Gray's beaked whale - female side view

Gray’s beaked whales 'resilient' to ecosystem changes

An elusive whale species in the Southern Ocean could be resilient to near-future ecosystem changes, according to a new study by the universities of Exeter and Copenhagen.

Gray’s beaked whales living in the deep oceans of the Southern Hemisphere are rarely seen alive and their ecology has remained a mystery to scientists until now.

The study used genome sequencing of 22 whales washed up on beaches in South Africa, Australia and New Zealand to investigate the history of the population over the past 1.1 million years.

Author of the study Dr Kirsten Thompson, of the University of Exeter, said: "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.”

The current population appears to have high levels of genetic diversity and no "genetic structure" (patterns of genetic similarity in geographical areas), suggesting the whales leave their birth groups and move widely throughout their Southern Hemisphere range.

Based on these findings, this perfect match of high genetic diversity, a flexible social system and the rich habitats of Southern Hemisphere mean that Gray’s beaked whales could be to be resilient to changing 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."

Observation data on this species is impossible to obtain – they are small (five metres), deep-diving whales that spend most of their time below the surface searching and feeding on squid – whalers nicknamed them "scamperdown whales" due to their elusive behaviour.

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

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

“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 received funding from the Lerner Grey Memorial Fund for Marine Research of the American Natural History Museum, the University of Exeter European Network Fund, Villum Fonden Young Investigator Programme and the Independent Research Fund Denmark.

The paper, published in the journal Royal Society Open Science, is entitled: "Ocean-wide genomic variation in Gray’s beaked whales, Mesoplodon grayi."

Date: 25 March 2021