Reaching ages over 60 years, chimpanzees are one of the few animals that approach human longevity. While we've long viewed old age in humans as unique, a recent study shows that the difference between human and chimpanzee lifespans is smaller than previously thought (Wood et al., 2016).
Here in Kibale National Park, my research on the Ngogo chimpanzees focuses on old age and asks why they have such extended lifespans. Here are a few photos of these wizened warriors from this past week.
Dexter (b. 1985). Old yet? Not quite. Dexter is 32, which would be old for many primates, but not chimps who stay in their prime until ~30. Still, Dexter might be exploring early retirement for he is known for taking frequent naps.
Garrison (b. 1977). One of the highest ranking males in the West, 40 year old Garrison here is groomed by Buckner (b. 1999)
Monk (b. 1972). The grizzled warrior, you can spot Monk's scar on his upper lip. Monk comes from a legacy family of high ranking chimpanzees. Pictured here groomed by younger male, Hicks (b. 1997). Check out his mom, Garbo, below.
Garbo (b. 1956). A practical matriarch, at 61 Garbo is still a social butterfly. She travels and even patrols with her sons, including Monk.
How do you know how old they are?
Researchers began to follow these chimpanzees regularly only in 1995, so ages for individuals older than this are estimated using data like reproductive behavior and appearance. Check out the Wood et al. article below for info on age estimations.
What's the oldest chimpanzee at Ngogo?
That prize currently goes to Marelene (b. 1950) with a close second Harper (b. 1952).
Do females live longer than males?
Yes, females have a much older life expectancy than males. In the top 10 oldest individuals at Ngogo, there is only one male (Brownface b. 1966). Check out my earlier post on hunting for a photo of him.
Do females chimpanzees experience menopause?
Many wild female chimpanzees experience a short post-reproductive lifespan (perhaps about 1/4) , which means that they stop giving birth to young, or even being able to conceive. In a study that examined the fertility and mortality patterns across six wild populations, Emery Thompson et al. (2007) found that chimpanzee and human birth rates show similar patterns of decline beginning in the fourth decade. Menopause was once thought to be uniquely human, but this is now up for debate with evidence among chimpanzees and whales as well.
Emery Thompson, M., Jones, J. H., Pusey, A. E., Brewer-Marsden, S., Goodall, J., Marsden, D., … Wrangham, R. W. (2007). Aging and Fertility Patterns in Wild Chimpanzees Provide Insights into the Evolution of Menopause. Current Biology, 17(24), 2150–2156. http://doi.org/10.1016/j.cub.2007.11.033
Wood, B. M., Watts, D. P., Mitani, J. C., & Langergraber, K. E. (2016). Favorable ecological circumstances promote life expectancy in chimpanzees similar to that of human hunter-gatherers. Journal of Human Evolution, 105, 41–56. http://doi.org/10.1016/j.jhevol.2017.01.003
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