Whales - the senior citizens of our global seas

With a recent study claiming right-whales are capable of lifespans stretching beyond 150 years, double what was previously thought, it would be poetic to imagine that some of these great cetaceans swimming today were alive when Herman Melville wrote Moby Dick in 1851. Yet, in truth, few older whales remain since their industrialised slaughter intensified during the early 20th century. Thus, this latest research published by the University of Alaska Fairbanks relied on modelling data of recent sightings to reinterpret the lifespans of Southern and North Atlantic right whales.

Published in the journal Science Advances, the lead author, Gary Breed, an associate professor, calculated that Southern right whales potentially live well past 100 years, with 10% of their population achieving 130 years and some one hundred and fifty. These findings go well beyond a previous assumption that these large baleens had a life expectancy between 70 and 80 years. They calculated the current southern right median age to be 73.

Previously, estimations of a whale’s age came via studying dead specimens by either assessing the chemical transformation of proteins in the eye or earwax rings, which increase year-on-year. This new non-lethal research used 40 years of photo-identification sightings collated by other researchers of right-whales dating back to the 1970s. Females were analysed, and when they stopped being found in the photographic record, they were assumed to have died. Data plotted on a graph thereafter called a ‘survivorship curve’ allowed the team - via complex mathematical survival models well above my pay grade - to extrapolate potential longevity without actually sighting actual older whales.

“These animals live longer than we thought, and old individuals are likely missing because of a history of whaling,” Breed told explorearth.com. “Imagine if you measured the ages of a population of people but never found any individuals over age 45.  You might conclude that humans simply don’t live past 45.  However, suppose a mass mortality event happened 50 years before that wiped out almost everyone. What might actually be happening is that the entire population was simply born after the mass mortality event. So, although humans can reach 90 years of age, everyone in the population is still less than 50. And if you’re a species that actually can live to be 150, it will take a very long time for a normal amount of old individuals to reappear”.