HOUSTON -- Novia was the Houston Zoo’s no-show ocelot. Eager crowds gathered for a glimpse of the leopard-spotted South American wildcat, but she only warily eyed them from inside her den. When surprised by humans while out for a rare stroll, she darted to safety. It was a strange cat-and-mouse game that left zoo visitors disappointed.
To zookeepers, it was clear that Novia, just a year old, was one stressed kitty. Such anxiety, they knew, was bad for visitors, bad for zoos and bad for animals.
Unresolved, stress can make blue-hued banded iguanas turn black, piranhas snack on their tankmates, parrots yank out their feathers and snakes coil and rattle. No animal confined in a zoo is immune to stress, and American zoos collectively spend millions to see that it doesn’t happen.
"I would argue that being in a zoo doesn’t in and of itself cause stress," said Hollie Colahan, the Houston Zoo’s curator for primates and carnivores. "So, I think you have to look at the individual animals and their backgrounds. . Life in the wild is stressful."
Colahan leads the zoo’s enrichment committee, a body made up of animal keepers and others who try to find ways to lessen the possibility of stress. Employing the skills of Sherlock Holmes and Sigmund Freud, committee members meet monthly to take up cases like Novia’s.
The zoo’s 100 keepers, spokesman Brian Hill said, are the institution’s first line of defense in battling animal stress. At a facility with 6,000 animals representing 800 species, keepers— also charged with feeding animals and cleaning pens—must be ever alert to stress indicators that all but the keenest eye might miss.
Novia’s keepers quickly determined that the cat never had been exhibited at its previous zoo.
Working with the frightened animal to gain her trust, they gradually introduced her to the public. At first, she was brought into the exhibit area late in the afternoon, then for brief periods in the morning. Bravery was rewarded with mouse treats.
The strategy paid off within weeks as the once-skittish ocelot braved the scrutiny of zoo patrons.
Joining keepers in battling stress, Hill said, are zoo veterinarians and even architects. Building low-stress enclosures that mimic natural range was a key goal at the zoo’s newly opened $42 million African Forest.
"It’s all about prevention," said Hill, who noted that other exhibits were designed with the animals’ natural habitats in mind.
"The eland share the exhibit with warthogs, kudu, zebras and a dorcas gazelle," Hill said. "These species share the same range in the wild, so it is an appropriate and comfortable setting for them here. In fact, one of our zebras, Joplin, and our dorcas gazelle have formed such a bond that they are almost inseparable."
Novia’s stressed-out state—like those of some afflicted animals—was fairly apparent.
"With a rattlesnake, it’s coiled and its tail rattles and if its tongue is out going up and down, it’s telling you in every way possible, ‘Please get out of here,"’ said Stan Mays, the zoo’s reptile curator. "A banded iguana, normally blue or green, will turn black if it gets upset enough. It will breathe heavily, and its heart rate will increase."
Those are clear signs of trouble, but, for many animals, the indicators are harder to read. Keepers must not only know a species’ expected behavior, but the quirks and oddities of individuals. Boas, after all, will be boas.
Does an antelope’s twitching ear mean it’s stressed, mad enough to fight or that it’s just bothered by a fly? Is an adolescent chimpanzee’s unruly behavior a sign of dangerous aggression or just immature posturing?
"Chimps are as different as people," Colahan said. "It’s very normal chimp behavior for them to be running around, screaming, punching and throwing. Our goal is to ensure that normal behavior doesn’t cross the line to the point that it becomes harmful."
While a human patient exhibiting symptoms of stress might be calmed by a doctor’s prescription, zoo officials are reluctant to treat animals with pills.
"If my doctor puts me on a drug," Colahan said, "I can tell him if I’m feeling funny or my stomach hurts. Animals can’t give that kind of feedback. . We don’t want to jump to fix problems with a pill right away. We’d rather get to the root of the cause, to alter the animal’s environment, if necessary."
In worst-case scenarios, animals retire to off-exhibit areas to live their lives in secluded comfort, although some were expected to return to public view.
"There are animals that never will go on exhibit," said Judith Bryja, reptile supervisor. "Some do really great. Some just stress out."
She cited the case of two banded iguanas—brothers—who were raised in an identical manner.
One, a stressed wreck after a few hours’ exhibit, turned black and permanently was retired. The other became an endearing show hound.
Animals that exhibit signs of stress first are checked by veterinarians to rule out sickness, zoo officials said.
"When we wonder if they’re just crazy, we have them checked for underlying medical conditions," said bird curator Hannah Bailey. Thus, doctors determined that the odd foot pecking of the zoo’s green jays had a medical cause.
Much of the wisdom of enriching zoo environments came as an outgrowth of research by members of the National Association of Zoos and Aquariums. "Enrichment can mean a lot of things," AZA spokesman Steve Feldman said. "It can be putting scent in the big cat enclosure or providing places for fishes to hide."
At Houston Zoo’s new African Forest, keepers start the morning scattering food throughout the chimp habitat to stimulate the animals’ instinct for foraging.
For birds, reducing stress can be as basic as providing the right-size cage, one that allows for flight, and strategic plantings and perches.
At the aquarium, enrichment takes the form of tanks that, equipped with fake tree trunks or coral reefs, mimic the natural environment.
The problematic behavior of piranhas is an ongoing area of inquiry for Colahan’s enrichment committee. The panel has compiled a list of positive piranha traits, which they try to encourage, and nastier behaviors that should be discouraged.
Among the latter is a tendency to eat their tankmates.
"We try by proper food selection, proper nutrients, proper amounts to cut down on their aggressiveness," aquarium curator George Brandy said. "They are predators. They eat other fish. They are known to cannibalize."
Keepers on the enrichment committee also are exploring mysterious piranha behavior—the ability to vibrate and make clicking noises and their apparent attraction to Aggie maroon clothing worn by their keepers.
"That color of clothing thing," said Brandy, "is just a hypothesis."