The Western Arctic Caribou herd is the largest in the world, currently at an estimated 265,000 strong...............Ten years ago, the herd stood at about 430,000 so many wonder if a continued slide in numbers will continue to occur annually.............The interesting thing is that the herd overall seems healthy, with few skinny animals observed, and less parasites and disease noted than has been seen in the past..............Alaska Game and fish biologist Jim Dau tells us that "for many caribou herds, and especially for the largest herds, the difference between population lows and highs can be extreme"........ "When the(Western Arctic herd) last declined it went from about 242,000 caribou in 1970 to roughly 75,000 caribou in 1976 - an average 18 percent decline each year"......... "There was uncertainty associated with the 1976 population estimate but, regardless of the exact number, it is clear that the herd 'crashed' during that time".....................Calf recruitment is up but the survival rates of the youngsters are down,,,,,,,,,,,,,,,,,,,,,,,Environmental factors could be playing a role with warm, dry conditions affecting the quality and quantity of vegetation............... This year's unseasonably warm fall left many south of the North Slope waiting for the herd to move............. Weather conditions also affect the number of mosquitoes which can be incredibly intense on the North Slope

http://www.thearcticsounder.com/article/1350caribou_numbers_continue_to_decline

Caribou numbers continue to decline

December 13th 11:46 am | Jillian Rogers      

The population of caribou in North America's largest herd is continuing to fall.

And those in the know aren't exactly sure why.

There are several possible explanations for the drop in numbers of the Western Arctic Caribou Herd, said Kotzebue biologist Jim Dau last week in Anchorage. But most likely, it's a combination of several factors.

In a presentation at the annual meeting of the Western Arctic Caribou Herd Working Group, Dau, a biologist for Alaska's Department of Fish and Game, updated the group on the herd's movement and herd health over the last year.

The herd, which at last count in 2011 was around 325,000 animals, has been decreasing by about 4 to 6 percent each year since 2003. That year, it reached its peak at 490,000 caribou.

If numbers continue to slide, the total number in the herd could reach as few as 265,000 caribou this year. If that's the case, agencies and stakeholders will have to shift to a more conservation management plan, Dau said.

He added that it's "worrisome" how quickly mortality rates are changing from year to year.

While calf production is up, the calf survival rate is going down, he said. And mortality rates for adults, especially cows, has increased.

Environmental factors could be playing a role with warm, dry conditions affecting the quality and quantity of vegetation. This year's unseasonably warm fall left many south of the North Slope waiting for the herd to move. Weather conditions also affect the number of mosquitoes which can be incredibly intense on the North Slope, Dau said.

The herd overall seems healthy, with few skinny animals observed, and less parasites and disease noted than has been seen in the past. Haptoglobin levels, which indicate inflammation and disease, are scattered across the board. There's no real pattern, Dau noted.

Every year, members of herd die off because of accidents — falling through thin ice, etc. — and while those incidents contribute to the dip in numbers, it's not the cause of overall decline.

"Everyone wants to know what's killing them," Dau said. But there's no easy answer.

Starvation, predators, harvesting and guided hunts could all be contributing factors, but again, there is no clear-cut reason.

Harvest numbers have remained stable with 8,000-12,000 caribou taken by subsistence hunters each year and most of the subsistence hunts happening in Unit 23, the Northwest Arctic.

Currently, there are no restrictions on bulls harvested by resident hunters and that will continue as such unless bull-cow ratios fall below 40 bulls per 100 cows.

Dau added that fluctuations in population are perfectly normal, and an updated count of the herd will be released in 2014.

"For many caribou herds, and especially for the largest herds, the difference between population lows and highs can be extreme," Dau wrote in a report for the working group. "When the (herd) last declined it went from about 242,000 caribou in 1970 to roughly 75,000 caribou in 1976 - an average 18 percent decline each year. There was uncertainty associated with the 1976 population estimate but, regardless of the exact number, it is clear that the herd 'crashed' during that time."

Many herds in Canada having seen numbers fall in the past decade, as well, he added.

"This is not necessarily evidence of bad management or irresponsible use, it has probably been happening for tens of thousands of years."

The impact on the declining caribou population will depend on how low the numbers actually go. Around 200,000 is the lowest number before more direct conservation action should be taken.

No one wants to wait until the herd is in a critical state to take action, said Roy Ashenfelter, the outgoing chair of the group.

The public should be well informed so that there are no surprises.

"We need to use the venues that we have to start getting the message out that things are changing in terms of the population of the herd," he said.