Amusing Bozo: Zoo keepers look for enrichment to fight animal boredom

ST. LOUIS -- Bozo the baboon grabs a small plastic cage, filled with cabbage and green beans, and heaves it across his pen. His fluffy, gray hair bounces as he trots after it.

Four female baboons have figured out how to unlatch their food cages. They sit on their crimson bottoms and munch the vegetables. Bozo keeps flinging his cage until it bursts open.

"He's not the brightest bulb," said St. Louis Zoo primate keeper Ingrid Porton.

The scene amuses a family, but it's not for their benefit. The cages are supposed to amuse the baboons. Don't call the cages toys, however. They are "enrichment," according to Porton.

Zoos used to be content with being humane. Now, they have to entertain. Since 2002, the American Zoo and Aquarium Association has required its 211 accredited members to have an enrichment program. The practice reflects a growing body of research that says bored animals are unhealthy animals.

"It's kind of hard to define animal boredom," said Denise Leonard, a doctoral student in animal behavior at St. Louis University. "We can't ask the animal."

David Shepherdson, a researcher at the Oregon Zoo, adds that there's a danger in presuming that animals will enjoy what humans enjoy -- or that animals can "enjoy" anything at all.

What zookeepers do know is that stimulated animals seem to be healthier. Without stimulation, they say, animals show "stereotypic behavior." Birds pluck themselves. Big cats chew their tails. Primates pick a wound for no reason.

Shepherdson said he has found high stress hormone levels in polar bears that pace back and forth. Now, studies are showing that enrichment -- whether a food puzzle or a change in the animals' pens -- can help reduce that stress.

Nadja Wielebnowski, an ecologist at the Brookfield Zoo in Chicago, has studied 74 captive clouded leopards. The clouded leopard is a secretive cat that likes to climb. Wielebnowski found higher levels of stress hormones when pens were smaller and less elaborate.

Wielebnowski then added hiding and climbing spaces to leopard pens in six of the zoos she studied. Stress levels dropped, she said.

The science backing up enrichment may just be emerging, but zoos have been doing it for years. Porton said the St. Louis Zoo began its enrichment program in 1996.

"We've seen a complete evolution," she said. "Older keepers just wanted to do the routine. Now the keepers think it's wrong if you don't do" enrichment.

At zoos, the question now isn't so much whether enrichment is good. It's what type of enrichment works best.

With small budgets, zoos are finding ways to make enrichment creative and economical.

At the National Zoo in Washington, an octopus gets to unscrew a jar filled with shrimp. The Oregon Zoo gives its polar bears whole salmon frozen in a five-gallon bucket of ice.

At the St. Louis Zoo, a purple hyacinth macaw chews on the end of a long cardboard tube that sometimes has bananas in it. A 42-year-old caracara, a scavenging raptor, peers into a papier mache hive and gobbles up the dead mouse hidden within.

There's enrichment even in the insect house, though invertebrate keeper Bob Merz acknowledges that sometimes his insects are the enrichment for other zoo animals.

Merz said insects don't have a mental life -- that the banana slug doesn't enjoy its special cucumber treat. But there are real effects on an insect's health if its environment isn't enriching, he said. A meal will rot within a scorpion, for example, if it's not stimulated to move around within its exhibit.

With other exhibits, however, the enrichment is more for the visitors than the insects. Behind glass, a buzzing community of paper wasps has made a rainbow-colored nest from scraps of red, orange and green paper.

"That's for us, mainly," Merz said.