Are Mule Deer Going Extinct?

Writers and speakers often quote Professor Valerius Geist’s opening lines of Chapter 8 in his 1990 book “Mule Deer Country,” where he warned: “For all its current abundance, the mule deer, so different, so uniquely American, so young and promising, is nevertheless a species marked for extinction.”

Geist’s next two sentences, however, are less certain and less quoted: “That may be its fate in the long run. Either the white-tailed deer or man may cause that extinction.”

Three decades later, Geist doesn’t foresee that fate for muleys. “My fears [in 1990] were based on the mule deer’s virtual disappearance from Manitoba and much of the Canadian prairies after white-tailed deer arrived,” he said by email in early August. Geist said subsequent changes in hunting regulations stopped the decline and allow more muley bucks to reach maturity and dominate whitetail bucks during the breeding season. That eased Geist’s fears that whitetail bucks could hybridize muleys into extinction.

Jim Heffelfinger, a researcher at the University of Arizona and wildlife science coordinator for the Arizona Game and Fish Department, said mule deer today are neither doomed nor imperiled. As Samuel Clemens, aka Mark Twain, told a New York Journal reporter in 1897, “The report of my death was an exaggeration.”

Modestly Increasing
So, what is the mule deer’s status? “When someone asks how mule deer are doing and why, you can’t give one-word answers,” Heffelfinger said. “That’s like asking kindergarten teachers how their class is doing. Some kids are up front paying attention, some are napping or daydreaming, and a couple are off in the corner picking their nose.”

Muleys and blacktails—a coastal mule deer—are below population goals set by most wildlife agencies across Western Canada and the United States. Those herds, however, have been mostly stable or slowly increasing the past three years, according to the “2020 Range-Wide Status of Black-Tailed and Mule Deer” report.

This annual report is compiled by the Mule Deer Working Group, 24 biologists representing the states, territories, and provinces comprising the Western Association of Fish and Wildlife Agencies. The 2020 report includes deer herd trends from the group’s states and provinces, of which 12 reported increases, four reported decreases, and six reported stable numbers.

The report also includes state and provincial herd estimates from central Mexico to eastern Alaska, and from the Pacific Coast to the eastern Great Plains. Combined, the West’s mule deer number over 4 million, with blacktails accounting for over 500,000 of the estimate.

Heffelfinger chairs the work group, and notes this caveat in the 2020 report’s introduction: “Several states in the Intermountain West report more recent declines since last year, largely attributed to unfavorable weather conditions.”

Colorado reported the continent’s largest post-hunt 2019 deer herd estimate, 418,000, down from 433,000 in 2018. Colorado’s statewide objective for muleys is 494,000 to 558,000, but the herd has averaged 420,000 the past 10 years.

“When we say deer herds are below objectives, we generally mean agencies aren’t resting on their laurels,” Heffelfinger said. “There’s room for growth, we acknowledge that, and we’re working to maximize their potential.”

The states reporting sizable declines in the 2020 report are Oregon, Utah and Wyoming:

• Oregon — “Mule deer and black-tailed deer are substantially below the long-term statewide management objectives and benchmarks. Following two successive difficult winters (2016-2017, 2017-2018) Oregon’s estimated mule deer population declined precipitously to around 160,000 to 200,000. The black-tailed deer population [declined] to 320,000 in 2004 and seems relatively stable since.”
• Utah — “The current statewide population estimate is 319,150, with a total population objective of 453,100. This is a decrease of over 50,000 deer from previous years, largely due to severe drought followed by harsh winter conditions.”
• Wyoming — “Mule deer populations have declined since the early 1990s and by an estimated 202,000 (42%) since 2000. After the 2019 hunting season, it was estimated there were 343,300 mule deer in the state. This is 28% below the statewide objective of 476,600 mule deer. Nine herds were at objective (24%), 28 herds were below objective (76%) and no herds were above objective. Mule deer populations … trended upward from 2013 to 2016 but decreased the last three years.”

Constant Change
Even though the continent’s mule deer population is up or stable, biologists expect muleys and blacktails to keep increasing or decreasing with changes in habitat, disease, predators, harvest guidelines, and environmental conditions.

Further, given the species’ vast geographical range, factors like moisture vary by year, season, and region. Relatively wet years in Southwestern states generate more fawns and bigger antlers, while drought years cause malnutrition, poor health, smaller antlers, and higher death rates.

Meanwhile, if cold, snowy conditions grip the Northern Rockies, young deer typically suffer the worst of it. As researcher James Unsworth documented in a 1999 study of mule deer survival rates in Idaho, Colorado, and Montana, year-to-year changes in fawns reaching age 1 greatly affect the herd’s annual growth rate. The same conditions, however, had little effect on adult doe survival. The annual variations in environmental conditions are typical of the region and the primary force in winter fawn survival.

On the other extreme, fires often wipe out native vegetation in some arid Southwestern regions, leaving habitats vulnerable to invasive plants that deer ignore. Such fires can burn so hot they scorch soils, destroy minerals, and generate little regrowth.

In mountainous regions, however, fire can spur lush abundance of forbs, shrubs, and young trees. In 2003 for example, muleys benefited from the “Bulldog Fire,” which burned over 30,000 acres of summer range in the Henry Mountains of southeastern Utah. According to research shared by WAFWA, fawn numbers jumped from a five-year average of 44 fawns per 100 does before the fire, to 80 fawns per 100 does after because the flames spurred high-quality browse. Researchers also documented increased body fat and larger antlers for bucks.

