Editor’s Note: This is the second in a two-part series on the deer population. Last week’s installment focused on the impact of declining habitat quality. This week, we look at the impact of wolf predation and the quality of the DNR’s deer population modeling.

Step into any bar in the North Country, buy a guy a beer, and ask him what’s ailing the region’s deer population. Nine times out of ten, he won’t even hesitate to identify the problem— wolves. In some ways, your new barstool buddy would have a point, albeit an incomplete one.
A 2020 DNR study of deer mortality in two locations in northern Minnesota, including near Elephant Lake north of Orr, research biologists Glenn DelGiudice and Bradley Smith found that wolves took an average of 30 percent of adult does annually during the course of three winters. Their take of adult bucks and fawns was presumably higher than that.
Even the researchers expressed surprise at the high percentage of wolf kills.
For critics of the DNR and its deer management, the study results provided evidence that the agency was underestimating deer mortality in its population modeling. I mentioned Randall Tlachac in last week’s installment and as part of our ongoing correspondence, he requested more information on the deer population modeling that the DNR undertakes every year as part of establishing bag limits for the fall hunt. He asked for specific mortality estimates from the model for several deer permit areas in northeastern Minnesota, including some in our area, and it was clear that the mortality rates that the DNR model employs don’t line up at all with the mortality rates their own 2020 study suggested.
The model adjusts its projected winter survival based on the winter severity index, but even in severe winters the model does not appear to be assuming mortality that lines up with the findings of the 2020 study. Granted, it’s one study with a relatively small sample size (based on GPS-collared female deer), but it should have prompted a re-examination of the DNR’s modeling.
Tlachac certainly isn’t the only one to question the apparent disconnect between the model and the facts on the ground. In a 2016 review of the DNR’s deer management, the state’s legislative auditor concluded that the model was basically sound but recommended that the agency “improve its resources for estimating deer populations; specifically, DNR should conduct field research to collect and utilize more information about Minnesota’s deer, and to validate DNR deer population estimates.”
The 2020 DelGiudice study was undertaken in response to that recommendation, but it appears that the study’s findings have not been incorporated in any meaningful way into the DNR’s population modeling. DNR officials claim that the model’s use of the winter severity index reading does account for wolf mortality, but even under the worst WSI reading, it does not appear the model incorporates anything close to the mortality identified in the 2020 study, which was done during a period of relatively average winters.
The DNR, back in June, announced that it is undertaking a new study in St. Louis County and several other northern Minnesota counties to try to better determine deer densities in these areas to see how well they align with the DNR’s modeling. They are also planning to explore how deer populations might differ on public lands versus private, since those lands are currently managed differently, as I discussed in last week’s installment in this series.
We will certainly be reporting on the results of that research once it’s available.
Does it matter?
If the DNR’s modeling is, in fact, underestimating deer mortality in our region, it could mean that the DNR is setting bag limits that are higher than the population can support. Yet I spoke to Eric Michel, the DNR’s modeler, who told me that bag limits are determined mostly by area wildlife managers, based on several factors, including harvest data from previous years, previous winter severity, field reports, and hunter observations. “We’re not relying on the population model for what we’re going to do in the fall,” he said.
Yet the debate over the model could well be a distraction in the overall discussion about wolves and deer, particularly if it doesn’t play a major role in determining the bag limits for the fall hunt. And here in our region, the DNR has already accounted for the recent relatively high mortality (from all sources) in our region, by shifting to bucks-only, which sharply reduces the population impact from hunter harvest.
Finding the variable
What we know for sure about the deer population in our region is that it has varied tremendously over the past 20 years. Back in the mid-2000s, we had record numbers of deer in our region, while numbers have dropped considerably (but nowhere near record lows) in more recent years.
In determining the causes for such fluctuations, it is useful to look for a variable or variables that fit those population trends. As I demonstrated last week, there appears to be a strong correlation between the deterioration in deer habitat that I documented through inventory data and the resiliency of the deer population.
To claim that wolf predation was the primary cause of the decline in our region’s deer population from record numbers in the mid-2000s to the lower numbers we see today, we would need to have data that would correlate the trends we’ve seen in the deer population with similar changes in the wolf population. For example, we would need to show that wolf numbers have increased significantly in our region over that time frame, since presumably the average wolf here isn’t eating any more deer than it did in the past. If anything, they’re eating fewer because deer are scarcer.
While range expansion has had impacts in some areas, mostly on the southern and western fringes of wolf range, the data from numerous surveys and population estimates from both state and federal researchers simply does not show an increase in wolf numbers in our region over the past 20 years.
The wolf population in northern Minnesota has been studied intensively since the 1970s and the DNR regularly collects data on about 40 GPS-collared packs, determining the size of the packs and their territories. Those data show that pack size in Minnesota has been remarkably stable at around five wolves per pack on average.
