Anderson: DNR official, bowhunting advocate discuss deer management

Brooks Johnson, president of Minnesota Bowhunters Inc., believes the state's whitetail herd has been reduced in number too far, through mismanagement or intentionally, because the Department of Natural Resources weighs too heavily complaints it receives from various non-hunting factions about the herd's size.

In the next legislative session, Johnson will seek support for an examination of DNR deer management — in ways similar to the ways deer management was reviewed recently in Wisconsin.

To further discussion about deer-management on the eve of the state's 2014 whitetail season, I asked Johnson to offer some questions he has about DNR deer administration. In turn, I posed the questions to DNR big game program leader Leslie McInenly.

Their give-and-take appears below.

Johnson: Beginning about 15 years ago, the DNR decided to reduce the size of the deer herd. Why?

McInenly: For much of the 1970-1990s, our management was designed to build deer numbers and the population responded. By the early 2000s, there were concerns regarding impacts of higher deer densities (e.g., deer browse impacts were specifically identified as a problem that required correction to maintain forest certification). DNR recognized the need to have a broad, public discussion about deer population goals and, in the interim, began to reduce deer densities as we developed the process. The first goal-setting effort occurred in 2005 and used a combination of stakeholder advisory teams and public input. Various factors were considered, including the economic and social value of deer, habitat quality and food resources, deer vehicle collisions, agricultural depredation, browsing impacts on native plants and other wildlife, disease and health concerns, and historic deer population and harvest trends. The process specified the desired population direction and magnitude of change for each permit area.

Johnson: This year's deer harvest might be the lowest in 32 years. Does this mean the DNR deer population model doesn't work well?

McInenly: High harvests during the past decade (supported by higher bag limits and the availability of antlerless permits) were intentional to move the population lower, toward publicly set goals. Now we've heard from hunters who feel deer numbers are too low. So this year's harvest was designed to boost the population. That said, we don't look only at our model's population estimates to determine harvest strategies. We look at a suite of indices [primarily harvest data but including population trends] and supplementary information to assess whether populations are increasing, stable, or decreasing. From a biological perspective, Minnesota collects more data and puts more effort into validating modeled populations than many other Midwest states.

Johnson: Periodically, the DNR uses aerial surveys to validate deer numbers estimated by its population model. Are such flights used often enough to check and, as necessary, re-calibrate the population model?

McInenly: Our population model is reviewed annually and, if needed, recalibrated using harvest statistics. Ideally, an independent method (e.g., aerial survey) should be used every five years to assess model performance. But available resources, weather and other survey needs can limit their frequency. The important thing is to understand that the model doesn't need to provide an exact count of deer to help monitor population trends.

Johnson: Some hunters point to Camp Ripley to underscore their belief that DNR deer management is misguided. Historically, Ripley has had one of the country's most trophy-rich and abundant whitetail herds. Now the herd is depressed, and hunt applications were down 30 percent this year.

McInenly: The more conservative management strategy at Camp Ripley this year, including a bag limit reduction and a reduction in the total number of permits available, likely impacted participation and harvest. The Ripley hunt was also likely impacted by a date change that moved the first hunt from the Thursday/Friday of MEA weekend to a Wednesday/Thursday that didn't coincide as well with the traditional dates when kids are out of school.

Johnson: DNR deer population management was once dependent largely on science, but now includes social considerations, such as deer-vehicle collisions and crop losses. Why?

McInenly: I would argue we still use science to inform our deer management and that social considerations have always played a role in population management. We are probably just more direct in acknowledging the need to balance social considerations. That includes the desires of farmers, foresters, ecologists or others who experience conflicts with deer and may favor lower deer densities in addition to desires of hunters, wildlife watchers and others who may support higher deer densities.

Johnson: Some states use deer-vehicle collisions as a primary indicator of herd size. Minnesota statistics show 50 percent fewer such vehicle-deer crashes than 10 years ago. Does the DNR use similar data in setting the state's herd size?

McInenly: We don't use deer-vehicle collision data to evaluate deer population trends, although we recognize public safety as a factor we should consider. We have found that reporting rates are inconsistent across jurisdictions and there is also variability in travel data unrelated to deer densities (e.g. gas prices and weather conditions during major travel dates) which is why we rely on other data sources, such as Minnesota's mandatory harvest registration.

Johnson: The DNR in part justifies its recent deer herd size reductions on crop depredation and car-deer collisions. But by my estimate deer consume less than .5 percent of state crops and represent 2 percent of vehicle collisions. Given this, is it appropriate to weight these factors so heavily in the deer-population goal-setting process?

McInenly: The DNR doesn't attribute any particular weight to various social factors. Our approach is to try to balance concerns through the public goal setting process. That means providing an opportunity for all stakeholders to weigh in.

Johnson: The DNR doesn't track crop depredation and vehicle-deer collision reductions resulting from deer herd size reductions. Shouldn't it, in order to determine whether herd reductions significantly affect crops losses and deer-vehicle accidents?

McInenly: We could try to quantify every component associated with deer management, but we have to prioritize how we invest resources. Research staff is looking at measures of crop depredation, but it's challenging to do statewide. Social carrying capacity [SCC] reflects the [positive or negative] impacts deer may have on people and the things people value. The challenge is that people's tolerance varies depending on their social context. If your livelihood depends on growing a crop, your SCC is very different from that of an avid deer hunter.

Johnson: Does the DNR know the deer carrying capacity, based on available habitat, of the state's various deer permit areas? If so, shouldn't this number be shared with citizen groups the DNR is now organizing to establish new deer population goals?

McInenly: The term carrying capacity must be defined to be useful, as there are a range of common applications. Biological Carrying Capacity [BCC] is the maximum population of a particular species a given area of habitat can support over a given period of time. In Minnesota this is a function of both habitat quality [primarily food] and climate. Measuring BCC is very difficult. Some studies have estimated BCCs for specific Midwest sites. But the information isn't easily applied to Minnesota deer permit areas. Still, it could help inform the discussion.

Dennis Anderson • danderson@startribune.com