Low Carcass Count
reflects High Survival

Game Range Ramblin's



Game Range Articles
by Mike Thompson,
FW&P wildlife biologist,
writing for the Pathfinder

 


May 3, 2001
Seeley Swan Pathfinder
Seeley Lake, Montana


by Mike Thompson

 

On the African plains, the struggle for life plays out most fiercely around waterholes in the dry season. Predators and prey are confined to small spaces by extreme environmental conditions, and the competition for grass, meat and time is severe.

In northern latitudes, this script is played out in a much different, but equally severe environment every winter.

And, when predators and prey all come together every December-April on the Blackfoot-Clearwater Game Range, it's a date with destiny for many elk, mule deer, white-tailed deer, porcupines, coyotes, lions and others, set against a backdrop of seemingly limitless environmental variables and stresses.

Wind, cold and snow. Is it a chinook or blowing stiff out of the north? Will it last for a few hours or a few days? Has it come late in the fall or early in spring? Is it on the heels of a cold snap, or have temperatures been mild? Is the snow deep or patchy? Is it fluffy or crusted?

It all makes a difference.

But, before your mind conjures up images of death and destruction on a massive scale, consider the results of FWP's annual carcass count on the Game Range, which was accomplished last weekend.

Once again, this year's survey was directed by its originator, James Jonkel. Jamie is uniquely skilled in the art of reading sign left by wildlife, and is a highly experienced observer of predator-prey interactions. He's also unusually effective in gathering and coordinating teams of volunteers, with at least one experienced leader for each team.

Included among his more experienced volunteers were Tom and Melanie Parker of Northwest Connections, a wildlife research-support and educational establishment based in Condon. Heather Marstall, who I believe has participated in all 5 surveys since they were begun in 1997, won the prize for travelling the farthest, having come from Utah to join the effort.

All told, 58 people (mostly students and neighbors) scoured roughly 20 square miles where most of the 900 elk, 500-700 mule deer, and 400-600 white-tailed deer endured the most trying environmental stresses of the year with a full compliment of predators, including the occasional wolf.

You would think that more than 32 carcasses of deer and elk would have been found.

That is, you might think so if you had never tried this before. This year's count of 32 was up slightly from last year's count of 28, and was higher than the low count of 24 in 1998. We have the hard winter of 1996-97 to compare as a benchmark, when 66 carcasses were found during that first survey.

Only 3 of the carcasses were elk, and the remaining 29 were deer of either species. This was a similar proportion of elk and deer as last year, but was a lower proportion of elk than we saw in earlier years.

This year, carcasses generally were in poor condition for determining the cause of death. In past years, predation-caused deaths comprised roughly half of the sample, with the remainder classified as having died from malnutrition or unknown causes.

It seems that carcass totalsand kills by predatorsrise and fall with winter severity. Jamie's highest total of 66 corresponds with the most severe winter conditions he's sampled. Counts in the twenties correspond with milder winters, and an intermediate count of 39 in 1999 corresponds with a winter we would consider to be "average" in its severity. One would surmise from this that predators have easier pickings when their prey is stressed and concentrated in adverse weather conditions, but are not as effective without this advantage.

This year's count of 32 seems to fall in line with expectations. Sure, we had snow on the ground for a very long time this year. But, this was balanced by the fact that snow depths were shallow and temperatures were reasonably mild. I only recall one blizzard, but its duration was brief and its expected effect on wildlife survival was minimal.

Although two wolves were seen on the Game Range by a neighbor this winter, and these or others were seen occasionally in the vicinity as well, wolves have yet to exert a predatory influence on our wintering elk and deer populations that we can detect by searching for carcasses in early spring. Because the carcass counts seem sensitive enough to reflect perceived annual changes in winter severity, I would also expect them to be sensitive enough to pick up any significant change in predation rates by wolves. Time will tell.

By all indications, local numbers of elk, mule deer and white-tailed deer are increasing in the face of the predatory forces they endure today. The only obvious area of concern is the spring-summer survival rate of elk calves, which has been unusually low in recent years, and has caused the elk population to increase at a slower rate than we are accustomed to. We won't solve that problem today, though.