Aug. 22 (Bloomberg) -- Australian wildlife officials killed a baby humpback whale that was trying to suckle on yachts moored north of Sydney after losing its mother, saying it would otherwise have starved to death.

Vets lifted the calf in a stretcher and sedated it before giving it a lethal injection today, National Parks and Wildlife Service spokesman John Dengate said.

``It's been a harrowing decision to put this calf down, a last resort,'' Dengate said by telephone from Sydney. ``It's a tragic end to a week when dozens of people have put their souls into saving him. Sydney had adopted him.''

The six- to eight-week-old calf, which was 5.5 meters (18 feet) long and weighed two metric tons, was discovered on Aug. 18 near Pittwater, about 35 kilometers (22 miles) north of Sydney trying to suckle on a yacht.

Wildlife rangers lured the calf out to sea earlier this week in the hope it would meet with a pod of passing whales and be adopted by a lactating female. The effort failed and authorities said it was impossible to formula feed the calf for the next 11 months because the richness of the mother's milk and the uniqueness of its teat couldn't be replicated.

DNA Tests

Parks officials are carrying out DNA tests on a female whale carcass with shark-bite wounds found south of Sydney today to determine whether it was the calf's mother, Dengate said. ``It could be a double tragedy,'' he added.

Sydney's Taronga Zoo, Brisbane's SeaWorld, volunteers from the marine mammal rescue group ORRCA and the RSPCA animal welfare organization met yesterday and decided the calf had taken a ``serious turn for the worse'' and that euthanizing it was the most humane thing to do, ORRCA president Ron Ling said by telephone from Sydney today.

The calf had difficulty breathing and had shark-bite wounds, said Ling. The whale was transported to Taronga Zoo for an autopsy.

Whales migrate each year to as far north as the Coral Sea from Antarctica and are followed by predators, including Great White Sharks, Ling said.

Wildlife campaigners said they had applied too late for a court order to try to stop the calf being euthanized.

To contact the reporter on this story: Gemma Daley in Canberra at gdaley@bloomberg.net

Last Updated: August 22, 2008 03:53 EDT