Some whales may live nearly twice as long as believed—if we let them

Study extends lifespan estimate for one whale species and suggests researchers have been underestimating others as well

||| FROM SCIENCE.ORG |||

Among mammals, whales are the longevity champs. Members of several species have lived past age 100, and one bowhead whale reached its 211th birthday. But estimates of whale longevity often require scarce tissue samples and can rely on techniques that are difficult to interpret.

A study published today in Science Advances may have found a better way. By combining decadeslong photo records with the same statistical approach companies use to set life insurance rates, scientists have deduced that at least one species of whale survives almost twice as long as researchers expected. Other whales may beat longevity predictions, too, the work suggests.

“What the authors have done here is quite impressive,” says marine mammal biologist C. Scott Baker of Oregon State University, who wasn’t connected to the study. “They make a good case for the plausibility of their results.”

Researchers have used several methods to try to gauge whales’ ages, such as counting the layers in their earwax, which stack up year after year like tree rings, and measuring a chemical transformation in eye proteins that occurs at a regular rate. Scientists have also drawn on historical evidence—the harpoon tips embedded in the animals’ blubber.

These data suggest the bowhead whale (Balaena mysticetus)—a plankton-feeder that lives in the Arctic—leads the pod in longevity. But a number of other species can breach 100 years, including blue, fin, and beluga whales.

However, the samples for these analyses—which often require freshly deceased animals—can be hard to obtain and aging methods such as earwax accumulation don’t work for all species. Another complication? Whaling was so intense for several decades in the 20th century that in many species, almost all of the large, old whales were probably slaughtered, says ecologist Greg Breed of the University of Alaska Fairbanks. Most whales alive today are probably relatively young, he says, making it even more difficult to identify any surviving oldsters.

To overcome these limitations, Breed and colleagues used statistical analysis to estimate the lifespans of two species of right whale, the North Atlantic right whale (Eubalaena glacialis) and the southern right whale (Eubalaena australis)—both of which had been subjected to intensive whaling in the past. Instead of samples from dead whales, the team turned to photo catalogs of the two species stretching back to the 1970s. Using these records, researchers can identify individual whales by their appearance and tell when a particular animal vanishes from the population, likely because it has died.

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