The science is in on whether whales buried on beaches attract sharks
New research has debunked the theory that sharks are attracted to beaches where whales have been buried, but the science will face a public perception battle.
In September 2017, a 20-tonne dead whale was buried on a beach at Port Macquarie on the New South Wales mid-north coast; a week later it was exhumed when locals became concerned the decomposing carcass would attract sharks.
A research project completed in the two years since the incident has found those fears were largely unfounded.
The study, carried out at Southern Cross University's National Marine Science Centre in Coffs Harbour, concludes that — when done correctly — burying whale carcasses on beaches will not attract sharks.
Lead author of the study and Southern Cross University PhD student James Tucker said when he began his research two years ago, the belief was the opposite.
"The public perception at the time was that whale carcasses — even when they were buried on beaches — would attract sharks," he said.
"A lot of people said they would, a lot of people said they wouldn't, but it seems a majority, or at least the most vocal majority were saying that they would attract sharks and make beaches more dangerous effectively."
Burial is a viable option
The study, based on field trials using 360 kilograms of humpback whale flesh, found that the reach of decomposition plumes was less than 2.5 metres.
"Provided that certain conditions are met, it's very unlikely that those decomposition plumes will reach the ocean, where they're available for sharks to sense," Mr Tucker said.
Those conditions include ensuring the carcass burial site is above the groundwater table and high-tide mark.
"We also found that [the plumes] don't last very long at all, so what we think is happening is that carcasses that are buried in the sand are pretty much mummifying, so we're not seeing much decomposition product come off those carcasses," Mr Tucker said.
While the study found the risk of shark was minimal, it also acknowledged assumptions from the study site could not be generalised to all beaches — given conditions and groundwater presence can vary.
For that reason, the study concludes that certain conditions should be met when considering burying whale carcasses.
"The best thing to do is to have no water passing through — or a limited amount of water passing through — the burial site and bury the carcass far enough up the beach so that no very large spring tide is going to inundate it," Mr Tucker said.
"It's likely that provided certain conditions are met, burial is a safe option."
This whale was buried at Port Macquarie in 2017, before being exhumed a week later due to concerns it would attract sharks. Photo: NSW National Parks and Wildlife Service.
Review will decide the future of whale burial
There are no published best-practice guidelines on how to best deal with whale carcasses, but the Office of Environment and Heritage is reviewing its management practices, and the findings of this study are being taken into account.
"The Government is considering the next steps in the review process; in the interim the National Parks and Wildlife Service [NPWS] has taken steps to improve the coordination of response to incidents," a NPWS spokesperson said.
The review will also consider community concerns about shark attraction.
Fear influences public perception
The whale carcass burial and subsequent exhumation at Port Macquarie in 2017 was followed by a similar controversy less than a month later at South Ballina on the NSW north coast.
The Office of Environment and Heritage initially buried a dead baby humpback whale 150m from the shore, before a public outcry saw it dug up and moved to a waste management facility.
Ballina Mayor David Wright said people had grave concerns at the time, given the area already had experienced an unprecedented string of shark attacks in the previous 30 months.
He said despite the research, the public would take time to change its perception.
"Just burying it [a whale] on the beach, I don't think is an acceptable thing to do these days," Councillor Wright said.
He said that while the cost of moving a carcass was significant, it had to be weighed up against the cost of other factors, including loss of income for local businesses.
"You've got to be very cautious; if you bury a whale on a beach, and people know that, they won't go to that beach," Councillor Wright said.
"None of the tourist destinations want that to happen."
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