Factors Affecting Mature Buck Harvest: APRs, Regulations, Access, Disease?

By Dr. Russ Mason

Across North America (albeit not in the Midwest), record book entries show a gradual decline in antler size scores for white-tailed deer. Factors contributing to this disturbing trend aren’t clear. West of the Mississippi, possibilities include invasive species and predator impacts, intrusive energy development and accelerating fire cycles. East of the Mississippi, declines could reflect changing habitat quality or the influence of various harvest regimes. Antler point restrictions (APRs), bag limit constraints and shortened harvest seasons are traditional topics of concern.

Surprisingly, few rigorous evaluations have been provided for fact-based critical discussions.

This partially reflects difficulties in identifying datasets with sufficient reach, both geographically and across time. One recent and relatively large-scale evaluation by the Michigan Department of Natural Resources has suggested that while APRs do (slightly) increase the age structure of deer populations, the effects were only marginally greater than the age structure of harvested bucks in matched control areas. Antlerless harvests were not meaningfully impacted by the APR restrictions (i.e., hunters did not shoot more antlerless deer in response to fewer legal bucks). Likely, these results reflect ongoing attitudinal changes; growing numbers of deer hunters voluntarily pass younger bucks, and, at least in Michigan, hunters aren’t especially interested in shooting does.

The DNR findings mirror the results of another Michigan study conducted by the Boone and Crocket Quantitative Wildlife Center (QWC). In this earlier examination, QWC examined harvest data from 23 counties in the northern Lower Peninsula of Michigan. Roughly half of these counties had APRs imposed, while the others did not. As expected, APRs were associated with the increased age structure of bucks in affected counties. Anecdotally, there were increases in hunter satisfaction. However, there were no statistically apparent differences in hunter participation between counties with or without the APR restriction, and decreased opportunities to harvest bucks in APR counties were not associated with any significant increase in antlerless harvest.

A third study, also by the QWC, substituted record book entries for the occurrence of older aged bucks in various locations. Using this indicator data, the QWC searched for relationships between the frequency of record book occurrences and various habitat features and regulation strategies across Midwestern states.

Although there were various expected differences across geographies, one unexpected result was a significant negative relationship between forest cover and antler size. Specifically, as cover increased, antler scores decreased. One possible explanation is that deer in high forest areas are nutritionally limited. Of course, another more mundane possibility is that deer with big antlers (or perhaps any deer) are harder to kill in the woods.

In terms of regulations, per se, record book entries suggest that any strategy that reduces buck harvest is associated with an increase in record book entries. Selective strategies (i.e., those that protected only a segment of the buck population) were no more effective than non-selective strategies. APR regulations were associated with a 50% increase in record book entries. Yet, non-selective strategies like one-buck rules and short seasons were also associated with more record book entries. In fact, the biggest increase was associated with short seasons: six-day seasons had more than twice as many record book entries as 33-day seasons.

These three evaluations suggest:

First, any regulation limiting buck harvest will likely enhance age structure in the affected population. Among the regulation types evaluated, short hunting seasons were correlated with the most significant impacts on buck age structure, even though hunters are not required to do anything differently.

Second, the findings unambiguously support the argument that changes in deer hunting opportunities are not coupled with changes in participation.

This (somewhat disturbing) possibility is consistent with studies of waterfowl hunting. Other factors, including tradition, personal beliefs and mistrust of experts and institutions, may be as (or perhaps more) important. They are also consistent with the growing consensus among professionals that regulations only impact harvest when hunters want more than the resource can provide. In other words, hunting regulations are substantially less effective in modulating harvest when harvest opportunities are abundant and hunter numbers are diminished.

An important and obvious question is why (in the face of these data) agencies continue to entertain tests of demonstrably ineffective regulatory packages. The most likely explanation is that politically influential hunter organizations, sometimes in partnership with state officials or wildlife commissions, insist that their preferences and personal intuitions, not the available science, should dominate (regardless of the science or the preferences of others).

One of the principal tenets of the North American Model of Wildlife Conservation is that “Science is the Proper Tool for Discharge of Wildlife Policy.” Of course, this does not mean that science should be the only consideration — but it does mean that science needs to be included.

Today, social considerations and human dimensions research are all the rage. However, that doesn’t mean that social considerations are more important than empirical biological information, nor that they dominate decision-making. This is especially true when those social preferences have predictably negative impacts on herd health (i.e., APR regulations almost certainly accelerate the spread of CWD without impacting the deer densities that affect CWD prevalence).

As state fish and wildlife agencies lean ever more heavily into their recreational responsibilities, there are, arguably, increasing risks to fish and wildlife conservation.
More broadly, it raises a substantially more troubling concern: are hunters conservationists, as many of us like to claim, or simply outdoor recreationists relatively unconcerned with the impacts of their activities?

Editors Note: In 2024, the Michigan Department of Natural Resources announced the creation of the Deer Managment Initiative.

The Deer Managment Initiative will include:

Upper Peninsula and Lower Peninsula workgroups, including traditional stakeholders and non-consumptive users. 

The DMI’s responsibilities:

1) Help develop a broad survey about deer trends (distributed to hunters and nonhunters).
2) Hold a several-day meeting to digest data, identify trends or problems and develop recomendations.

Dr. Russ Mason is a faculty member at the University of Minnesota’s Center for Infectious Disease Research and Policy. He helps lead efforts funded by the Minnesota State Legislature to explore the social, economic, and human health consequences of a CWD spillover event into livestock or humans.