January 6, 2010

Two Types Of Killer Whales In UK Waters

Scientists are now saying that there are actually two types of killer whales living in UK waters instead of just one, as was previously thought, according to BBC News.

The whales are different from each other in both the way they look and the way they eat, and the males of one type are about 6-feet longer than the other.

Researchers believe the killer whales could be at an early stage of becoming two separate species.

The findings have been published by the international group of scientists in the journal Molecular Ecology.

"It's exciting to think about two very different types of killer whale in the waters around Britain," says Dr. Andy Foote from the University of Aberdeen, UK, who took on the study.

"Killer whales aren't really a species that we think of as being a regular visitor to Britain, but in fact we have two forms of these killer whales in our waters," he told the BBC.

Scientists have discovered different forms of killer whales that fill certain roles in the ecosystem in the Pacific and the Antarctic, but they have never before been witnessed in the North Atlantic.

Foote took on the research with colleagues from universities and museums in Denmark and the UK.

Also referred to as orcas (Orcinus orca), Killer whales live in family groups called pods.
They are the most massive member of the dolphin family, and are also known for their high level of intelligence and broad range of hunting behaviors.

There was very little information prior to this study to suggest that different types of killer whale would be found in the North Atlantic.

However, Foote and his colleagues examined the teeth of killer whale remains found over the past 200 years and found a difference in the way the teeth had been worn down.

"We found that one form, which we call 'type 1' had severely worn teeth in all adult specimens," explained Foote.

"The other form, 'type 2', had virtually no tooth wear even in the largest adults."

The killer whales in the wild that "suck up" herring and mackerel have this type of tooth wear.

With this information, the researchers have reason to believe that there must be a difference in the diet and ecological role between the two types.

By using stable isotope analysis that provides clues to the orcas' diet, the scientists determined that type 1 is a generalist feeder, consuming fish and seals. Type 2, on the other hand, is a specialist feeder that scientists suspect subsists only on marine mammals like small dolphins and whales.

The different ecological niches have also caused the two types of killer whales to differ in shape and appearance. 

"The two types also differed in length, with type 2 adult males being almost two yards larger than types 1 males," Dr Foote says.

The scientists also observed that color, pattern and number of teeth vary between the groups.

According to Foote, the fish feeding type 1 killer whales are found across the North East Atlantic and around Britain.

The type 2 killer whales, that feed on cetacean mammals, are regularly seen off the west coast of Scotland and Ireland.

Genetic analysis suggests that the two types belong to two different populations.

"Type 1 specimens were from closely related populations, but the type 2 whales were more closely related to a group of Antarctic killer whales," Foote explained.

A comparison of findings with studies on killer whales across the globe reveal that killer whales have radiated to fill different ecological roles.

"It's similar to how Darwin's finches have adapted to different ecological roles in the Galapagos, but on a larger scale," Foote said.

He noted that this could be a vital discovery for the future of the animals.

"They seem to have occupied completely different ecological niches and have started to diverge morphologically. This divergence may eventually lead to the two types becoming different species."

He went on to advise that the two types be considered "evolutionary significant units" and watched separately in order to more effectively conserve one of the oceans most fascinating creatures.


On the Net: