Happy Feet, the emperor penguin who became an international celebrity after losing his way and ending up in New Zealand, is missing presumed eaten after being released into the ocean this month, scientists said.
Concerns were raised over Happy Feet's fate when the tracker device attached to his body stopped sending signals on his trip home to Antarctica.
Kevin Lay, of Sirtrack, the specialist firm that fitted the tracker, said no signal had been received since Friday, when the penguin was about halfway home. He said it was possible Happy Feet had been eaten, but he remained hopeful.
"There are some species that will forage on emperor penguins. It's not likely that it has happened to Happy Feet because of the area he was in."
Lay said the tracker was meant to transmit a signal every time it broke the surface of the water, and had been working perfectly. It was intended to remain attached for months and be shed in the new year moult, but may have fallen off.
Sharks, seals and killer whales are among the creatures known to eat penguins.
The three-and-a-half-year-old Happy Feet was found emaciated and exhausted on a beach near Wellington in mid-June, only the second emperor ever recorded in New Zealand.
He was nursed back to health at Wellington zoo, undergoing surgery to remove several kilos of sand he had swallowed having apparently mistaken it for snow. The zoo's visitor numbers doubled as people tried to catch one of his rare public appearances.
Colin Miskelly, a wildlife expert who advised on the penguin's treatment, said the truth about his fate would probably never be known. "It is unlikely that we will ever know what caused the transmissions to cease, but it is time to harden up to the reality that the penguin has returned to the anonymity from which he emerged," he told AFP.
There are plans for a book and documentary of Happy Feet's story, but the ending may remain a mystery.
The tracker firm posted what may well be the last news of Happy Feet: "Finally, as we expect many people are, the team at Sirtrack are disappointed that we are unable to track Happy Feet's progress any further. We have enjoyed being part of this project and hope that Happy Feet is making his way home."