In an unusual case of déjà vu, a group of about 230 pilot whales stranded on Tasmania’s west coast on Wednesday (September 21), exactly two years after another group of pilot whales were stranded on and near the same beach.
The harrowing moments of the stranding could very well have been a coincidence, Rob Deville, project manager for the London-based Cetacean Stranding Research Program (CSIP), told Live Science. A number of factors can cause cetaceans — marine mammals such as whales and dolphins — to run aground, and it’s unclear at this point what factors contributed to this particular incident, he said.
“These events are obviously terribly unfortunate and terribly sad, but there is a historical precedent for them,” Deville added. “Unfortunately, there are strandings and strandings of pilot whales all over the world,” and Australia is a hot spot for such events, he said.
About 200 pilot whales (Globicephala) still died during the last landing in Tasmania, and their corpses may provide clues as to why the animals ended up ashore. The Tasmanian Department of Natural Resources and Environment (NRE Tas) will carry out a post-mortem examination of the dead animals, but “what caused the whale to strand is unknown at this time”, the department said in a statement. statement (opens in a new tab). Even with an autopsy, the cause of the stranding “cannot be determined,” the department said.
“Unfortunately, we have a really high mortality rate in this particular location,” as most of the animals were stranded on Ocean Beach, a long stretch of coastline exposed to rough surf, Brendan Clarke, NRE Tas officer and incident controller for the long-running event, said to journalists at a briefing for the local press on Thursday (September 22). Only a few animals were found stranded in nearby Macquarie Harbour, on a sand flat, This is reported by NRE Tas (opens in a new tab).
In the previous mass stranding in 2020, many pilot whales washed ashore in the mouth of Macquarie Harbour, “so they were actually in much more protected waters”, Clarke said.
About 470 long-winged pilots were involved in that previous stranding (Globicephala melas), which are actually a large species of dolphin, This was previously reported by Live Science. About 30 of the animals washed up on Ocean Beach, and more than 200 more were found on the sandbars located directly at the entrance to Macquarie Harbor – a shallow, narrow channel known as “The gates of hell (opens in a new tab).” About 200 more pilot whales were found further south, in harbor coves, This is reported by the Sydney Morning Herald (opens in a new tab) at that time.
In 2020, rescue teams were able to “float” again and release about 111 pilot whales back into deep water, This is reported by NBC (opens in a new tab). Rescuers were able to release 32 pilot whales back into the ocean this week and plan to rescue three more on Friday morning (September 23), NRE Tas reports. The other three whales were initially inaccessible due to high tides.
Ocean Beach remains closed to the public as the stranding response team continues rescue efforts, examines the dead whales and prepares the carcasses for disposal, which involves working with local aquaculture companies to pull the dead pilot whales ashore and put them in deep water.
While the response team deals with the immediate aftermath of the stranding, the question of why the pilot whales washed ashore is still unanswered.
Generally, “these are the most social species that get planted the most,” Deville said. Pilot whales — called “pilots” because they follow each other in a line — are known to form strong social bonds, he said. Evidence suggests that in some cases, mass strandings can occur because one pod member becomes sick or injured and becomes stranded, and the rest of the pods follow suit. In these cases, an injured or sick cetacean may end up in the shallows after becoming disoriented or washed ashore by the current.
On the subject: Nearly 30 pilot whales die after mass stranding in New Zealand
Evidence also suggests that echolocation by whales and dolphins doesn’t work as well in shallow coastal waters as it does in the deep ocean, Deville said. Therefore, if these animals venture into shallow water while chasing prey or another pod member, they may not be able to return to the safety of deeper waters.
Tasmania’s west coast lies near the “shelf edge”, beyond which the water deepens and marine mammals often forage, said Chris Carlyan, a wildlife biologist with the NRE Tas Marine Conservation Programme. ABC News (opens in a new tab). Examining the stomach contents of dead pilot whales can reveal whether the whales hunted near-shore prey before stranding, Karlian said at a press briefing.
A post-mortem examination could also reveal whether any whales were sick, injured or exposed to some kind of toxin before the stranding, but “to be honest, we didn’t expect to find anything like that,” Karlian said. “These mass strandings are usually the result of accidental beaching, and it happens for a number of reasons.”
Sometimes those causes are related to human activity, Deville said. For example, noise pollutionincluding that caused by sonar and seismic, can disrupt the ability of cetaceans to navigate, frighten or even injure mammals, potentially increasing the risk of strandings, according to National Geographic (opens in a new tab).
Given all the factors that can lead to a crash, is there a way to prevent such events? “It’s like [a] The million-dollar question is what can we do to stop this in the future, given that we know this is a hot spot for mass landings?” Carlyan said at the briefing. At this point, that question doesn’t have a satisfactory answer, he said.
“We’ll continue to look at that and whether some new technology or new, new ideas can help in that regard, but we just don’t have that option up our sleeve at this point,” he said.
Originally published on Live Science.
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