Monitoring Muleys

Monitoring Muleys

How FWP figures out mule deer population trends and harvest recommendations, and why biologists say now is the time to issue more B licenses in southeastern Montana. By Tom Dickson.

This story is featured in Montana Outdoors September–October 2016 issue

It was five long years ago, but Dean Waltee vividly recalls what the winter of 2010-11 did to mule deer in southeastern Montana. “The record cold and snow we saw that year decimated mule deer populations in our region and throughout eastern Montana,” says Waltee, at the time the Montana Fish, Wildlife & Parks biologist in Broadus. FWP Region 7’s mule deer population, the state’s largest, bottomed out in 2012 but has since rebounded to where it had been and beyond. Biologists attribute the increase to three consecutive mild winters, the replacement of older deer that died with younger, more productive deer, and a cutback by FWP in antlerless mule deer harvest. By spring of 2016, biologists estimated the population had grown to 47 percent above the long-term average. “We haven’t seen numbers like this since the late 1990s,” says John Ensign, FWP Region 7 wildlife manager.

Because of the rapid increase, FWP wildlife biologists say now is the time to start moderating the population growth by issuing more B licenses, or tags, which allow hunters to harvest additional antlerless deer. That will prevent muleys from overpopulating and eating themselves out of house and home.

Boosting antlerless harvest this fall is a smart move, say FWP officials. But to many hunters, issuing more B tags seems illogical. If deer numbers are increasing, they ask, why not let the population continue growing and then hold it at a high level year after year?

Creating confidence
“We haven’t always done the best job of explaining to the public how mule deer management works,” says Waltee. “Basically, what we do is survey mule deer populations and estimate mule deer harvest, and then use that information to decide on appropriate harvest levels for the upcoming fall hunting season.”

Twice each year biologists count, from airplanes, the number of deer in large survey areas across Montana’s mule deer range. “We can’t go out and count every deer. That’s literally impossible,” says John Vore, chief of FWP’s Game Management Bureau. “What we and many other states do is count deer in areas representative of the region’s habitat, private and public land ownership, and public hunting access. That and other information tell us whether the overall mule deer population trend from year to year is increasing, decreasing, or staying stable.”

Mule deer aerial surveys montana

Biologists fly over the state’s 101 survey areas between December 1 and January 15 to determine the proportion of bucks, does, and fawns. They fly the same areas again from March 15 through April 30, when deer are concentrated in open areas during spring “green-up,” to see how well fawns and adults survived the winter.

Hunters who don’t see as many deer as biologists report may wonder if the surveys are focusing too much on private property, where deer numbers might be higher than on public land. Vore says that’s not the case. In the state’s main mule deer regions of central and eastern Montana, 41 percent of the survey areas are on public land or private Block Management Area property. “That’s a higher percentage of land open to free public hunting than exists in the regions as a whole. So we are surveying representative areas accessible to all hunters,” Vore says.

Still, isn’t it possible that deer move far from the survey areas by the time the fall hunting season rolls around—which might account for why some hunters don’t see as many deer as FWP says are out there? “We looked into that,” says Justin Gude, chief of FWP’s Wildlife Research and Technical Services Bureau. Biologists tracking radio-collared deer found that one-third stay in survey areas during the fall, while the other two-thirds move away from the wintering areas only three miles on average. “Where we see the deer in the winter is pretty much where they will be next fall,” says Gude.

Another way FWP takes the pulse of mule deer populations is by monitoring hunter harvest at check stations and with winter phone surveys. “That harvest information almost always tracks with what we saw in the aerial surveys,” says Gude. “If our winter and early spring surveys show an upward trend in deer numbers, we usually see more hunters with deer in the back of their pickups the following fall.”

Another way biologists assess deer numbers is by regularly talking with landowners about wildlife populations they see on their property and by monitoring and addressing game damage complaints. What’s more, over the past several years FWP has radio-collared and tracked 1,134 mule deer to see how well the animals survive and where they go. “All that information, added to the harvest data and aerial surveys, gives us confidence that we know what’s going on with the mule deer population,” says Vore.

The overbrowsing effect
Even though FWP biologists know that mule deer populations in southeastern Montana are rebounding, how can they know for sure when to start increasing antlerless harvest to scale back that recovery? A 34-year-long experiment in the region provides answers.

Muley populations rise and fall naturally based largely on how weather and habitat conditions affect deer survival and reproduction. A major factor is the amount of forage (forbs, or wildflowers) and browse (shrubs) available to deer each year. When summer vegetation is lush, deer put on a thick layer of body fat to help them through the following winter. When plant growth is sparse, a hard winter can cause large numbers of malnourished deer to perish or, in the case of does, reabsorb developing fetuses.

Deer population extremes are a problem. When overabundant, mule deer overbrowse shrubs such as mountain mahogany and bitterbrush, which can take years to recover. “Because continual overbrowsing reduces the amount of browse through time, it slowly reduces the number of deer the habitat can sustain,” says Waltee, now the FWP biologist in Sheridan. “That’s what we’re seeing in southwestern Montana.”

Hungry deer also cause problems for landowners by raiding hay bales and grazing pasture. “Population extremes are always a problem for someone,” says Waltee. “Too many deer, and landowners get mad. Not enough deer, and hunters get mad.”

Wildlife biologists can use hunting regulations to moderate deer population extremes, but only if timed correctly. “Before 1982, our mule deer hunting regulations here in Region 7 were ‘reactive,’ meaning we would wait too long to increase antlerless harvest when populations were increasing,” says Melissa Foster, FWP wildlife biologist in Baker. Foster explains that when a deer population increases naturally due to several years of abundant vegetation, it eventually exceeds the land’s “carrying capacity,” or ability to support that many deer. “It might seem that having a lot of deer is great for hunters, but in the long run it’s not,” she says. With less browse available, undernourished does produce fewer fawns, leading to depressed populations over the long term. “The land can’t sustain a super high deer population for extended periods,” she says.

The most striking example of this boom-bust effect came in the early 1970s. Mule deer numbers in Region 7 were skyrocketing because FWP had restricted antlerless harvest, even during years of abundant browse. In 1973, hunters harvested a record 19,335 mule deer bucks. During the next few years, FWP finally increased antlerless harvest, but by then the population was already dropping naturally, as mule deer found little left on the landscape to browse. Coming too late, the increased antlerless harvest accelerated the population decline. By 1976, the buck harvest had plummeted to just 3,498, a decrease of 82 percent. “That’s a prime example of reactive harvest management,” says Waltee. “In hindsight, we now see that the increased antlerless deer harvest came two years too late to prevent severe habitat stress and an extreme population decline.”

The “adaptive harvest management” approach
Since 1998, FWP has followed an “adaptive harvest management” (AHM) approach for mule deer in Montana. Like a similar process long used for waterfowl management, AHM is based on decades of research and experience and allows FWP to accurately detect changes in mule deer populations and respond quickly with appropriate hunting regulations.

FWP’s AHM document—the agency’s mule deer management “bible”—recommends restrictive, standard, or liberal harvests each year based on two main criteria: how the number of fawns per 100 adults each spring compares to the long-term average, and how the springtime deer population compares to the long-term average. Biologists also consider factors such as deer age structure, winter survival, buck-to-doe ratios, habitat conditions, and hunter preference and satisfaction.

“This year our Region 7 mule deer population was well above the long-term average, but fawn production wasn’t quite high enough to trigger the full liberal harvest package,” says John Ensign, FWP regional wildlife manager in Miles City. “To stay as true as possible to the AHM prescriptions while still proactively addressing burgeoning deer populations, we decided to issue 7,500 B licenses this year.”

R7 mule deer management

Ironing out the extremes
Starting in 1982, Region 7 made two major mule deer management adjustments. One was to change from setting seasons and issuing licenses for each of 35 different hunting districts to creating a regionwide season and issuing licenses valid across the region. “It’s like we became one big hunting district,” explains Ensign. Under this approach, biologists, hunters, and landowners working together can quickly increase hunting pressure in areas with high deer densities and decrease it in areas with too few deer. And they can make these adjustments during the deer season, rather than waiting a year to adjust regulations for the following season. “If a landowner has too many deer, we can direct hunters to that property as soon as he calls,” says Ensign. “We didn’t have that kind of flexibility under the old system.”

Region 7’s other big deer management change was to begin issuing more B tags when fawn production and populations started taking off, rather than waiting until numbers reached a peak. “In the past, by the time hunters said, ‘Jeez, you’ve got a lot of deer out here,’ those populations had already stressed the habitat and were starting to decline,” says Ensign. “Using this proactive approach, we increase harvest a few years before populations would otherwise hit their peak. That way vegetation stays healthy, fawn production remains steady, and we reduce those wide population oscillations.”

The proactive approach has ironed out the extreme mule deer population highs and lows across Region 7 (see graph, page 24). “That in turn allows hunters to predict and plan for the coming years, and it also reduces game depredation on farms and ranches,” says Ensign. He notes that landowner complaints in Region 7 have steadily declined over the past three decades to just 20 percent of what they were in the early 1980s (see graph below).

R7 landowner feedback

Vore says that Region 7’s proactive management approach could work in other regions, and for whitetails too. “For instance, many whitetail hunters in Region 1 (northwestern Montana) don’t want us to issue B tags until the population is at its peak,” he says. “But by then it’s too late, and there are too many deer. That leads to the crashes we’ve seen in the past.”

To prevent a collapse in Region 7, FWP is increasing the number of B licenses available this fall, based on an “adaptive harvest management” process the department uses for deer management (see sidebar, page 23). In July, the Montana Fish and Wildlife Commission approved selling 7,500 regionwide B licenses for 2016, up from zero just two years ago. The commission will also allow the region to issue up to 11,000 B licenses in the future if surveys show continued growth in fawn production, fawn recruitment (young deer that survive their first winter), and overall deer numbers. Hunters usually fill about half of those tags, Vore adds.

Hoping that high deer numbers can be sustained, some hunters wonder if FWP is acting rashly. “The belief is that we can ‘protect the herd’ by not harvesting does,” says Waltee. “But invariably a too-high deer population leads to a crash. There’s simply not enough habitat to support high deer populations year after year.”

Such a plummet is likely if Region 7’s burgeoning mule deer population continues rebounding at the current pace. “Having lots of deer is great for hunters in the short term, but already we’re seeing habitat degradation,” says Vore. “Within a year or two, those increasing numbers of deer will be back hammering the habitat again, and we don’t want that.”Bear bullet

Why mule deer are declining elsewhere in Montana

While the mule deer population in southeastern Montana is booming, numbers elsewhere in the state—and throughout the West—remain lower than several decades ago. They will likely stay that way. The population decline stems largely from a decrease in quality habitat available to mule deer in central and western Montana caused mainly by:

  1. The spread of conifers: Douglas fir, Rocky Mountain juniper, and other conifers have spread across mountainsides and foothills. The conifers outcompete the forbs, shrubs (such as mountain mahogany, antelope bitterbrush, and sagebrush), and young quaking aspen that mule deer eat. This “conifer expansion” has been caused by decades of fire suppression and reduced tree cutting on federal, state, and private lands.
  2. Competition from elk and whitetails: Elk and mule deer share much of the same habitat. Though their diets don’t overlap completely, an elk eats three times more than a mule deer and is better able to reach browse in deep snow. In much of Montana’s prime mule deer country, elk numbers are now three or four times greater than they were in the 1980s, and they have taken over areas previously dominated by mule deer. For instance, in several hunting districts in southwestern Montana, winter elk counts have increased from a total of about 4,000 in 1980 to more than 17,000 in 2015. Mule deer numbers in those same hunting districts have declined by 64 percent.

Mule deer also face competition from white-tailed deer, which generally do better in areas altered by human development.

“The increase in conifers, elk, and whitetails in mule deer country is the new normal,” says John Vore, chief of FWP’s Game Management Bureau. “We’ll never have muley numbers in western Montana like we did in the 1980s unless we can magically change all that and make everything like it was 40 years ago.”

Tom Dickson is editor of Montana Outdoors.