Animals are living longer than ever at the nation’s zoos—but more birthdays mean extra challenges.

In his twilight years, a king cobra named Starfire developed a habit of falling on his back, unable to get back up. Staffers at the Philadelphia Zoo would step up to the exhibit to help Starfire turn over. Then, one day he slipped into his pool and nearly drowned.
He survived for another year in the zoo’s basement, far from the bustle of the exhibits and under the care of keeper Joyce Parker, a 31-year zoo veteran.
“He was so weak, he laid on his side for his last meal. And I had to shed him; I had to pull the shed off of him and kind of drape him over my lap,” recalls Parker, who credits such one-on-one attention with extending the lifespan of geriatric zoo animals. “Whatever I have to do, that extra step that can make them more comfortable. I enjoy doing that.”
When Starfire finally died at the age of 26, he set a world record for longevity. But in his golden years, he was far from alone.
As nutrition, preventative care, diagnostic medicine and habitats improve, a generation of zoo veterinarians and keepers are noticing animals reach much more advanced ages than they did a few decades ago. “A lot of species that used to have a really short lifespan in captivity are now living much longer than they would in the wild,” says Dr. George Kollias, a professor of wildlife medicine at Cornell University’s College of Veterinary Medicine.

Watch as a spectacled langur gets treatment for cardiac disease at the Philadelphia Zoo.

These species include birds, reptiles and large cats. Certain gorillas and orangutans are now living into their 30s and 40s, whereas in the 1970s their life expectancies hovered around 15–20 years. At Syracuse’s Rosamond Gifford Zoo, a kinkajou (a species of rainforest dwellers related to raccoons) blasted through records by living to age 35. Some giraffes and langurs (a type of monkey) are now making it to their late 20s. In Philadelphia, veterinarian Donna Ialeggio estimates that 15 percent of the zoo’s roughly 1,300 animals are senior citizens.
As new species are continually introduced to zoos, part of what is keeping these animals alive longer is simply a matter of experience and care.
“The first time you see a new species in a captive setting, the best thing you can do is take what you know from the wild, and what you know of somebody that’s closely related, and you try to begin the process of matching,” says Ialeggio. “Okay, it’s closely related to a giraffe. It lives in certain environments, it does certain things, therefore you probably ought to feed it this way, you probably ought to give it certain medications and you probably can do x or y. And it’s not always true.”

Watch as keepers and vets care for a white’s treefrog in “a slow decline.”Just as aging humans face a host of new medical challenges, zoo animals are taking up keepers’ and veterinarians’ time with emerging cases of cardiac disease, kidney problems, dementia, menopause, arthritis and dental decay.
Yet, unlike sniffling, complaining humans, “zoo animals—and animals in the wild—are famous for hiding their illnesses,” says Dr. Jim Sikarskie of Michigan State University’s College of Veterinary Medicine and formerly of the Potter Park Zoo in Lansing, Mich.
Despite their attempts to hide their weakness, sick animals may become the target of predators or peers looking to move up in the pecking order. And for animals like Starfire that are undergoing palliative care, keepers must confront the simple issue of how much treatment is too much.
“How do we determine whether we’re doing something for too long,” questions Ialeggio. “What would make that too long is if the animal does not have a good quality of life.”
The decision of when to perform euthanasia is a careful process usually undertaken by an animal welfare committee alongside the input of keepers, veterinarians, curators and (sometimes) zoo directors.
“There’s a real attempt to do it objectively, rather than just say ‘I don’t think this animal is doing well,’” says Kollias. An algorithm is often used that takes into account factors such a quality of life, pain levels, mobility and presence of multiple medical problems.
There are also occasions when an animal’s health can’t be evaluated in isolation from its environment.
A few years back, Ialeggio treated a female African wild dog, Malindi, who had recently been diagnosed with advanced stage cancer. Because her disease was incurable and all the zoo could do was relieve her pain, euthanasia “might have been the right decision,” Ialeggio says.
African wild dogs, however, are a very social species in which, like humans, males and females form close pair bonds. Euthanizing Malindi without other available dogs on hand would have put her male mate, Kenya, “into a very severe behavioral situation that would have been very, very difficult physically and emotionally for that dog,” Ialeggio recalls. In the end, Malindi received palliative treatment until more African wild dogs could be moved to the zoo to introduce to Kenya after Malindi’s death.
In Philadelphia’s primate wing, keeper Mandy Fischer treats another particularly social species, the spectacled langurs. The family’s matriarch, nearly 26-year-old Spot, has recently been diagnosed with an enlarged heart.
Although Spot is the continent’s second oldest langur in captivity, Fischer says she’s holding up, taking medication with her grapes every morning.
“The toughest thing about being a zoo keeper is knowing that we’ll probably outlive most of our animals,” Fischer says. When Spot does die, “it’s going to be really hard, but she has amazing kids that I get to work with in here. She kind of has a legacy going on.”
Survival Keys: Veterinary developments mimic the way modern medicine has doubled human life expectancies over the last few centuries. In our interactive graphic, learn about a few of these developments.