To help hunters explore the many factors affecting muleys, the Mule Deer Working Group offers over 30, two-page “Fact Sheets” on everything from predators to hybridization.

Historical Impacts
Even though it’s rare for conditions to align across mule deer country to send the entire population up or down, it can happen. In fact, the second half of the 1900s experienced good and bad “perfect storms.”

Mule deer numbers peaked in many regions during the late 1940s through early 1960s, an era some consider the gold standard for hunting. That peak, however, was likely a one-time occurrence. It began as mule deer rebounded from near annihilation in the late 1800s, when excesses in livestock grazing, subsistence and market hunting, and prolonged harsh weather threatened the deer’s existence.

Deer herds then started booming in the 1920s and ’30s as forage and browse flourished while hunting was reined in and predators aggressively crushed. Mule deer, much like whitetails, benefit from disturbed habitats, and they prospered from widespread logging of vast forests and wildfire suppression and cattle grazing in grasslands. By the late 1940s, deer herds hit record highs for the modern era.

“The huge herds we had in the 1950s and early ’60s simply weren’t sustainable,” Heffelfinger said.

By the late 1960s, habitat conditions were declining for various reasons, including overbrowsing, reduced logging, slowly aging forests, and aggressive fire suppression. Meanwhile, harsh weather in northern regions and widespread droughts in desert regions reduced fawn survival.

Deer numbers kept declining during the 1970s, with herds further reduced by disease, predation, poaching, deteriorating habitats, and competition with elk and whitetails. Many mule deer herds rebounded during the 1980s, but simultaneous droughts in arid regions and harsh winters in mountainous regions late that decade triggered the muley’s third widespread decline in modern history during the 1990s.

That plunge made Geist’s 1990 warning in “Mule Deer Country” sound prophetic.

“It’s clear now that mule deer got hit by a ‘perfect storm’ during the 1990s in most states and provinces, with declining deer populations nearly everywhere,” Heffelfinger said. “Everyone at the time assumed the decline had a single cause, because it affected the mule deer’s entire range. That assumption was wrong, but it also wasn’t caused by white-tailed bucks crossbreeding mule deer does and begetting sterile bucks. Hybrids are rare, and rarities don’t trigger population declines.”

Spurring Action
Nonetheless, “the experts” had no ready explanation for the universal decline as the new century neared. “Sportsmen started chewing on state agency directors, and that got the directors chewing on staff, wondering what was going on,” Heffelfinger said. “The directors started demanding answers.”

That collective chewing and fact-hunting inspired agency directors in 1998 to create the Mule Deer Working Group to study the decline and offer remedies. “As we worked on it, produced documents, and looked at the available research with five to 10 years of hindsight, we realized each regional decline was random and independent, but overlapping and closely synchronized,” Heffelfinger said.

Therefore, biologists could rightfully reply “Yes!” whenever people at public meetings shouted explanations such as harsher winters, drier summers, less logging, more fires, more highways, more development, more elk, more whitetails, more predators, more livestock, more fencing, more gas-oil-mineral mining, more water diversions, more human disturbances, and more new-fangled forestry practices.

The 24 experts in the Mule Deer Working Group have met twice annually since the group’s creation to address those ever-changing challenges. They also compile annual reports that summarize the mule deer’s status in each state and province so it’s easier to track trends, respond consistently, and share information more broadly.

“We don’t have all the deer that hunters want, but it’s inaccurate to say mule deer are in trouble,” Heffelfinger said. “Most agencies want more deer, too. We’ve seen improvements recently, but I doubt we’ll ever again see herds and habitats like those in the ‘good ol’ days’ of the 1950s and ‘60s. Today’s habitats can’t support the numbers we had then, and it would be unrealistic to make that our objective. We’d end up with greater declines if we tried managing mule deer beyond the land’s carrying capacities.”

Likewise, no research suggests predator control will trigger noticeable increases in mule deer. In most cases, predator controls are too expensive and inefficient, and too small in range to benefit entire herds.

As a Mule Deer Working Group fact sheet states, good habitat provides better returns. Healthy deer habitats ensure higher survival rates through better escape cover, better nutrition, better health and less susceptibility to predation.

Conclusion
Heffelfinger and Miles Moretti, president and CEO of the Mule Deer Foundation, urge hunters to support habitat projects in their states. The MDF’s website has links to local chapters and tips for participating in conservation initiatives.

Meanwhile, the Mule Deer Working Group sees room for growth across most of the mule deer’s range. Its experts, however, aren’t expecting another “perfect storm” to do what occurred during the 1990s.

“Each jurisdiction has unique challenges,” Heffelfinger said. “Wyoming’s 42% decline in deer since 2000 is the worst there is. It got hit by repeated harsh winters, followed by droughts. But then you talk to British Columbia’s biologists, and they tell us to quit saying they’re in decline. And then you talk to biologists from Kansas to North Dakota, and they say the eastern parts of their states are running out of mule deer at the fringe of their range.

“I doubt all the states, provinces, and territories will ever be at objective at the same time,” Heffelfinger continued. “It’s more realistic to expect all those jurisdictions to constantly fluctuate. That means we could see mostly ‘stable and declining’ reports five years from now. On the bright side, no one is forecasting extinctions, either.”

Feature image via John Hafner.