What is the secret to a long life?S

Early longevity studies led scientists to the conclusion that a creature's lifespan was proportional to its body mass and heart rate; "the big, slow elephant outlives the quick, small mouse," explains Fred Guterl in a recent piece for Scientific American.

But small, long-lived organisms like naked mole rats (which can live up to 28 years — literally decades longer than other rodents), birds and bats are shifting (and complicating) our understanding of longevity. This infographic compares the record-setting lifespans of ten organisms, and the various biological factors scientists think may have a hand in prolonging life.

According to Guterl, the hot new biological barometer for gauging an organism's lifespan is its total energy output.

What is the secret to a long life?S

"When scientists look within particular species, size does not correlate well with life span," he explains, "although fast growth is often associated with reduced longevity."

Looking at this infographic (you'll need to click it to enlarge and compare the characteristics illustrated in the bottom right hand corner of the visualization), borrowed from Guterl's post, it's interesting to note the huge variations in relative body mass and estimated lifetime heartbeats relative to the organisms' lifespans, and underscores how complicated it is to relate specific biological factors to a something like an organism's longevity.

"To some degree, resting metabolic rate does correlate, but for animals total energy expended over a lifetime may be the best indicator of all."

Read more, and check out an interactive version of the infographic, over at SciAm.