So, the zoo nutritionists got together for a 2-day meeting at NCSU to discuss the issue:
Obesity among zoo animals is such a complex problem that zoo nutritionists, scientists and others, from as far away as England, gathered at N.C. State University on Friday for a two-day symposium on such weighty matters as how to tell when an oyster's weight is about right.
"It's actually a huge problem, and a multifaceted one," said Michael Stoskopf, a professor at the college. "You have to look at not only diets themselves and the amount of calories delivered, but also things like exercise."
The basic cause of chubbiness is no different for moray eels and wildebeests than for humans: "If the energy going in exceeds the energy going out, you're going to get fat," said Karen Lisi, a nutritionist at the Smithsonian National Zoological Park. "We don't like to hear that, but that's pretty much how it is for us, too."
With so much variation among creatures, though, nutritionists have to treat the diet of each species almost like an individual scientific study, determining what it eats in the wild and how best to approximate it in captivity, said Richard Bergl, curator of conservation and research at the N.C. Zoological Park in Asheboro.
"It's not just a matter of throwing a bucket of apples in with the monkeys and a bale of hay to the elephant," Bergl said.
When your zoo has hundreds of creatures as different as tree frogs, fish, birds and elephants, the task can be overwhelming.
Even among birds, the variation in diet is huge, what with hummingbirds that sip nectar, fruit-eating parrots and vultures that chow down on rotted meat. The diet for individual animals may have to be adjusted to compensate for changes such as pregnancy, lactation or simply aging, Lisi said.
Her zoo, with about 400 species and 2,000 individual animals, has its own nutrition lab.
Even simply determining whether an animal is overweight is so complex that part of the symposium was dedicated solely to that topic. Sometimes it's obvious when an animal is morbidly obese, Lisi said. Other times, though, a quirk of a given species, such as thick fur, makes it more difficult, and zoo staff might not be able to tell without tranquilizing it and checking by hand.
Read the entire article (which, btw, is the front-page, big-headline piece in today's News & Observer - kudos to the newspaper for putting science up front).
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But are American zoo animals fatter than European animals or even Japanese animals?
We just got an update today on orangutan weights at the zoo where I volunteer: Good news. Everyone is going in the right direction. Maintaining the weight of apes is a real challenge, especially with an older population that doesn't exert as much energy at "play" as youngsters do. And it's hard to figure out new (and safe) forms of enrichment that don't include food.
Food prep for the littlest mammals is so precise. We measure out and chop 6 grams of apple, 8 grams of banana. Count out 4 (live) worms. And some of the diets are so complex. Twice a day. Then, when you remove the dish, you measure and record what's left to keep track of changes in their appetites.