The number of packs did grow initially as bounties were ended and federal protection took effect in the 1970s. By the end of the 1980s, the data show the number of wolf packs statewide at 233. By 2003-04, the number of packs had grown to an estimated 485, but have remained within a relatively narrow range since and have shown no upward change.
The growth in the number of packs has occurred almost exclusively from the expansion in wolf range that occurred in the 1980s and 90s, with only marginal expansion since. In our region, virtually all of the landscape has been occupied by wolf territories more or less at carrying capacity since at least the 1990s. Perhaps not surprisingly, the DNR’s highest estimate of the wolf population occurred in 2003-04, at right around 3,000. That coincided with the highest deer densities we’ve seen in the region in decades.
None of this is a surprise. Voluminous research on predator-prey relationships show that predator populations have a limit that is defined largely by the density of their prey populations. When deer numbers decrease, as they have recently, we would expect to see wolf numbers fall as well.
Indeed, that’s what researchers with the Voyageurs Wolf Project stated just last week in their annual report. For the second year in a row, the researchers found that the wolf population within their study area (which encompasses 24 pack territories) had declined, this year by about 15 percent. Given the recent reductions in the deer population, this would be expected.
Wouldn’t a wolf hunt help deer?
Many deer hunters have argued for a wolf hunting season, believing that is the best way to help boost deer numbers. While it’s certainly a popular idea with many hunters, there is virtually no science to suggest it would prompt a noticeable increase in our deer population. Wolves have a reproductive capacity that generally far outstrips their actual reproduction, which is typical of predators at the top of the food chain. The limits of prey availability and pack dynamics combine to limit wolf populations to the carrying capacity of the landscape they inhabit.
Randomly removing 20 percent of wolves a year from the Minnesota population might please many hunters, but fewer wolves (and fewer mouths to feed in a given pack) would generally allow for greater pup survival the following year and ultimately have little impact on deer numbers. Again, it’s about carrying capacity.
We don’t have to speculate on this. Keep in mind, Minnesota did have a wolf season for three years, from 2012-2014, during which a total of 923 wolves were registered by hunters or trappers. A total of 413 wolves were registered in the fall of 2012, a number equal to about 15 percent of the estimated wolf population at the time. That following winter was moderately severe based on the winter severity index, but was mild compared to the 2013-14 winter, which took a real toll on deer. Did the 2012 wolf hunt help the deer recovery? Based on harvest data from the fall 2013 hunt, the answer is a clear no. Indeed, deer registrations in Zone 1 fell from 58,947 in 2012 (before the impact of the wolf hunt) to 49,156 during the 2013 hunt. In other words, we took 15 percent of the wolves off the landscape heading into a moderately severe winter and saw hunter success decline by 16 percent the following year.
Another 238 wolves were removed in the fall of 2013 and yet we saw the deer population collapse following the historically severe winter 2013-14 winter. (See Figure 1). That shows a clear correlation to winter severity, but no apparent correlation to wolf population.
There’s more data as well. We have an excellent comparison population right across the border in northwestern Ontario, where there is similar habitat and similar density of deer as what we see in our area. The only difference is that wolves have been hunted on the Canadian side of the border for decades. Yet as we can see from Figures 2 and 3, the hunter success in the area just north of the border tracks almost exactly with hunter success in the six deer permit areas in northern St. Louis, Lake, and Koochiching counties. Again, wolf hunting versus wolf protection appears to make little discernible difference to hunter success. I know that many advocates for wolf hunting don’t want to hear this, but it is what the data shows.
What’s the right number of deer?
All that we’ve reported here over the past two weeks is written from the perspective of a deer hunter. For those of us who hunt, more deer is generally seen as better. But that’s far from a universal opinion. Farmers and gardeners will have a different perspective. Insurance companies, who pay out millions in Minnesota every year in deer collision claims certainly aren’t going to advocate for more deer, nor are many drivers who’ve had literal run-ins with a whitetail.
As part of my background work for this series, I spoke to John Pastor, a retired UMD biology professor, who noted the impacts that our still relatively robust deer population has on our region’s forests. The presence of deer has made the white cedar little more than a legacy species that will eventually disappear from our landscape since it is almost impossible to regenerate in the presence of deer due to heavy browsing of seedlings. The restoration of white pine is also severely complicated for similar reasons.
The mid-2000s peak of the deer population also coincided with the start of the sharp decline in the region’s moose population. That’s no surprise given that deer are carriers of at least two parasites that are debilitating or fatal to moose. Given lower deer numbers in recent years, we see the moose population has stabilized.
While the DNR generally focuses on the desires of hunters, who pay license fees that support the DNR’s work, it’s worth remembering that fewer than ten percent of Minnesotans hunt deer. There are many more Minnesotans who have differing desires and values when it comes to the management of wildlife in the state. To what degree do the roughly 92-percent of Minnesotans who don’t hunt deer have a voice in this debate? It’s food for thought.