BEACHED: Sperm whales at Perkins Island in the North-West in January 2009.
THE craggy coast and wild seas that give Tasmania's West and North-West coasts their beauty also make the region a deadly trap for whales and dolphins.
The latest beachings just over a week ago resulted in 82 dolphins and pilot whales dying in two separate mass strandings on King and New Year islands.
Locals and Parks and Wildlife staff were able to rescue 15 and return them to the sea.
Whale and dolphin strandings occur in Tasmania more often than any other Australian state, and a disproportionate number of these occur in the Circular Head, Macquarie Island to Ocean Beach areas, as well as King Island.
Twenty-two sperm whales were stranded on Ocean Beach near Strahan in November last year, almost 200 pilot whales and dolphins beached at Naracoopa on King Island in March 2009, 64 pilot whales were stranded at Stanley in November 2008 and 48 sperm whales near Smithton in January that year.
Rosemary Gales, biodiversity monitoring manager for the Department of Primary Industries, Parks, Water and Environment, said both the North-West and West coasts had complex topography which, combined with the state's proximity to the whale haven of the Southern Ocean, may account for their reputation as a whale trap. Gently sloping beaches can be difficult for whales and dolphins to detect because they do not reflect sonar and the creatures stray too close to shore. Bays with narrow entrances flanked by rocky headlands can give whales and dolphins the illusion they are trapped.
Dr Gales said the recent King Island strandings may have been a result of the animals becoming confused by the coastline.
"Like most mass strandings, especially with pilot whales and dolphins, there were probably a number of factors that contributed to the stranding. At least one of the sites had very complicated topography and possibly the animals got trapped," she said.
"It was particularly interesting because there were both pilot whales and bottlenose dolphins.
"It's always those two species [that beach together] and we know they interact together at sea and they feed on the same sort of prey.
"Single strandings are very different to mass strandings, which typically involve healthy animals.
"Generally [mass strandings involved] toothed whales or dolphins, which have very strong social structures. A couple may get stuck, call out to others, which head towards it and also get stuck."
While human activities such as the use of ship sonar have been proven to cause strandings in other parts of the world, Dr Gales said there was no evidence that was a factor in strandings in Australia.
"Overseas in the US they have had this, but it's dangerous to extrapolate to other areas and other strandings and infer that all beach whale strandings must be because of sonar," she said.
Departmental staff take samples from dead whales in an attempt to develop a better understanding of why it is occurring.
"We look at DNA and we collaborate with New Zealand and we've worked out that the pilot whales that strand in Tasmania are generally very different to the pilot whales that strand in New Zealand," Dr Gales said. "Other things we look at is the age of the whale and basic biology, including their size and condition. We also check things like pollutant loads."
The stranding season generally starts around November as the whales make their way south.
People finding a whale or dolphin stranding can call the 24-hour DPIPWE hotline on 0427 WHALES.
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