Whales have again stranded off the coast of Tasmania in large numbers, with rescuers doing their best to get the animals back to deeper waters.
It is estimated approx 230 pilot whales got into trouble in the shallows near Macquarie Headson the west coast – exactly two years since another stranding in the same place.
Wednesday’s event comes just two days after 14 young sperm whales were found dead on the coast of Tasmania’s King Island.
So why do these events keep happening and is there something about Tasmania’s topography that makes whales more susceptible to stranding?
Two strandings in one week ‘unusual’
In short, the cause of whale strandings can often be a mystery – and at this stage, that is the case with the situation unfolding at Ocean Beach.
With more information expected on Thursday, the Department of Natural Resources and Environment Tasmania (NRE Tas) said on Wednesday its rescue efforts would be guided by the “comprehensive Cetacean Incident Manual”, which had “undergoed extensive revision since the 2020 mass stranding”.
NRE Tas said marine animal experts would “assess the scene and situation to plan an appropriate response”, but offered no insight into what had caused this event.
Marine expert Vanessa Pirotta said it was the million-dollar question of why strandings occur.
“Whale strandings are a complete mystery,” said Dr. Pirotta, “but what’s really unusual here is that this is the second stranding this week.”
She said with pilot whales, which are very social animals, there were a few common theories about what leads them astray.
“So one can be misguided,” said Dr. Pirotta, adding that environmental factors could also potentially come into play.
“The fact that we’ve seen similar species at the same time in the same place that repeats in terms of strandings… might give some kind of indication that there might be something environmental here,” she said.
“The reality is we just don’t know at this point.”
Herd mentality a likely contributor
After working for the Tasmanian Environment Department in the 80s and 90s, retired vet David Obendorf has seen his fair share of whale strandings.
Although he has not been involved in this particular event, he said one factor that could play into the strandings was the species that was the “herding whale”.
“There are certain times of the year and places that tend to have a frequency of whaling,” said Dr. Obendorf.
He said the beach topography in Tasmania and tidal conditions could make an environment more susceptible to strandings, with both Tasmania and New Zealand well-known “hot spots”.
“All that happens if whales, through their echolocation, can’t navigate deeper water and get a confused echo signal.
“They can find themselves in shallow water and then send out distress calls… leading to a pod stranding. These animals, because of their size, become embedded in the sand by the time the tide is out and collapse into the sand.”
The next time the tide comes in, he said, the animals are unable to right themselves and may then drown from taking in seawater.
Tasmanian coast close to the sea shelf
While strandings of the magnitude seen in Macquarie Harbor in both 2022 and 2020 are rare events, strandings as a whole are not, Department of Natural Resources and Environment wildlife biologist Kris Carlyon stated.
He said it was Tasmania’s unique topography that made it something of a “whale trap”.
“Our coast is very close to the shelf edge where it drops off, and many of these species forage in deeper water beyond the shelf edge,” said Dr. Carlyon.
“Our bathymetry, the kind of coastal topography around Tasmania, is quite complex … so we’ve certainly seen mass strandings of pilot whales, of dolphins and sperm whales also on King Island before, and around north-west Tasmania.”
Teenagers looking for trouble?
When it comes to sperm whales — like those found stranded on King Island earlier this week — Dr. Carlyon again that a social element came into play.
“Sperma whales are really interesting. When the males get to about five, six years old, they tend to peel off the mother group,” he said.
“So they get thrown out of the group … they become a little more independent.
“But the young animals, before they’re big and sexually mature and can hold their own against the big breeding steers, they tend to hang out in groups … like groups of teenagers hanging around together.”
That’s why, he said, the common number of whales found at beaching pods tended to be between six and 20 animals.
“Often it’s just an accident.”
Sightings of free-swimming or beached whales and dolphins must be reported to 0427 WHALES.
Members of the public are asked to stay away from the rescue operation as untrained volunteers may hinder the proceedings.