LANDER - Extended periods of cold weather and relatively heavy snowfall could cause more western Wyoming mule deer to die this winter compared to recent years, wildlife biologists said Monday.

While steady precipitation so far this winter bodes well for this drought-stricken region, scientists say deer will probably struggle to survive more than they have during recent, milder winters.

Because of increased precipitation - and long-term weather forecasts anticipating more of the same - the National Weather Service's Climate Prediction Center is anticipating improvement of drought conditions in most of western Wyoming over the next four months, according to the National Oceanic and Atmospheric Administration.

Above-average snowfall this winter in much of western Wyoming is an encouraging development for an area that's been water-parched for five years, said Kent Schmidlin, the regional wildlife supervisor with the Wyoming Game and Fish Department here.

Greater snowpack should improve wildlife habitat in 2008 and help recharge springs, drainages and water tables, he said. But the deeper the snow gets, the harder it becomes for deer to find sufficient amounts of uncovered sagebrush and bitterbrush - the highly nutritious, bushy types of vegetation essential to the mule deer's diet.

In the eastern part of the state - where winter ranges see more consistently high winds - ridges and great swaths of land get blown free of snow, uncovering the vegetation, and generally making it easier for deer there to find food, Schmidlin said.

In the west, however, the snow can pile up and stay put more, over a greater percentage of the deer's winter ranges.

"It's a Catch 22. You need the snow, but you hate to see what some of the results are, too," Schmidlin said. "We need the moisture, but the cold is hard on mule deer, and we'd like to see that moderate some."

As temperatures dip below zero and highs stay in the single digits, it takes more energy for deer to maintain basic body warmth, he said, which means they burn more calories throughout the day and night.

When the snow deepens, more vegetation gets covered up, and the deer have to dig for it or move to wider ranges, Schmidlin said. Both require more energy.

Any additional stress - from predators or domestic dogs, for example - could make it difficult for the skinnier members of the herd to survive the winter.

"They're relying a lot now on body fat that they did put on their frames last summer and fall," Schmidlin said. "It's pretty early in the season, and we've experienced some animal losses already in this part of the state. And we're seeing some underdeveloped fawns in town."

Dealing with drought

Before the winter even started, five years of drought helped stack the deck against western Wyoming mule deer, said Game and Fish biologist Ron Lockwood.

The extended drought could take a significant toll this year on the Wyoming Range herd - the state's largest - which winters around Pinedale, Big Piney, Kemmerer and Cokeville.

"The cumulative effect of five years of drought has definitely decreased forage production in mixed mountain shrub habitats, and therefore deer are going into winter in poorer condition," Lockwood said. "The snow depth and the cold temperatures are going to increase mortality, especially in fawns."

But the rates of mortality will be determined, ultimately, by how harsh the remainder of the winter is, he said. Before the wintry weather arrived, the deer looked to be in pretty good condition, considering they have been dealing with the drought.

Gavin Lovell, a biologist with the Bureau of Land Management, said the BLM, in cooperation with Game and Fish and other agencies, has been working on improving the habitats where the Wyoming Range herd roams, and they're starting to see improvements there. But those improvements aren't going to help deer this winter, as long as the foliage stays buried.

"You can make all the habitat in the world, but once the snow gets deep enough, the wildlife can't get to it," Lovell said.

Mild winters

Wyoming's mule deer population has been increasing for the last couple of years, Schmidlin said, mainly because the animals have endured relatively mild winters.

That trend could change this year.

The Game and Fish regional office in Lander is getting reports of fawns that are too small, that look ill or are underweight as a result of diarrhea, Schmidlin said. Fawns in that condition will have a hard time surviving a harsh winter.

Many of the deer in cities and towns supplement their diets with foliage found around houses and buildings, such as bluegrass and lilacs, especially when other food sources are scarce. This type of vegetation is not as nutritious as the native sagebrush and bitterbrush are for the deer, and might be the cause of, or at least contribute to, the digestive problems in fawns.

Mule deer evolved as browsers, which means they rely predominantly on bushy material for sustenance. Elk, on the other hand, are grazers, and eat more grass.

But elk are also more adaptable than deer, and can switch between different types of vegetation more successfully. Because of this - and because elk are generally hardier animals - Schmidlin doesn't expect them to struggle as much as deer could this winter.

In the short run, Game and Fish expects some losses to the deer population in the west, but if the cold weather moderates, the rest of the winter could be easier on the herds.

* After what was forecast to be the coldest night of the year Monday, the National Weather Service is predicting temperatures will rise out of the single digits and continue higher for the rest of the week across Wyoming

* "We're not going to confuse if for spring or anything, but it should warm back up into the teens and 20s by Thursday or Friday," said meteorologist Dan Berc of the agency's Riverton office.

* Low temperatures this morning were expected to approach minus 20 in the western valleys and below zero in all of Wyoming.

* For a complete weather forecast, please see page B6.]]->