Spend enough time behind bars - at the Baltimore Zoo - and your natural instincts are likely to be dulled.
There are few opportunities for truly wild play. Food doesn't have to be caught or killed.
So zoo officials, with the help of some kids ages 11 to 14, created something that sounds like it came out of a yuppie child-raising guide: "enrichment toys."
The children made them out of colored wood, leather strings and paper mache, and filled and adorned them with dried fruit and other foods. The animals did the rest.
Two fearsome, bald-headed vultures attacked sailors' knots thrown into their yard, exercising their primordial instinct to rip things apart.
Promo, a white sulfur-crested cockatoo from Indonesia, used his buzzsaw beak to devour the tucked-away dried apricots in his toy - putting to rest questions the kids and head birdkeeper James Ballance had about how Promo would respond.
"It's different than anything he's seen before," Ballance said last week, as the exotic bird devoured the treat. "We try to keep it as spontaneous as we reasonably can."
Making the bird toys look tropical, with wood dyed with food coloring, is worth doing, Ballance explains, because "birds can see color, so it's a great thing."
Engaging natural instincts
Making the birds work and play to open up something eye-catching is constructive, the theory goes, because it engages natural instincts they may have largely lost in captivity.
Tyler McIntosh, 11, put it bluntly: "They must be bored out of their minds. They need to be exercised mentally and physically."
He was referring not only to the birds but to Pete, the American black bear, and the monkeys and chimps. For them, the kids' teachers designated paper mache, a better medium for larger animals.
Bird seed and Cheerios generally lined the toys for the monkeys and chimps. The feeders took special care to give Simba, a diabetic monkey, her special diet. Peanut butter, raisins and cinnamon were in store for the bear.
"We made them as strong as we could," said Seth Baglin, 14, "but he [Pete] batted it for a few minutes and tore it apart."
The monkeys and chimps are pretty strong, too.
"They enjoy themselves," said another child, "but your carefully made creation is gone in 30 seconds."
That's enrichment, kids.
The children were selected from essays they wrote; all were identified as "gifted and talented," Sabrina Raymond, the Zoo's community programs coordinator, said. Drawn from all over the area, they spent two weeks at the zoo, learning to make the toys and watching the keepers give them to various birds and other animals.
Making enrichment toys has proved so popular with kids and keepers alike that the program will continue through the summer with other groups, zoo officials said.
As their work progressed, students came to see that even if it was intended for the animals, enrichment really worked both ways.
"I like watching them enjoy what we make," said John Barcase, 13.
Hal Chang, 12, agreed as he contemplated what it meant to make something that animated a red-bellied woodpecker.
"You have more interest, thought and liking for the bird than you did before," he said.