by DAVID GARDNER

Last updated at 23:37 13 June 2007

A giant bowhead whale caught off the coast of Alaska had a harpoon point embedded in its neck that showed it survived a similar hunt – more than a century ago.

Biologists claim the find helps prove the bowhead is the oldest living mammal on earth.

They say the 13-centimetre arrow-shaped fragment dates back to around 1880, meaning the 50-ton whale had been coasting around the freezing arctic waters since Victorian times.

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Because traditional whale hunters never took calves, experts estimate the bowhead was several years old when it was first shot and about 130 when it died last month.

"No other finding has been so precise," said John Bockstoce, a curator at the New Bedford Whaling Museum in Massachusetts.

Calculating a bowhead whale's age can be difficult, and is usually gauged by amino acids in the eye lenses.

It is rare to find one that has lived more than a century, but experts now believe the oldest were close to 200 years old.

The weapon fragment lodged in a bone between the whale's neck and shoulder blade comes from a 19th century bomb lance.

Fired from a heavy shoulder gun, the harpoon was attached to a small metal cylinder filled with explosives and fitted with a time fuse so it would explode seconds after it was shot into the whale.

Experts have pinned down the weapons manufacture to a New England factory in about 1880 and say it was rendered obsolete by a less bulky darting gun a few years later.

Even though the device probably exploded, the bowhead was protected by a one foot thick layer of blubber and thick bones it uses to break through ice one foot thick to breathe at the surface.

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"It probably hurt the whale, or annoyed him, but it hit him in a non-lethal place," said Mr Bockstoce.

"He couldn't have been that bothered if he lived for another 100 years."

The find adds growing weight to evidence that bowheads outlive all other mammals.

Six similar harpoon points have been found in the

whales since 2001, all suggesting they live much longer than previously thought.

The oldest known ages for mammals are 110 years for a blue whale and 114 years for a fin whale.

The oldest documented human was a 122-year-old French woman, who died ten years ago.

The only other mammal that comes close is elephants, which can live to 70 in captivity.

Scientists believe that the bowheads' longevity is the result of the tough environment where they live in the freezing arctic, where there are not abundant plankton and krill crustaceans to eat.

Consequently, the whales have a slower metabolism

to stay warm as efficiently as possible.

Bowheads are an endangered species and there are currently about 8,000 to 12,000 left.

They travel in small pods and calves weigh as much as six tons at birth. Their only foes are man and orca whales.

Alaskan whalers found the harpoon fragment as they carved the 50-foot long whale up with a chainsaw after using a powerful 21st century gun to kill it.

While commercial whaling is now banned by international agreement, natives from Alaska, the Chukotka region of eastern Russia and Greenland are permitted to hunt a fixed number of whales for traditional, non-commercial consumption.

In Alaska, meat from hunted whales is distributed

to all residents of the hunters' villages.

Biologists can estimate the age of bowhead whales

by studying the changes in levels of aspartic acid, an amino acid found in the eye lens and teeth.

Using bowhead eyeballs, each the size of a snooker ball, they say they can tell the whale's age by the amount of acid, which increases in quantity with the years.