Gray's beaked whales have been stable for over a million years

A study from the University of Exeter is shedding new light on an elusive whale species in the Southern Ocean. The experts report that Gray’s beaked whales appear to be resilient to ecosystem changes and human activities, and have maintained a stable population for more than a million years.

Gray’s beaked whales live in the deep oceans of the Southern Hemisphere and are rarely spotted. Prior to this study, the biology of the whales was almost entirely a mystery.

Gray’s beaked whales are small whales that spend most of their time deep below the ocean’s surface feeding on squid. Observational data on the species is impossible to obtain. Whalers refer to them as “scamperdown whales” due to their evasive behavior.

In collaboration with experts at the University of Copenhagen, the Exeter team set out to investigate the history of the population over the past 1.1 million years. The researchers analyzed the genome sequences of 22 Gray’s beaked whales that were previously stranded on beaches in South Africa, Australia, and New Zealand 

“The population approximately doubled about 250 thousand years ago, coinciding with a period of increased Southern Ocean productivity, sea surface temperature and a potential expansion of suitable habitat,” study co-author Dr. Kirsten Thompson.

According to the genetic analysis, the current population appears to have high levels of genetic diversity and no patterns of genetic similarity in geographical areas. This indicates that the whales leave their birth groups and move widely throughout their range across the Southern Hemisphere.

Based on their high levels of genetic diversity, a flexible social system, and the rich habitats of the Southern Hemisphere, the experts believe that Gray’s beaked whales could be resilient to changing ecosystem conditions.

“Human activity is causing rapid ecological change in every habitat on Earth, including the deep oceans,” said Dr Thompson. “We need to understand how different species might respond to these changes, but we lack detailed knowledge on many animals, particularly deep-sea whales like Gray’s beaked whales.”

The experts used mitochondrial DNA to investigate the history of the population and partial nuclear genomes to estimate population structure.

“Our findings suggest the numbers of Gray’s beaked whales have been relatively stable for the last 1.1 million years,” said Dr.  Thompson.

“The Southern Hemisphere’s oceans could potentially support a surprisingly large number of Gray’s beaked whales. Good news for one species at least.”

“We show how genomic tools can help to reveal past history, current status and potential near-future changes in animal populations that are enigmatic, rarely observed and beyond the reach of traditional boat surveys.”

The study is published in the journal Royal Society Open Science.

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By Chrissy Sexton, Earth.com Staff Writer