WELLINGTON, New Zealand (AP) — The penguin known as “Happy Feet” has vanished in the ocean on his way home from New Zealand, eluding his trackers just days after his release and leaving behind a mystery that may never be solved.

After seizing global celebrity by going off-course and landing on a New Zealand beach far from its Antarctic abode, the emperor penguin has simply disappeared from the grid.

Happy Feet’s satellite transmitter went silent Friday, five days after experts released the bird from a research ship into the Southern Ocean about a quarter of the way down to Antarctica.

Initial dispatches from the device showed that Happy Feet swam in a meandering route, ending up about 75 miles (120 kilometers) southeast of where he began by the time the last transmission came across Friday morning. Experts say his looping pattern was typical for a penguin chasing fish.

At this point, the transmitter may have simply fallen off, experts tell the Associated Press. It was attached to the bird’s feathers with super glue and was supposed to fall off anyway early next year when he molted.

“Who knows? He’s probably swimming along quite happily without a transmitter on his back,” said Peter Simpson, a program manager at New Zealand’s department of conservation.