Stuff Digital Edition

Scientists still puzzled over cause of mass strandings

– The Times – The Times

The discovery of more than 200 black pilot whales strewn along a beach on Tasmania’s west coast has left marine scientists scratching their heads.

The mass stranding on Wednesday at Macquarie Harbour near the port town of Strahan took place two years to the day after almost 400 pilot whales died on the same stretch of beach, in the worst recorded stranding in Australia’s history.

Dr Vanessa Pirotta, a Sydney marine scientist, said the strandings were a mystery. She and many of her colleagues have theories, including that a sick whale led the pod into shallow waters, or that something might have panicked them, or maybe a miscalculation led the whales to be beached.

The latter possibility is receiving attention because of the similarities to the 2020 event, when 470 long-finned pilot whales stranded in one day.

Pirotta said the repeated strandings suggested that ‘‘there might be something environmental here’’.

Researchers in New Zealand have found that live mass whale and dolphin strandings are clustered at ‘‘stranding hotspots’’.

Some experts have suggested that these hotspots are the equivalent of the legendary elephant graveyards. However, this does not explain why young or healthy whales become stranded.

The New Zealand study found it unlikely that harassment by predators, such as orca, caused the mass strandings.

New Zealand Geographic magazine made the observation that gently sloping beaches are natural ‘‘whale traps’’.

‘‘Species unfamiliar with this kind of topography and its associated tides and currents find themselves getting shallower and shallower, until it’s too late to retreat,’’ it said. The site of the strandings this week and in 2020 fits this description.

Dr Kris Carlyon, the wildlife biologist who managed the Tasmanian rescue operation, said he supported the whale trap theory. The whales’ echolocation system might have been disrupted by the area’s shallow waters and sandbanks, he said.

‘‘We have seen multiple stranding events at this location, both with pilot whales and other species like dolphins.’’

Efforts in Tasmania have turned to the task of disposing of the animals that could not be saved. Of the 40 found alive on Thursday, 30 were returned safely to deep water. The hundreds of whale carcasses will be towed out to sea.

WORLD

en-nz

2022-09-25T07:00:00.0000000Z

2022-09-25T07:00:00.0000000Z

https://fairfaxmedia.pressreader.com/article/287191586787088

Stuff Limited