Short-finned pilot whales are officially composed of two distinct subspecies, according to new research which has proved a 250-year-old theory correct.

Back in 1760, a Japanese naturalist called Yamase first described two different types of short-finned pilot whales. He called whales with square-shaped heads in southern Japan the “Naisa form” and the round-head variety in northern Japan the “Shiho form”.

Now using the latest DNA tests scientists have found Yamase was correct.

Lead researcher Amy Van Cise, a postdoctoral scholar at the Woods Hole Oceanographic Institution in Massachusetts told The Independent: “There’s been a growing amount of data since the eighties showing this so it was just a case of locking it down and showing it was true.”

Dr Cise and her team analysed 725 samples collected by researchers from all over the world and tested their mitochondrial DNA. By comparing this information with known whales and dolphins, researchers could identify that the groups were subspecies, according to the study published in Molecular Ecology.

Tragic photos show beached whales Show all 15 1 /15 Tragic photos show beached whales Tragic photos show beached whales A dead sperm whale lies on Hunstanton beach in Norfolk on 5 February 2016 AFP/Getty Tragic photos show beached whales Volunteers pour buckets of water over the 80 remaining live pilot whales found stranded on remote Ocean Beach on New Zealand's southern-most Stewart island, 8 January 2003 AFP/Getty Tragic photos show beached whales Contractors clear away the body of one of the dead 48ft sperm whales that were washed-up on a beach near Gibraltar Point in Skegness, Lincolnshire in 2016 PA Tragic photos show beached whales People pass by a beached whale at the Pointe de la Torche, near Brest in France on 29 November 2011 AFP/Getty Tragic photos show beached whales A woman touches the tail of a large whale carcass on Wattamola Beach at the Royal National Park in Sydney on 25 September 2018 AFP/Getty Tragic photos show beached whales Beached humpback whale in California, 2015 AFP/Getty Tragic photos show beached whales Dead long fin pilot whales at Hamelin Bay on Australia's west coast on 23 March 2009 AFP/Getty Tragic photos show beached whales A 36ft sperm whale lies dead on the beach at Sutton Bridge, in The Wash, off the Lincolnshire coast, where it became stranded in 2004 PA Tragic photos show beached whales A female fin whale opens its mouth as it lies stranded and alive on the beach at Carlyon Bay, Cornwall on 13 August 2012 Getty Tragic photos show beached whales The lower jaw of a dead sperm whale that stranded itself on a beach in Hunstanton, Norfolk on 5 February 2016 Getty Tragic photos show beached whales One of the five sperm whales that were found washed ashore on beaches near Skegness, Lincolnshire over the weekend on 25 January 2016 Getty Tragic photos show beached whales Employees at work to skin the remains of a beached 60ft whale on 25 January 2013 AFP/Getty Tragic photos show beached whales Two long-finned pilot whales are stranded on a beach in the northern French city of Calais on 2 November 2015 AFP/Getty Tragic photos show beached whales A sperm whale lies dead after becoming stranded on a beach in Hunstanton, Norfolk on 5 February 2016 Getty Tragic photos show beached whales Crowds gather as a sperm whale lies dead after becoming stranded on a beach in Hunstanton, Norfolk on 5 February 2016 Getty

“Most of the samples were collected by biopsies, some were collected from animals that were stranded and a fewer number were collected from whales caught in native hunts. We collected this data thanks to a large international collaboration”, she said.

What is particularly remarkable about the finding is that the whales are not separated by a continental barrier but just the vast expanse of the eastern Pacific Ocean.

Whales living off northern Japan and the eastern Pacific are a single distinct subspecies (Natalie Renier, Woods Hole Oceanographic Institution)

“You would expect to see a different subspecies of whale in each ocean basin—the Atlantic, Indian, and Pacific. That’s pretty common. But what we found was that short-finned pilot whales in the Atlantic are the same sub-species as those living in the Indian Ocean and western Pacific,” said Dr Van Cise.

“Whales living off northern Japan and the eastern Pacific, however, seemed to be a single distinct subspecies.”

“It seems to have separated these groups of whales for long enough that they diverged into two different types. That means continents and land forms may not have been as significant a barrier as we thought to this species’ evolution. Instead, the oceanic ‘desert’ in the Pacific might have been more important,” said Dr Van Cise.

Short-finned pilot whales are found all over the world, with habitats in the Indian, Pacific, and North Atlantic oceans.

“You can’t manage animals globally without understanding their diversity. If you think of a group of animals as a single species, and it turns out they’re not, you could wind up accidentally losing an entire subspecies without knowing it,” said Dr Van Cise.

“We don’t know very much about their feeding behaviour in general so we can’t say very much about their differences. In terms of behaviour they might mate at different times of the year. We know very little about pilot whales full stop.”