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Last Updated: Thursday, 12 April 2007, 17:45 GMT 18:45 UK
Tags to reveal walrus migration
By Rebecca Morelle
Science reporter, BBC News, Greenland

Walruses (Image: BBC)
Scientists want to find out where walruses are migrating

Scientists are closer to solving the mystery of where walruses head to in the summer months after attaching satellite tags to eight of the beasts.

Until now, the Arctic animals' migration route and destination have remained a mystery to researchers.

A Danish-Greenlandic team had to spend five days off the west Greenland coast in harsh conditions to tag the mammals.

They also hope the devices will shed light on how hunting, oil exploration and climate change affect walruses.

The tags were deployed over a period of two days by the expedition's field leader Mikkel Villum Jensen.

Map of Greenland and Canada (BBC)
Eight walruses tagged
Location data fed to Denmark
BBC News to map positions

"I think it went well and I'm very happy with eight tags," he told the BBC News website.

"We lost two to the big blue shelf, which was a pity - if you have 10 tags in your pocket, you are aiming to get 10 in, but, in general, I'm happy."

The Atlantic walruses of west Greenland are one of at least eight separate sub-populations of the animals.

The creatures were scoped out from a 70-tonne trawler as it ploughed through the ice-covered waters of the Davis Strait, which lies between the west coast of Greenland and Baffin Island, Canada.

'A lot of ice'

The conditions were a lot tougher than the team expected.

Mr Villum Jensen said: "It took five days to finally get to them - there was a lot of ice making it difficult for us to navigate to their habitat.

Tagging walruses in Greenland

"The icy conditions also made it difficult to stealth-in on the animals using the boat, and it was very cold and extremely windy at times, too."

The walruses were eventually located in an area called the Hellefiske Bank, where the creatures dive for clams and other molluscs about 70m (230ft) down. Many of the tusked animals could be seen resting on the ice, often in groups of two or three.

Two different types of tags - one about the size of an ice hockey puck, the other about the size of a cigarette lighter - were used on the walruses.

They were deployed from a few metres away using a crossbow, a carbon dioxide (CO2)-powered gun, and a harpoon that had been crafted by the boat's skipper.

"Most of the animals we tagged were between six and 10 years of age, but we tagged a couple that were 20 years-plus. We tagged an even amount of males and females," Mr Villum Jensen explained.

Walrus watch

The tags will now begin relaying the walruses' co-ordinates via the Argos satellite system. The BBC News website will be following the creatures' movements on its "Walrus Watch" map.

"Previously these tags have lasted between two and three months," said Mr Villum Jensen.

"But I have modified the anchor, so they could hopefully stay on for longer than that."

Satellite tag (left) and a cigarette lighter (Image: BBC)
The team is hopeful the tags will last longer than three months

Erik Born, from the Greenland Institute of Natural Resources, and Rune Dietz, from the Danish National Environmental Research Institute (Neri), will study the data to find out more about the animals' movements. The Technical University of Denmark is also a collaborator on the project.

Mr Villum Jensen said: "The tags will tell us about the walruses' migration; we are not certain where this sub-population in west Greenland spends the summer.

"And they will tell us about their haul-out patterns, meaning how long they spend on ice or land compared to their time in water."

The scientists will also use the tags to find out whether oil exploration is altering the creatures' movements, and they will also help to establish whether the number of walruses being hunted in west Greenland at present is sustainable.

In the longer term, the tagging information could also help to assess how climate change is affecting these Arctic animals.

Mr Villum Jensen observed: "Tags are a godsend to marine mammal research - there is no other way you can find out about where these animals are going."

Walrus distribution (BBC)
It is not clear whether the Laptev walrus is a separate subspecies

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