jaribas
23rd February 2010, 12:42
One of the rarest whales in the world was not a victim of extensive whaling as previously supposed.
Fewer than 350 North Atlantic right whales remain, with the blame for their demise laid at the harpoon tips of 16th and 17th century whalers.
But a new study of ancient whale bones confirms the population of northern right whales has for centuries been small with a limited genetic diversity.
That strongly suggests a mass cull of the animals never took place.
"This is a big surprise given what was previously thought about the species," says Dr Brenna McLeod, previously at Trent University in Peterborough, Ontario, Canada, who has published the latest study in the journal Conservation Genetics.
The North Atlantic right whale (Eubalaena glacialis) has typically been perceived as a species that was once abundant and successful in the ocean that gave it its name.
Then it was assumed that 16th century Basque whalers decimated the population, with American whalers that followed further reducing the small remaining numbers, explains Dr McLeod, now at Saint Mary's University in Halifax, Nova Scotia.
That left the approximately 300 to 350 individuals that remain today.
However, the discovery in 1978 of a 16th century Basque whaling galleon by historian Dr Selma Barkham offered a way to check these assumptions.
Within that ship lay whale bones, which after years of excavation were brought to the surface.
One researcher, Dr Moira Brown, now at the New England Aquarium in Boston, US realised that if DNA could be extracted from these bones, it could reveal a host of information about the culled whales.
In earlier research, Dr McLeod, Dr Brown and colleagues managed to do just that.
They extracted DNA from 218 whale bones recovered from either the galleon or from the shores of Quebec and Labrador, whey they had been lying for 400 years at sites of long-forgotten Basque whaling stations.
Of those bones, just one came from a North Atlantic right whale, the others all coming from bowhead whales.
"There was absolutely no evidence of a right whale targeted hunt," Dr McLeod told the BBC.
In their latest study, the researchers then attempted to glean more information from this single 400-year-old North Atlantic right whale bone.
"This single bone provides us with a snapshot of the genetic characteristics of the historic population," says Dr McLeod.
By sampling 27 different parts of the bone's DNA, the researchers could evaluate the number of variations within its genetic code. Called alleles, such variations may have been carried by historic North Atlantic right whales, but have since disappeared from today's population.
The greater the collapse in the population of North Atlantic right whales, the more of these genetic variations would be lost.
Yet "we found no 'lost' alleles," says Dr McLeod.
"All that were identified are still present in the contemporary population."
The researchers also found that the overall genetic profiles of the ancient bone and those from modern North Atlantic right whales are very similar.
"This would not have been expected if the population had lost a lot of variation as a result of a large reduction in population size due to whaling," says Dr McLeod.
In short, the North Atlantic right whale population of the past was little different to today.
"Whaling did affect the species, by reducing the population size, but not nearly to the extent that was thought," says Dr McLeod.
"Instead of numbering in the 12,000 to 15,000 as was previously assumed and suggested, we think that the population in the western north Atlantic was much smaller, perhaps numbering a few thousand."
The jury is still out as to what caused the original crash in North Atlantic right whale numbers, reducing them to this level.
North Atlantic right whales tend to live near the coast.
"We speculate that the species may have been affected by historic climatic changes, such as glaciation events, which may have caused the species to shift its habitat.
"This would have altered the location and availability of feeding and calving grounds and may have affected fitness and reproductive success of individuals in the population," explains Dr McLeod.
The new finding also casts a new perspective on efforts to save this highly endangered whale.
Today the whale's recovery is hampered because individuals are being struck by ships or entangled in fishing gear.
Recent climatic changes are also preventing the whales from reproducing as fast.
But while everything should be done to prevent whales killed accidently by ships and fishermen, "in light of the data presented here, some of the conditions that are challenging recovery of the right whale have been present for thousands of years, far longer than we have thought," says Dr McLeod.
So although the surviving population may be critically small, it may be adapted to cope with many of the natural changes it faces today.
Fewer than 350 North Atlantic right whales remain, with the blame for their demise laid at the harpoon tips of 16th and 17th century whalers.
But a new study of ancient whale bones confirms the population of northern right whales has for centuries been small with a limited genetic diversity.
That strongly suggests a mass cull of the animals never took place.
"This is a big surprise given what was previously thought about the species," says Dr Brenna McLeod, previously at Trent University in Peterborough, Ontario, Canada, who has published the latest study in the journal Conservation Genetics.
The North Atlantic right whale (Eubalaena glacialis) has typically been perceived as a species that was once abundant and successful in the ocean that gave it its name.
Then it was assumed that 16th century Basque whalers decimated the population, with American whalers that followed further reducing the small remaining numbers, explains Dr McLeod, now at Saint Mary's University in Halifax, Nova Scotia.
That left the approximately 300 to 350 individuals that remain today.
However, the discovery in 1978 of a 16th century Basque whaling galleon by historian Dr Selma Barkham offered a way to check these assumptions.
Within that ship lay whale bones, which after years of excavation were brought to the surface.
One researcher, Dr Moira Brown, now at the New England Aquarium in Boston, US realised that if DNA could be extracted from these bones, it could reveal a host of information about the culled whales.
In earlier research, Dr McLeod, Dr Brown and colleagues managed to do just that.
They extracted DNA from 218 whale bones recovered from either the galleon or from the shores of Quebec and Labrador, whey they had been lying for 400 years at sites of long-forgotten Basque whaling stations.
Of those bones, just one came from a North Atlantic right whale, the others all coming from bowhead whales.
"There was absolutely no evidence of a right whale targeted hunt," Dr McLeod told the BBC.
In their latest study, the researchers then attempted to glean more information from this single 400-year-old North Atlantic right whale bone.
"This single bone provides us with a snapshot of the genetic characteristics of the historic population," says Dr McLeod.
By sampling 27 different parts of the bone's DNA, the researchers could evaluate the number of variations within its genetic code. Called alleles, such variations may have been carried by historic North Atlantic right whales, but have since disappeared from today's population.
The greater the collapse in the population of North Atlantic right whales, the more of these genetic variations would be lost.
Yet "we found no 'lost' alleles," says Dr McLeod.
"All that were identified are still present in the contemporary population."
The researchers also found that the overall genetic profiles of the ancient bone and those from modern North Atlantic right whales are very similar.
"This would not have been expected if the population had lost a lot of variation as a result of a large reduction in population size due to whaling," says Dr McLeod.
In short, the North Atlantic right whale population of the past was little different to today.
"Whaling did affect the species, by reducing the population size, but not nearly to the extent that was thought," says Dr McLeod.
"Instead of numbering in the 12,000 to 15,000 as was previously assumed and suggested, we think that the population in the western north Atlantic was much smaller, perhaps numbering a few thousand."
The jury is still out as to what caused the original crash in North Atlantic right whale numbers, reducing them to this level.
North Atlantic right whales tend to live near the coast.
"We speculate that the species may have been affected by historic climatic changes, such as glaciation events, which may have caused the species to shift its habitat.
"This would have altered the location and availability of feeding and calving grounds and may have affected fitness and reproductive success of individuals in the population," explains Dr McLeod.
The new finding also casts a new perspective on efforts to save this highly endangered whale.
Today the whale's recovery is hampered because individuals are being struck by ships or entangled in fishing gear.
Recent climatic changes are also preventing the whales from reproducing as fast.
But while everything should be done to prevent whales killed accidently by ships and fishermen, "in light of the data presented here, some of the conditions that are challenging recovery of the right whale have been present for thousands of years, far longer than we have thought," says Dr McLeod.
So although the surviving population may be critically small, it may be adapted to cope with many of the natural changes it faces today.