Sometimes regular meals and the companionship of scores of other penguins just aren't enough. Penguin Number 337 seems to have decided something was missing from life at a Tokyo aquarium and took off.

The one-year-old Humboldt penguin scaled a rock wall and squeezed through a fence during a daring bid for freedom some time in the past week, sparking a penguin hunt that included a city-wide call for information on the tubby fugitive.

---

Tokyo Sea Life Park, on the shores of Tokyo Bay, was alerted to the escape of the bird, known only by its number, after receiving a photograph on Sunday that supposedly showed it swimming in the bay.

'Yearning for adventure'
Kazuhiro Sakamoto, the park's deputy director, thinks it may have been a case of happy feet.

"The penguin hatched last year on January 27, so it is still a very young penguin," Sakamoto said.

"We think that because of its young age, it might have escaped due to its curiosity and yearning for adventure."

The bird, still too young for keepers to determine whether it was male or female, shared life at a rocky outdoor enclosure with a view of the sea with 135 other Humboldts and a number of penguins of other breeds. Humboldts grow to 22-28 inches long and can weigh up to 13 pounds.

Animal Tracks: Penguin on the loose

But getting out would have been far from simple.

"There's a man-made rock wall that varies between 4 to 13 feet high. After somehow climbing over it and getting out, it appears the penguin managed to squeeze through a gap in the outer fence," Sakamoto said.

Worries over dirty sea water
Worried that the penguin might have strayed out to sea, keepers issued a Tokyo-wide call for tips on the feathered fugitive and are making regular patrols along the shoreline in front of the aquarium, staring out to sea with binoculars.

Visitors said they were worried about the bird. The area around the aquarium, which sits where the Edo River empties into the bay, consists of high-rise apartment buildings and concrete, with a highway looping overhead.

"The sea water around here is very dirty, so unless the penguin is returned to safety quickly it may die," said Hiroki Kasai, a university student.

Others felt it may have gone in search of more salubrious living quarters, noting that the penguin enclosure was much more cramped than its natural habitat.

Sakamoto said the waters of the bay were full of fish so the penguin was unlikely to starve -- but that it was also unlikely to head for Peru or Chile, the ancestral home of Humboldts.

"It's a type of penguin that tends to stay close to shore, but I also think it would not be able to cross all of that wide ocean."

More from msnbc.com and NBC News:

• Palestinian women allege abuses by Israeli security service
• Stranded kite surfer fends of shark for two days in Red Sea
• High stakes for China iPad dispute
• Obama: US not staying in Afghanistan longer than necessary
• French report: Ban beauty pageants, padded bras for little girls

Follow us on Twitter: @msnbc_world

Copyright 2013 Thomson Reuters. Click for restrictions.