Wildlife management agencies, hunters and wildlife organizations have done a lot of research, habitat work and plain old head scratching in recent years over what is causing a decline in the number of mule deer across parts of the West.
A recent report by Western wildlife agencies found mule deer declining in four states, including Wyoming, and one Canadian province. Montana’s population was reported as stable, although certain regional populations have seen some dramatic declines.
“Certainly numbers are still down,” said Quentin Kujala, Fish, Wildlife and Parks wildlife management section chief, but whether that constitutes a downward trend or simply a temporary pause he could not say.
“It’s varied across the state, for sure,” he added.
A FWP report to the Western Association of Fish and Wildlife Agencies in July noted “significant declines in recruitment and observed numbers of mule deer during 2007-11.”
The report goes on to note the regional differences in mule deer populations.
“Surveys during 2012-13 revealed improved recruitment and stable numbers in central and eastern Montana. Western Montana mule deer populations continue to perform poorly. Recent, significant declines in eastern Montana mule deer populations were associated with inclement winter/spring weather and drought.”
Down in Wyoming
Wyoming, on the other hand, is reporting a steadily decreasing population of mule deer.
In its report to WAFWA, Wyoming noted that the decline was evident as early as the late 1980s, when fawn production began to decline, blamed on “decreasing habitat availability and/or quality.”
The report goes on to note that, “Over the past 30 years, fawn productivity, on average, has decreased statewide by about 20 percent and has been below 65 (fawns per 100 does) 12 times.”
That number is significant since any time the numbers hit 65 or lower there will be a decline in populations, said Darryl Lutz, Lander Region wildlife coordinator for the Wyoming Game and Fish Department. That’s been the case in the Cowboy State.
“Throughout Wyoming, mule deer populations have declined by an estimated 168,000 (31 percent) since 2000. After the 2011 hunting seasons, it was estimated there were 376,000 mule deer in the state. This is 24 percent below the statewide objective of 564,650 mule deer,” Wyoming’s WAFWA report stated.
Lutz said that in 1989 Wyoming saw fawn production start to drop off significantly. That corresponded with the beginning of an extended drought.
Other states that reported declines include North Dakota, Colorado, New Mexico and the province of Saskatchewan. In Colorado the decline of mule deer was great enough that the deer hunting opportunities dropped by 94 percent over five years for the state’s largest mule deer herd.
Mule deer habitat
One theory behind the animals’ decline is a loss of habitat, or changes to existing habitat.
Mule deer are ruminants, animals with multi-chambered stomachs that help them break down the often fibrous plants they eat, which includes the tips of shrubs like bitterbrush and sagebrush.
The mule deer’s range across the West, as in Montana, varies from high in the Rocky Mountains to rugged prairies like the Missouri River Breaks. One thing all of the various mule deer habitats have in common is their reliance on timely moisture to produce nutritious forage. So drought – which commonly and sometimes seriously strikes the West – can deplete mule deer populations.
Demonstrating the importance of quality nutrition, one study found that “well-nourished does lost only about 5 percent of their fawns; does fed deficient diets during the winter lost about 33 percent; and does underfed throughout their pregnancy lost 90 percent of their fawns.”
Lutz, from Wyoming Game and Fish, said his agency once believed that winter habitat was the most important factor in ensuring the deer’s survival. In recent years, that switched to a greater focus on the habitat deer use in the late summer and fall. “This is a common theme across areas of the West,” Lutz said.
If deer aren’t going into the winter well fed, it doesn’t matter if the winter range is in good shape or not. Deer in poor condition won’t survive, or a pregnant doe’s fawn has less chance of surviving.
Altering habitat on a large enough scale to affect mule deer populations isn’t easy or cheap, though, Lutz pointed out.
“It takes a lot of money to do it on a scale large enough to make a difference,” he said.
Still, the department is partnering on a project near Saratoga, Wyo., called the Platte Valley Habitat Partnership, to see if large-scale landscape improvements can have a positive effect on mule deer population trends.
“We’re refocusing our attention,” Lutz said. “I don’t think we yet understand how much effect drought has on habitat.”
Although drought may be a major player in the decline of mule deer, there is a laundry list of other occurrences affecting mule deer habitats, including weed infestations by nonnatives, especially species like cheatgrass that can spread rapidly following fires. Fire, too, has the ability to reshape habitats – sometimes for the good, by removing old overstory and promoting new growth, and sometimes for the bad, by ridding the landscape of cover vital to fawn survival.
Some studies suggest that the increase in logging during America’s building boom, settlement of the West and the mining boom, may have opened up the forest floor to species more palatable to mule deer in the early 1900s, promoting what some have termed the golden era of mule deer.
Longtime Wyoming hunter Mike Eastman, who has written two books on mule deer, said the lack of hunting during World War II also helped mule deer populations blossom in that era. He puts part of the blame for the population decline on liberal hunting seasons following World War II.
“They treated them like buffalo and killed them all off,” Eastman said. “By the 1970s, they were all gone and they went, ‘Oops.’ They’ll never be like that again.”
Eastman blames the lack of predator control, suppression of fire and the encroachment of development on deer habitat as the top three reasons for the declining mule deer populations.
One curiosity is that mule deer have thrived in some urban environments, such as in the Montana towns of Colstrip, Glendive and Helena, prompting special hunts or outright trapping and removal. Are mule deer numbers in towns swelling because of the well-watered forage provided by homeowners, or maybe because of a lack of traditional predators like coyotes, or both?
Other possible suspects in the decline of mule deer are competitors for the same resources — animals like elk, whose numbers have climbed in many regions of Montana, as well as cattle.
There is often a big decline from the number of fawns born to those living at a year old, and predators such as coyotes, bears and lions are often blamed for limiting mule deer population rebounds. Utah has even gone so far as to pay a $50 bounty for coyote pelts as a way to reduce their numbers.
But studies have shown that reducing the numbers of predators isn’t always effective. One study suggested that if mule deer numbers are strong, then predators will simply fill the void if a resident predator is shot, since the food source is so bountiful, creating a constant in-migration.
A Montana study showed that coyotes, if they have other food sources such as small mammals, may not be a problem even when abundant. And research in Nevada showed that even when predator control was at a high in the 1960s, game harvest was better in 1996 and 2000 when many of the old means of killing coyotes, such as with poisons, were no longer used.
Despite many studies, it seems there is still a lot of uncertainty about how to reverse the decline of a species that many consider a Western icon. The only thing that is certain is that there are no easy answers.
“It’s complex,” said Lutz, of Wyoming Game and Fish. “The things that are impacting mule deer are numerous.”