Penguin puzzle perplexes US zoo

The penguins swim en masse from dawn to dusk

Penguins have become involved in a marathon swimming session at San Francisco Zoo.

Feathers appear to have been ruffled when six new birds were introduced to the colony in November.

Somehow these animals showed they are worthy of being followed

Ian Hiler,
Audobon Aquarium of the Americas

The newcomers from Ohio took to the pool immediately and the other 46 joined in.

But instead of occasional dips, the penguins started swimming frenzied laps of the pool from dawn to dusk.

Nothing has deterred the birds: when zookeepers drained the pool for cleaning, they simply jumped in and waddled around the bottom.

Migration theory

Some experts believe the arrival of new birds from Ohio may have confused the existing colony of Magellan penguins.

One theory is that they are trying to migrate as penguins would in the wild.

The birds come out of the pool to grab food and then go straight back in

Magellans typically travel up to 2,000 miles (3,200 kilometres) in search of food, but captive birds have not shown this type of behaviour before.

Another possible explanation is that the new birds set an example to be followed by the others in their repeated laps of the 130-foot (40-metre) long pool.

Ian Hiler of the Audobon Aquarium of the Americas told the San Francisco Chronicle newspaper: "Usually there are one or two dominant birds.

"Somehow these animals came up and showed they are worthy of being followed."

Behaviour change

Keeper Jane Tollini has looked after penguins for 18 years, but she is baffled by the apparently bird-brained behaviour.

"The minute the six hit the pool, not only did they get in the pool and stay there, they convinced the other birds to do likewise," she said.

They see me, see the fish, run past me, grab the fish and keep going

Jane Tollini,
Penguin keeper

"We've lost complete control."

The marathon swimming sessions are a marked change for the San Francisco penguins.

They used to line up to collect fish from Ms Tollini, who can tell them apart and has a name for each one.

"I am kind of like a drive-through restaurant now," she said.

"They see me, see the fish, run past me, grab the fish and keep going."

The phenomenon could be nearing its end, however.

Ms Tollini thinks there may be a return to the old routine next month, when the onset of the breeding season may lure the birds back to their burrows.