BIG BOUNDARY LAKE For the fourth and final time, 45 caribou calves and their mothers left a pen along the banks of Big Boundary Lake and headed toward the alpine to join the rest of the Chisana herd.

With the rearing aspect of the Chisana caribou project having now concluded, Kluane regional biologist Michelle Oakley said Wednesday it is time to focus on learning what the root causes are for the herd's decline.

'It's time to take a break and look at what's really going on here,' said Oakley.

The Chisana project began in 2003 after concerns were raised about the trans-boundary herd's decline during the 1980s and 1990s.

The herd, which once numbered around 1,800, was shrinking at a rate of approximately six per cent per year prior to the start of the project.

The herd, now approximately 700 strong, has had its decline slowed to about two per cent annually since the start of the project.

The $300,000-a- year effort saw the net capture of pregnant cows each year and their transport to a Klutlan Plateau pen in the southwest corner of the Yukon, where they would be kept until at least a week after the birth of the last calf of the group.

The theory was to give the mothers and their babies extra protection for the first weeks of the calves' lives until they grew big and strong enough to better outrun their predators.

There have been 136 calves released since the start of the project.

This year's calves were born in mid-May, placing them all at about a month old upon Wednesday's release.

All 50 of the captured cows gave birth. However, two were stillborn, one's cause of death is unknown, and one was caught by a black bear that managed to get into the pen last Saturday.

The team on-site hasn't been able to determine how the bear got into the pen there were no breaks in the fencing. When it was spotted inside, it was shot, and samples have been sent for testing in British Columbia.

A calf sent to the Yukon Wildlife Preserve north of Whitehorse last week has also been euthanized.

Its mother had died only days after giving birth due to a twisted uterus that caused internal bleeding and an infection.

It is believed the calf, which suckled from its mother, may have ingested some of the infection's toxins. The animal was having trouble suckling from a bottle at the preserve and also was showing signs of neurological problems before it was decided to put it down.

The survival rate of the released calves over the years has been about 70 to 75 per cent reaching five months old, said Jamie McLelland, a wildlife technician with the Department of Environment.

Of those, about 80 per cent reach their first reproduction at about two to three years old, said Oakley.

The numbers are significantly higher than the caribou born in the wild, where the survival rate is about 15 per cent.

'The research after the pen is just as intense,' said McLelland.

The project has really been approached as the problem with the herd as being neonatal, or the death of the calves, said Oakley. But she suspects there may be other underlying issues.

'My hunch is that it's not a predation problem,' she said. 'I think other things are setting them up for predation.'

Now the project will be looking at the Chisana's range to see if the area they travel on has more to do with their dropping numbers than predators attacking the young.

A volcano erupted in the region about 1,200 years ago. It has left the landscape covered in volcanic ash that may be having an effect on the vegetation, parasite survival and how the caribou grind their teeth, she said.

Some of the herd has demonstrated potential signs of an iodine deficiency, she added, and it may be found there is a disease in the herd that has been wreaking havoc on its numbers.

The average age of the members of the herd is about 10 or 12 years old, said McLelland. For a caribou to reach 14 or 15 years is 'really old,' he said. 'That's what puts this herd in a crisis.'

Previously, with almost no calf survival there were only older caribou left, who have a far lower reproduction rate.

Over the coming years, as the more senior herd segment dies off, it is hoped the project will have helped the younger ones move forward, he said.

Currently about 30 to 40 per cent of the herd is made up of animals released by the project, said Oakley.

Nutrition is also being examined, because of the higher survival rate of the captive-born calves, who are usually eating the veterinary-designed reindeer pellets before they leave the pen, said McLelland. The pen calves also generally appear stronger and to have put on more weight than other animals their age.

Oakley said she expects there to be a lot of information about the herd after another three years of research outside of the rearing project.

Laboratory tests and scientific research will now be kicking into high gear, she said.

The continued study should lead to the determination of the root cause of the decline, she said. Especially, if it is something that wildlife management can even do anything about, said Oakley.

If it's an iodine problem, the solution could be placing salt-licks around the range; if it's a predator problem, a control program could be explored, she said.

But it might be found it is something completely beyond wildlife management's control, such as a disease or a natural fluctuation, she added.

'Herds do fluctuate and go extinct naturally,' she said.

Those factors should be determined before more money is spent on the rearing, she said.

White River First Nation Chief David Johnny disagreed and intends to express that at an upcoming meeting to discuss the future of the project.

Johnny said he believes the rearing program should continue for at least another three years.

'Right now we're just at a teeter-totter point. We'll either go for the bad or go for the good,' Johnny said. 'If we stop now, the caribou may just plunge down.'

Johnny added he also suspects there may be a disease found to be in the herd. But he believes human impacts on the ecosystem may be a contributing factor.

So many jets fly over the herd's range and drop pollutants onto the caribous' grazing areas, he said.

'There's something in the system that we need to find out. We're just on the verge of finding out now.'

Johnny said it was a great feeling to watch the cows and their calves hesitate for a moment before leaving the pen and then running as a pack up a hill only to disappear over its summit on their journey to rejoin the herd.

'It's a new way of putting animals back on Earth, instead of always taking. We need to help some of these animals get back on their feet,' he said. 'It makes you feel really good that you're part of it.'

A lot of people feel the caribou are an important part of the landscape, and if they don't survive, it could have other implications for the range's bio-diversity, said Oakley.

'It speaks to the heart of this project, all the different people that have been involved,' said Oakley. 'It's definitely not the end of the effort.'