As the companion of a geriatric cat, I am acutely conscious of the changes in nutritional, psychological and medical care that must be afforded to aging animals. With advancements in veterinary science and safer environments, just as domestic pets in affluent nations are experiencing unprecedented increase in their longevity, so are the inmates of modern, better designed zoos. As a result, zoo animals sometimes survive much longer than they might in their natural habitats. Older animals in zoos offer up new challenges to their care takers who must learn to adapt to the changing and sometimes unexpected needs of their aging wards.
Even as a youngster, Rollie looked older and wiser than his years. His white mustache sprouted longer by the month, until it flamed from his cheeks like a German kaiser's. In the past few years, though, the tribulations of age — not just the appearance of it — have begun catching up with Rollie. His keepers are reminded each time they get a look past the Emperor Tamarin's flowing whiskers and into his jaws. The monkey, used to crunching on raw sweet potato, has surrendered all but six of his 32 teeth to the toll of time. At 17, Rollie — a resident of Chicago's Lincoln Park Zoo — is a senior citizen of his species. In the Amazon he almost certainly would never have made it this long. In captivity, he's got plenty of company.
The golden years have arrived at the nation's zoos and aquariums, taking veterinarians and keepers, along with their animals, into a zone of unknowns.
Do female gorillas, living in to their 40s and 50s, experience menopause?
Can an aging lemur suffer from dementia?
How do you weigh the most difficult choice — between prolonging pain and ending life — when the patient is a venerable jaguar who feels like a member of the family?
All those questions hang on a larger one that, until recent years, has been left to educated guesswork.
"How old do animals really live?" says Sharon Dewar, a spokeswoman for the Lincoln Park Zoo, whose keepers adjusted to Rollie's toothlessness by serving him soft-cooked veggies. "That's the million-dollar question."
Zeroing in on the answer takes years of tracking births, deaths and the age of animal populations. But zoos, which have pooled information since the 1970s, are drawing conclusions. For example, records show that the median age of Siberian tigers in zoos has reached 15 years old, up from just over 11 in the two decades ending in 1990.
Russ Williams, the executive director of the North Carolina Zoo Society ponders the same questions on his blog.