This Sunday marked the third birthday for African lion, Sahar. Beyond giving our staff and visitors something fun to celebrate, the special occasion also highlighted how Lincoln Park Zoo has led the way in developing a new understanding of the animals in our care.
Sahar's third birthday offers a chance to share how much zoos have learned about animal longevity. Photo by Anthony Nielsen.
Whenever we discuss animal birthdays, a common question is “How long does that animal live?” For a long time, zoos didn’t have firm answers to that question. We could reference the longest-lived individual in our record books, but that would be like saying humans live to be 122. Just because one person has done it doesn’t mean it’s a representative life span for our species.
A more useful way of determining how long an individual is likely to live is to calculate the median life expectancy. How is it determined? You list the lifespan for every individual in a population. Then you identify the midway point in that spread—the age where just as many individuals continue to live as have died. That’s the median life expectancy for that species.
With support from the Columbus Zoo and Aquarium, scientists at Lincoln Park Zoo and the Associations of Zoos and Aquariums Population Management Center have calculated median life expectancies for many high-profile species in AZA-accredited zoos and aquariums. For African lions, like Sahar, the median life expectancy is 16.8 years. Chimpanzee Keo, the oldest living male chimpanzee in a North American zoo, will turn 55 this July, putting him well past the male chimpanzee median life expectancy of 31.7 years. (The excellent geriatric care zoos now provide means that animals are living longer than ever.)
Individual circumstances always vary, but these numbers give us a scientific way to talk about survival, from Bactrian camels (17.8 years) to Pallas’ cats (8.6 years), Chilean flamingos (27.8 years), Bolivian gray titi monkeys (11.7 years) and more. These life expectancies can also help us apply some context to loss.
After all, regardless of our species, we all pass eventually. The median life expectancy for people in the United States is 78.7 years. Some will live longer, some will live less, but few of us will make it to 122! The same is true for animals, even as zoos continue to learn—and provide the best possible care.