Fears are growing for the wellbeing of Happy Feet, an emperor penguin who washed up on a New Zealand beach, after scientists lost contact with the bird. A transmitter attached to the penguin earlier this month on his release back into the wild stopped relaying information on his location on Friday. Researchers said Happy Feet may have been eaten, or the tracking device may have failed or fallen off.The bird was found emaciated on a beach in June, hundreds of miles off course. There are many theories abounding over the sudden loss of contact with Happy Feet. Kevin Lay from Sirtrack widlife tracking team told local media that the most likely explanation was that the transmitter had fallen off the penguin. \"To be uninvasive, we only glued it on so that it would fall off. We hoped it would stay on for five or six months, but it appears in this case it\'s only stayed on for two weeks,\" he told TVNZ. Mr Lay said it was possible the penguin had been eaten, but that this was doubtful. \"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,\" he said. Wildlife expert Colin Miskelly, who advised on Happy Feet\'s treatment, told AFP news agency that efforts to find the penguin would continue. \"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 the news agency. Happy Feet was released from the research vessel Tangaroa on 4 September into the Southern Ocean about 50 miles (80km) north of the remote Campbell Island. He was returned to the wild after recovering from surgery to remove 3kg (6.6lb) of sand from his stomach.His unexpected appearance on Peka Peka Beach - north of Wellington and 3,000km (1,860 miles) from his Antarctic colony - stunned wildlife experts who said he was only the second emperor ever recorded in New Zealand.He is thought to have eaten the sand, having mistaken it for the snow penguins swallow to stay hydrated.