BROWNSVILLE, Texas—Cindy Stones is the foster parent to hundreds of animals at the Gladys Porter Zoo.

Whether she has bottle-fed them, cared for them when they were sick or just watched them grow up, Stones has had a hand in raising almost every animal born at the zoo.

“I get really attached to the animals,” the 28-year zoo veteran said.

And the animals have gotten attached to her—like the two female gorillas that recently gave birth.

While the animals will try to scare off anyone else who enters their space, the gorillas happily show their offspring to Stones as she makes her morning rounds. They themselves were bottle-raised by her.

Stones gives each of the gorillas vitamins.

The female gorillas receive birth control pills, and the nursing moms take prenatal vitamins. She talks to each of the gorillas as she distributes the medicine, which has been well hidden in everything from Kool-Aid to peanut butter sandwiches.

“They’re like family,” she said. “They get kind of attached to us.”

Stones is the supervisor of Small World, the section of the zoo focused on young animals. It includes a nursery where young animals go if there mothers are unable or unwilling to care for them. Such was the fate of two dama gazelles. One was born on Sept.15, the other on Sept. 9.

Like a human nursery, Stones and the other keepers who work in the area provide around-the-clock care for the baby animals. They take a bottle of milk every two hours and have their weight and temperature checked every day. But her ultimate goal for these animals is to reunite them with their families.

“The animals are number one,” she said. “It’s very gratifying to see babies grow up, to see the hand-raised babies have their own babies and take care of their own. I love to see them thrive.”

Part of helping animals thrive involves enriching their lives with different foods, toys and activities. All animals at the zoo receive some kind of enrichment every day, and the enrichment differs from day to day. The challenge is finding toys, food and activities that are safe but still enjoyable for the animals, the exhibit, the zookeepers and the general public.

Like people, animals can be fickle, and entertaining them isn’t always easy.

Stones explained that the gorillas used to love cardboard. They would get a box and play with it for hours, pushing it across the floor and hopping in and out of it. Then the zoo acquired a new gorilla from another zoo. That gorilla taught all of the other gorillas to eat the cardboard instead of play with it. Now the gorillas only get cardboard once a year around Christmastime.

The same held true for the big cat—one old male leopard forced the keepers to completely alter their enrichment program. The keepers had decided to mirror what other zoos across the country were doing by giving meat to the big cats in burlap bags. All of the other big cats had fun pulling the meat out of the bag, but the old leopard decided to eat the burlap bag with the meat in it. That was the end of providing meat in a burlap bag.

“Some things work for 90 percent of the animals,” Stones said. “You have to continue to monitor in case there’s change.”

Stones loves the challenge of enriching and caring for the animals, though.

“Even on bad days when you’re dealing with diarrhea, you need to step back and say this is why I’m here,” she said. “You have to really want to work with the animals and really want to be here.”