eli5: How do we know different organisms lifespans?

Question

Have we kept them all in captivity at one point? Are all lifespans a guess from scientists? A general estimate?

In: 10

Answer 1

Pretty much, almost every animal has been tracked, not necessarily in captivity, but in the wild by some biologist. Although many are estimates, in nature it’s very rare for animals to die of old age, they pretty much all die of disease, starvation, predation, injury, or severe weather