Yellowknife (Sep 22/06) - Counting thousands of caribou whose range spans from northern Saskatchewan to the Kitikmeot region of Nunavut isn't easy.

John Nagy, senior wildlife researcher, and Bruno Croft, caribou monitoring specialist, both from the Department of Environment and Natural Resources (ENR) are the duo charged with this difficult task.

Nagy, who is responsible for tallying caribou in the Bluenose East, Bluenose West and Cape Bathurst herds, said a combination of radio and satellite collaring, 10 years of satellite tracking and genetic data makes him, "pretty confident in the location of calving grounds."

And it's at these calving grounds where high resolution photography is employed to capture congregating caribou and the process of counting each one begins.

Between March 18 and April 1, 2006, 59 females and 47 males were collared. In July photo surveys were done of the three herds.

"We try and do the photography in the shortest period of time to minimize mixing of the animals and double counting," said Nagy.

Once photographed and counted, the total number of non-calf caribou are divided by the percentage of collared animals for the final results, which Nagy said are accurate to plus or minus five per cent.

The cost of Nagy's survey - not including ENR staff time - was $650,000.

A majority of the cost went towards the 650 hours of flying time, on both fixed wing aircraft and helicopters, necessary for collaring 106 caribou, and surveying 245,000 square kilometres.

Counting the Bathurst caribou herd rests with Croft and because the herd is much larger than the others and the animals don't congregate so closely together, a different method is necessary.

Only breeding females are satellite collared."We know breeding females come together," said Croft.

Once the percentage of known calving females is approximately 50, an aerial census begins and Croft said 53 per cent of the calving grounds are photographed.

Based on the film, researchers determine the average number of animals and estimate the herd population dispersed throughout the entire calving region.

The department has been monitoring the Bathurst herd since 1986 and previously it was counted every six to seven years.

However, with the drastic decline that was documented in the 2003 count, caribou management policy dictates the time between surveys be reduced to three years.

In the past 20 years, the Bathurst herd population has plummeted from 472,000 to 128,000.