Study: Shooting More Rutting Bucks Reduces CWD
Here’s some news the Department of Natural Resources probably won’t share with its seven-citizen policy board, or the folks now reviewing Wisconsin’s 2010-2025 CWD management plan:
A new study based on extensive harvest data from 36 Western U.S. and Canadian mule deer management units found that shooting more bucks in one year consistently reduced chronic wasting disease cases the next year. That strategy proved most effective when the harvests occurred near or during the rut, i.e., the deer’s mating period. That’s probably because rutting bucks take more risks, and mature bucks are more likely to carry CWD, which makes them even more vulnerable to hunters.
In effect, the rut helps hunters remove bucks/CWD cases more efficiently from the landscape.
The researchers from Utah, Colorado, Nebraska, Wyoming and Alberta made those conclusions after reviewing 10 to 19 years of harvest data. The researchers also found that sustaining higher buck harvests for several years reduced CWD prevalence in adult bucks. Those increased harvests were especially effective if they occurred soon after CWD first appeared in an area, and before it reached 5% prevalence in the herd.
The study, titled “The Relationship Between Harvest Management and Chronic Wasting Disease Prevalence Trends in Western Mule Deer,” appears in the Oct. 2021 issue of the Journal of Wildlife Diseases (https://bioone.org/journals/journal-of-wildlife-diseases/volume-57/issue-4/JWD-D-20-00226/----Custom-HTML----THE/10.7589/JWD-D-20-00226.full).
Wisconsin native Jim Heffelfinger is a researcher at the University of Arizona and the wildlife science coordinator for the Arizona Game and Fish Department. Heffelfinger also chairs the Mule Deer Working Group for the Western Association of Fish & Wildlife Agencies. Heffelfinger said this study suggests agencies could slow, stop or reverse CWD’s spread and infection rates by focusing more hunting pressure on bucks during the rut.
As the researchers wrote, “We believe it encouraging that modest increases in harvest might be sufficient to slow epidemic growth or stabilize prevalence in some areas.” The study found that for every 100 additional bucks shot annually in a management unit, CWD prevalence dropped 2%. Likewise, for every 1,000 bucks killed, CWD prevalence fell 19%.
Heffelfinger said states aren’t helpless if CWD prevalence reaches 5%, even though that’s when it starts expanding exponentially. He notes that Colorado added five management options in 2019 to address herds where CWD exceeds 5% in in bucks 2-plus years and older. The options include reducing deer densities, reducing buck-to-doe ratios, reducing the average age of bucks, targeting CWD hotspots with more hunting/shooting, and removing food sources that concentrate deer.
“No one said conservation was easy,” Heffelfinger wrote in a recent Mule Deer Foundation magazine article. And in an Oct. 27 email to fellow Western biologists Heffelfinger wrote:
“Science is science, and sometimes it gives us information we don’t want to hear. We know mature bucks have higher CWD prevalence, and we know disease spreads faster in higher-density populations. If one wanted to increase a deer herd’s CWD percentages, and you wanted to spread it over a larger geographic area, you would manage the herd at the highest densities possible and try to maintain the highest number of mature bucks on the landscape.
“But if you want to limit CWD prevalence in wild deer, you’d want to do the opposite,” Heffelfinger continued. “Management changes aren’t popular, but science isn’t a popularity contest. Faced with these data (from the October 2021 study), agencies in CWD-endemic areas must decide what they’re going to do. Will it be status quo, or identify management units with CWD issues and try some harvest management changes?”
I can’t predict what Western states will do, but Wisconsin lawmakers long ago pressed a shotgun to Status Quo’s back and marched it to CWD’s altar. That’s why a panel now reviewing Wisconsin’s 2010-2025 CWD management plan has this spineless goal:
“Wisconsin DNR will take input on actions to influence CWD that are within the capacity of the agency to implement; and within legal, political, social (i.e., willingness of hunters to harvest deer), and cost constraints.”
Translation: “The DNR will take input that helps it measure, but not hinder, CWD’s spread. Other than update deer-baiting bans, DNR leaders won’t try to slow, stop or reverse CWD’s spread and infection rates.”
Talk about selective leadership. Recent events show the DNR will defy lawmakers and the Natural Resources Board’s disease-spreading majority on wolf management, but it won’t show equally principled, science-based leadership for white-tailed deer.
If you think that’s harsh, ask yourself how deer management changes when the DNR detects CWD in new areas. The answer: Nothing changes, unless you’re a bait-master.
On Oct. 29, for example, the DNR reported the first case of a wild deer with CWD in Fond du Lac County. The DNR simply reminded everyone that deer baiting will now remain illegal at least three more years in that county. Our ever-friendly DNR also “encourages” Fond du Lac county’s hunters to get their deer tested to help the agency track CWD’s presence and prevalence.
Unlike Colorado, the agency’s CWD plan won’t try to reduce deer densities, tell hunters to shoot more bucks, identify and target CWD hotspots for increased harvests, or require hunters to get their deer tested.
No, the DNR won’t ask deer hunters to do the hard things. It won’t even force-feed them, the NRB or our elected dunces science-based facts for fear they can’t handle simple truths.
Failing leadership, you’d wish the DNR would at least tell people we won’t solve CWD by simply increasing our wolf population. Contrary to current mantras, science hasn’t proven wolves to be nature’s meat inspectors.
Yes, wolves remove sick deer from the landscape because they often catch the weakest, least-aware, most vulnerable prey when taking chase. But that doesn’t mean wolves rid the land of CWD. An ongoing Montana study sure hasn’t proven that, at least not yet.
And as Heffelfinger noted in a July/August 2019 Mule Deer Foundation article, one study using a computer-simulated model found wolves could eliminate CWD, but other studies of actual mountain lion predation provided no evidence they helped control it. In fact, research shows that wolves scavenging CWD-infected carcasses carry infectious prions in their poop at least three days. Imagine how far they could spread those prion-laden turds across our landscapes.
Let’s face facts: CWD will never disappear or be controlled by ignoring it or delegating our management duties to four-legged predators.
An in-depth study covering five Western states and the province of Alberta found that CWD rates declined in mule deer herds when hunters increased an area’s buck harvest. — Patrick Durkin photo