Tokyo residents are on the lookout for a one-year-old Humboldt penguin that escaped from his enclosure at the Tokyo Sea Life Park zoo over the weekend.

According to Takashi Sugino at the harbor-front aquarium, the wayward bird scaled a sheer rock face to escape and was last seen swimming in a nearby river.

We first noticed the penguin might have fled when the director of a neighboring zoo emailed us Sunday with a photo, Sugino told AFP news agency.

A second photo provided by a visitor enabled Sugino and his crew to identify the bird as a Humboldt penguin that hatched last January. The penguin lives with 134 others in the enclosure.

Of course it can't fly, but sometimes wildlife have an 'explosive' power when frightened by something, Sugino added. Maybe it ran up the rock after being surprised.

On Sunday, onlookers snapped photos of the young penguin bathing in the mouth of the Old Edogawa River, which runs into Tokyo Bay.

It's a bit of a struggle to catch it when it is swimming because it swims at a tremendous speed, Sugino said. We are hoping to catch it when it climbs up on land to sleep.

The incident mimics the events of the 2005 animated film Madagascar where penguins, among other animals, mount an escape from the zoo.

The Humboldt penguin is already a long way from home. Named after the scientific explorer Alexander von Humboldt, the medium-sized penguin is native to the Pacific coast of South America and offshore islands of Chile and Peru.

Humboldt penguins have a black head with a white border that runs from behind the eye, around the black ear-coverts and chin, and joins at the throat. With an estimated population of between 3,300 and 12,000, they are currently listed as threatened due in part to over-fishing, climate change, and ocean acidification.

The Tokyo Sea Life Park put up posters inside the park and posted a notice on its Web site seeking tips from the public.

In the event that you see a penguin on the loose, please let us know and don't run after it or try to catch it, the park said in the announcement.

In the meantime, onlookers said the escaped penguin appeared to be having a grand time swimming his way around Tokyo.