Dr Raudino said the scientists didn't have a definitive answer, they are determined to keep working to try and understand why the mass strandings occur.

"We just keep looking. There's no end to it really," Dr Raudino said.

"This has been going on for thousands of years. It's not new. And it's definitely going to continue on into the future."