Fears were growing Tuesday for the survival chances of a lost baby humpback whale who tried to suckle from an Australian yacht in the belief it was its mother.

Wildlife experts used the yacht to lure the calf out of Pittwater bay near Sydney's Palm Beach on Monday, hoping it would link up with other whales passing by on their annual breeding migration.

An ABC TV framegrab shows a baby humpback whale trying to suckle from an yacht near Sydney. Fears are growing for the survival chances of a lost baby humpback whale who tried to suckle from an Australian yacht in the belief it was its mother. [Agencies]

But on Tuesday the calf was back among the anchored yachts in the vast bay, having failed to find either its own mother or a surrogate, Department of National Parks and Wildlife spokesman Chris McIntosh told AFP.

"We successfully lured the calf about a kilometre out to sea -- probably the first time that's been done using a yacht as a surrogate mother," he said.

"Later we saw whales a bit further offshore and there was a slender chance it may have linked up with them, but this morning we have got reports that it has returned to the western shores of Pittwater."

McIntosh said the calf now most likely faced the prospect of dying of hunger, being attacked by sharks or stranding itself.

"While it's moving quite freely at the moment, its condition would be expected to deteriorate over the next three days," he said. "There is very little hope, virtually none."

McIntosh said that if the calf became stranded or beached itself, mercy killing will be considered.

The calf showed no signs of injury, apart from some lacerations apparently caused by rubbing up against the boats, and it was believed likely to have simply been rejected by its mother.

"We've consistently said it was a slim chance that it might link up with its mother or other whales but the reality is that in the wild, for various reasons, mothers sometimes reject their young," McIntosh said.

The calf was estimated to be two months old, about five metres (yards) long and to weigh five tonnes, but it would still rely primarily on its mother's milk and its chances of survival without it were negligible.

"Looking at its behaviour, the way it was nuzzling up to yachts, would indicate it was primarily still suckling," McIntosh said.

"It really was trying to suckle, just below the waterline and against the keel, with its head engaged against the boat."

It would be difficult to lure the calf out to sea again now that it had lost its strong attachment to a particular boat, and attempts to herd it would cause unacceptable stress, he said.

The humpbacks are on the return leg of a remarkable annual round trip from the Antarctic to tropical waters to breed, and they can be seen ploughing homewards not far off Sydney's beaches on most days.

(China Daily via Agencies?August 20, 2008)