Conservationists are demanding an immediate and thorough inquiry into what they say is the suspicious stranding of 200 whales and dolphins.

Fears that the mass stranding on an Australian beach on Sunday was caused by human disturbance were raised because two species of cetacean came ashore simultaneously.

Most of the animals were pilot whales, but a number of bottlenose dolphins were also among the pod.

Residents joined wildlife workers to spend hours keeping the surviving animals wet and cool before they could be lifted, pushed and hauled back into the water.

The rescue operation succeeded in saving 54 pilot whales and five dolphins on Naracoopa Beach on King Island, Tasmania. Most of the beached animals were dead by the time anyone could reach them.

Wildlife workers and volunteers were delighted to have saved more than a quarter of the whales and dolphins, but they were maintaining a watch on beaches in the area for fear that some of the creatures might come ashore again during the next high tides. Officials of the Tasmanian Parks and Wildlife Service were trying to discover last night why 192 whales and seven dolphins had beached themselves but said that the stranding, like many others before, was likely to remain a mystery.

Mark Simmonds, of the Whale and Dolphin Conservation Society and an expert on cetacean strandings, said that two species coming ashore together was enough to arouse suspicions of a human factor, including the use of sonar by the military.

“To get more than one species is unusual,” he said. “When you do, you get more suspicious because it means that they might have been driven. It does make us worried. We are certainly going to call for a very thorough investigation.”

Military sonar has been strongly linked to several strandings, particularly of deep-diving species such as pilot whales. Other human noises that could have frightened or disorientated the animals include industrial activities.

Another prime suspect among the possible causes is climate change, which scientists fear may be causing whales and dolphins to get close to unfamiliar coastlines.

Several species have migrations that take them close to the Tasmanian shore - 80 per cent of Australian strandings take place in Tasmania - and changes in water temperature caused by climate change could be driving them off their usual routes.

However, Dr Simmonds accepted that an explanation for the stranding could equally well be natural, such as the marine animals making a simple navigational error.

Factors leading to natural strandings are little understood but researchers believe that they are likely to be linked to group behaviour.

“Pilot whales are one of those species that do tend to feature in mass strandings, which is probably because they are a very social species,” Dr Simmonds said. “Out at sea there's nowhere to hide but behind each other, so when one gets into trouble the others follow.”

It is the fourth time in the past few months that a large stranding has taken place on Tasmania's coast. Chris Arthur, of the Parks and Wildlife Service, said: “This last summer has been a particularly demanding one.”

Ninety-seven animals of two species - long-finned whales and bottlenose dolphins - were stranded in November 2004 on King Island.

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