Australian wildlife experts were racing against time today to save a lost baby humpback whale that has been nuzzling up to yachts believing they could be its mother.

The calf, about two months old, was abandoned or became separated from its mother during the annual breeding migration. Humpbacks undergo a 20,000km round-trip from the Antarctic to the warm waters of Queensland.

It was first spotted in Sydney's Pittwater Bay on Sunday trying to suckle from a whale-sized yacht, in a vain attempt to get a response from its "surrogate mother".

Yesterday, rangers used the yacht to lure the calf out to open sea in the hope it would find its mother or join other migrating humpbacks. But today, it was back in the same area, on the western shores of Pittwater, circling other yachts.

A spokesman for the department of national parks and wildlife, Chris McIntosh, said the 5m-long calf risked dying of hunger, being attacked by sharks, or beaching itself.

"The difficulty with this calf, in our view, is that it probably hasn't weaned itself from its mother and that is why it is taking to yachts. The prognosis isn't good," said McIntosh.

The humpback's dilemma has generated a huge outpouring of sympathy in Australia, with television and radio stations keeping a watching brief on the drama.

The Sydney Morning Herald reported today that a grey whale calf called JJ was rescued off the coast of California in 1997 and bottle-fed a special formula before being successfully released back to the ocean.

Wildlife experts in Australia have contacted the US water park Sea World to see if there is any hope of doing the same thing with the calf, but artificial feeding in captivity is extremely rare. Rescuers believe it would not succeed because the lost calf is relatively large, weighing about five tonnes, and is already distressed. Australia also does not have the facilities or experience to attempt artificial feeding.

Whale calves normally stay with their mothers for up to 11 months, although at two months they start to eat some solids. Rangers say the lost baby humpback will survive only a matter of days without the nourishment of its mother's milk. Euthanasia might become an option if the young mammal beaches itself or becomes too distressed.

"It's heart-wrenching but the reality is that in the wild, for various reasons, mothers sometimes reject their young," said McIntosh.