Steven Austad, of the Barshop Institute for Longevity and Aging Studies, at the University of Texas Health Science Center at San Antonio, has applied the longevity quotient—which he developed—to many species, including those depicted here. The quotient is determined by dividing the greatest recorded longevity for a species by the life span that would be expected based on the species's average weight. Except for humans and Brandt's bat, the scores refer to animals in captivity.
The white-eared opossum has a longevity quotient of 0.3, making it unusually short-lived for its size.
The Asian house shrew has a 0.4 longevity quotient, and like the white-eared opossum, has and unusually short life span relative to other mammals of its size.
The typical laboratory mouse, also known as the house mouse, has a short lifetime, reflected in its longevity quotient of 0.5.
The giraffe may look odd but its life span is typical for a mammal its size; it has a 1.0 longevity quotient.
Like giraffes, the African lion lives about as long as would be expected for its size. Its longevity quotient is 1.1.
The southern flying squirrel has a 2.7 longevity quotient, which means it is unusually long-lived.
The vampire bat, with a longevity quotient of 3.5, also lives an unusually long time.
We humans have a longevity quotient of 5.0, a sign that we generally live longer than would be expected for our size. Jeanne Calment (pictured) died at age 122, having outlived anyone else whose age at death has been well documented.
The naked mole-rat's longevity quotient is 5.3; it is a very long-lived small mammal.
The life span of Brandt's bat is exceptional; it has a longevity quotient of 9.8.