(Photo credit: Els Vermeulen/University of Pretoria (CC BY-NC-ND))
Research shows that critically endangered southern right whales may live twice as long as previously thought. These whales often live to be 130 years old, and in some cases, 150 years old, according to new data.
Southern right whales (Eubalaena australis) are found throughout the Southern Hemisphere, but were heavily hunted until the 1960s, when the International Whaling Commission began to impose restrictions on commercial whaling. The whaling industry considered these whales the “right” species to hunt because of their slow movement, ability to float after death, and significant quantities of valuable blubber and baleen.
Previously, researchers believed that southern right whales lived for about 70 years. However, these marine mammals are closely related to bowhead whales, and the longest-living known mammal is the Alaskan bowhead whale (Balaena mysticetus), whose age is estimated at 211 years.
“Given everything we knew about the life history of these species, I assumed they [southern right whales] should have longer lifespans,” study co-author Greg Breed, a quantitative ecologist at the University of Alaska Fairbanks, told Live Science.
However, estimating the lifespan of whales can be difficult.
Researchers typically analyze the growth rings on teeth, which form each year like tree rings. However, many baleen whales may lack these layers. Even if they do, tissue wear and a lack of samples can skew the results.
The bigger problem, however, is that commercial whaling ceased only about 60 years ago. So whales older than that may have survived many decades of active whaling and become long-lived. It is likely that only a few individuals reached their full lifespan.
To overcome these challenges, Breed and his team analyzed tracking data from both southern and North Atlantic right whales (Eubalaena glacialis) collected over four decades. From 1979 to 2021, scientists led by Peter Best of the University of Pretoria in Cape Town studied female southern right whales off the southern coast of Africa, photographing them annually. During that study, the researchers involved in the new research identified 2,476 females, 139 of which had a known birth year. Breed and his team used that data to construct a survival curve, noting the age and rate at which individuals disappear from the population. From this, they were able to estimate what proportion of the population survives to a given age.
“It's similar to how the Social Security Administration determines how long a person who is 65 years old today will live on average from now on, rather than from the time they were born,” Breed said.
The researchers compared these results with records of North Atlantic right whales collected around the same time and provided by the North Atlantic Right Whale Consortium, a non-profit conservation organization.
The analysis, described in a study published Dec. 20 in the journal Science Advances, found that southern right whales have an average lifespan of 70 to 75 years. Projections indicate that one in 10 individuals will live past 130, supporting Breed’s original hypothesis. In contrast, North Atlantic right whales have relatively short lifespans — an average of 22 years, with only a few surviving past 45.
“It’s not because they’re biologically very different, it’s because they’re subject to a much higher rate of anthropogenic or man-made mortality than southern right whales,” Breed said. North Atlantic right whales are often entangled in fishing gear, especially lobster and crab pots, which are fixed
Sourse: www.livescience.com
