March 20, 2008
Caring for the Lincoln Park Zoo’s Oldest Animals
CHICAGO -- Veterinarian Kathryn Gamble sat next to a table in Chicago's Lincoln Park Zoo Hospital the other day polishing the big, sharp teeth of an anesthetized black leopard with bubble-gum flavored toothpaste.
A dozen zoo personnel watched anxiously during this annual physical for Marta the leopard, a frail dowager at 18 years old. The jet-black cat is a favorite of keepers for her gentle, people-oriented nature, but she has not been well for years thanks to the maladies of old age.
Arthritis has slowed her. Her teeth are breaking down. A year ago Gamble found a mysterious, possibly fatal mass of tissue growing in her snout. On top of this, she has developed severe allergies to her food, grass, soil, her toys, even odors like cleaning fluids.
Still on display in a carefully managed space, the big cat is a good example of zoos' success in keeping their animals alive longer than ever with improved husbandry and medical attention. But as a consequence, zoos now struggle to care for animals with increasingly difficult geriatric problems.
Marta most likely would be dead by now if she lived in the wild, as she is too decrepit to survive. Confiscated as an illegal pet before she was a year old from private owners who had declawed and spayed her, she arrived as a cub at Lincoln Park in 1990.
As a non-breeding member of a species not in danger of extinction, Marta might seem like extra baggage in a zoo setting. But she has collected her share of admirers over the years.
Though baby zoo animals are the most popular with the public, and vigorous young adult animals show species at their peak of beauty, older animals become familiar favorites to frequent zoo visitors. So zoos work hard to find ways to keep them healthy and on view.
A cantankerous 75-year-old cockatoo named Cookie has legions of fans who come to see him at Brookfield Zoo, even as he creakily waddles under an ultraviolet lamp installed in his habitat in an effort to give him enough Vitamin D to treat his osteoporosis. He has been on display at the zoo since it opened.
Geriatric animal problems often mean keepers have to devise entirely new procedures to care for the animals. A seal at Lincoln Park Zoo developed glaucoma and now sees only shapes and shadow, leaving it unable to react to the standard hand signals used by keepers to feed and handle the animals. The blind seal now takes voice cues.
"When animals go blind we make sure we don't change physical details of their habitat that could cause accidents," said Gamble, chief of the zoo's veterinary services. "If they live with other animals, keepers have to watch social behaviors and dynamics closely, because when an animal within a group grows weak or disabled, other animals might ostracize or abuse them. They are in zoos, but they are wild, and wild animals are competitive."
Marta's indoor habitat doesn't look much different from others in the lion house, but keepers have made some subtle changes to help Marta. They added lower perching shelves, and they have installed a leaning tree trunk she uses as a ramp to climb to higher perches, like adding hand rails in the hallways of human geriatric wards.
"We put out an orthopedic pad where she always lands as she jumps down from the perch," said Dave Bernier, the zoo's curator of mammals. "She enjoys the pad, so that is where you often see her lying and resting."
Marta's first serious health problems appeared several years ago when she developed multiple allergies, including to grass, soil and all of her foods, not to mention molds and dust mites. The zoo moved her permanently indoors where they can better manage her environment.
Still, no matter how clean the zoo keeps her area, each winter the building's heating system distributes dust particles and other tiny allergens that set off itchy skin eruptions where Marta's hair falls out. It's unsightly but not serious, keepers say.
"When it gets warm outside and those irritations stop, her fur grows back just fine," said Gamble.
Keepers also had to figure out what to feed her, since she is now allergic to everything zoo leopards normally eat.
Instead of beef and pork, Marta now chews on a mixture of venison and green peas, processed to the consistency of pate. "Venison is a foreign protein to her, and so is duck and rabbit meat, which she can also eat," said Gamble.
But her specialty diet poses another problem in that she can't chew bones, which is how cats normally clean plaque off their teeth. Venison bones carry a risk of transmitting chronic wasting disease, and she is allergic to other kinds. Without clean teeth, Marta risks serious infections.
That is why she gets a thorough cleaning during her annual checkup, including the bubble-gum flavored toothpaste.
"You can get tuna and seafood flavored toothpastes for animals," said Gamble, "but we don't want to take the chance that they might have proteins that could set off her allergies."
Often, so little is known about the life cycles of exotic zoo animals that veterinarians have to improvise. They watch for medical procedures and medicines that were developed for pet and livestock veterinary medicine but might apply to zoo species. The vets even look to human medicine for guidance.
Thomas Meehan, chief veterinarian at Brookfield Zoo, said one of the zoo's gorillas, named Beta, was suffering at age 47 from a fibroid uterine mass that caused abdominal discomfort and heavy vaginal bleeding.
"At her age, we were reluctant to do a hysterectomy on her," said Meehan, because major surgery posed a health threat of its own. After consulting with human doctors, officials elected to do a procedure they said previously had been documented only in people.
Doctors inserted a catheter into the gorilla's left arm and guided it to the uterine artery feeding the fibroid mass. They then plugged the portion feeding the mass, cutting off its blood supply. Since the operation the bleeding has stopped and the mass dramatically shrunk, said Meehan.
Gamble is similarly worried about Marta the leopard. A 2007 physical revealed a mass of tissue in the cat's nostrils, and it had grown considerably by the time of this year's examination.
Marta is too old and weak to withstand surgery and radiation to remove or shrink the growth, Gamble said, but if it continues to grow the leopard will be in dire peril.
"Cats must be able to smell in order to eat," she said. "If they don't have that ability, they simply don't eat and begin to waste away.
"If we're dealing with things that there are no cures for, we try to explain to keepers the possible timelines in the deterioration of an animal's well-being. They will see when the animal is in a lot of discomfort that we are no longer able to treat. At that point it is best to euthanize the animal."