Whales are not only the largest animals on Earth, they are also among the longest-lived. A new analysis shows that right whales can live more than 130 years, nearly twice as long as previously thought. Right whales are filter-feeding baleen whales that were hunted almost to extinction during the heyday of the whaling industry. As a result, some of the most basic information about them remains unknown, including how long they live.
To answer some of these questions, researchers at the University of Alaska Fairbanks analyzed 40 years of data collected by the Right Whale Identification Project. The research focused on two species: Southern right whales, which live in the oceans around Antarctica, Australia, South America and South Africa; and North Atlantic right whales, which live along the east coast of the United States and the northwestern edge of Europe.
The team used the data to create so-called survival curves, which plot how many individuals survive at each age. This can be used to infer the average age and possible maximum lifespan of a population.
It has long been thought that these two species of right whales only live to be 70 to 75 years old at most, but new research finds that they live much longer. It has been calculated that the median lifespan of southern right whales is about 73 years, and more than 10% of right whales are expected to live longer than 132 years.
Unfortunately, things are not looking good for North Atlantic right whales. Their median lifespan is only 22 years, and 10% live longer than 47 years.
Greg Breed, lead author of the study, said: "North Atlantic whales have unusually short lifespans compared to other whales, but that's not because of inherent differences in biology that mean they should live longer. They often get entangled in fishing gear or are struck by ships, and they suffer from starvation, which may be related to environmental changes that we don't fully understand yet."
The team cited similar reasons for underestimating the maximum lifespan of both species of right whales. Biologically, there should be very old individuals in both populations, but as the team points out, whaling only ended about 60 years ago, meaning the oldest animals must have withstood threats from humans in the 40 years before that.
"We didn't know how to measure the age of baleen whales until 1955, which was the end of industrial whaling," Breed said. "By the time we figured it out, there weren't many old whales left to study. So we just assumed they didn't live that long."
It is important to understand the aging process in animals such as whales at both the individual and group levels. Older members of the group teach important survival skills to younger generations, so losing these mentors affects the recovery of the entire species. For whales, a species with a slow reproductive cycle, recovery is already a long process.
The research was published in the journal Science Advances.