Deer Abundance and Densities in Wisconsin Deer Management Units

The Wisconsin DNR annually estimates the size of the population of deer in each deer management unit. Deer population estimates may be expressed in terms of abundance or density. Abundance estimates are the total number of deer estimated for an entire unit. Density can be calculated by dividing the abundance estimate by the area (square miles) within the unit. Density estimates are useful for comparing population estimates among deer management units because they standardize abundance estimates by taking into account the difference in size of deer management units.

Deer population estimates are made for two time periods, a fall or prehunt estimate and an overwinter or posthunt estimate. Posthunt population estimates are annually compared to the deer population goal for each deer management unit as a basis for annual adjustments of antlerless harvest quotas. Population goals and density estimates are usually expressed as deer per square mile of deer range (i.e., suitable habitat).

Fall abundance estimates are based to a large degree on the number of antlered bucks harvested in each deer management unit. Buck harvest density in 2008 varied among deer management units from less than 1 to 9 bucks harvested per square mile of deer range. Fall deer densities in 2008 varied from 8 to more than 100 deer per square mile of deer range. Deer management units with the highest fall densities were mostly in the east-central and southern parts of the state. Units with the lowest fall deer densities were mostly in northcentral and northeastern Wisconsin. Overwinter deer population estimates are derived from the fall population estimates and the total registered harvest. Overwinter deer densities in 2008 varied from about 7 to more than 100 deer per square mile of deer range.

Deer range is used for determining population goals and density because it provides a standard for comparison of density among deer management units and it helps biologists to understand the ecological and economic effects of different deer densities. The amount of deer range varies greatly among deer management units. In some northern units, more than 95% of the land area is classified as deer range. In contrast, less than 25% of some of the highly urbanized and/or agricultural units in the south is considered to be deer range. The variation in the amount of deer range across the state may be one of the factors that contributes to confusion about deer population estimates.

Deer population and harvest densities can also be expressed in terms of total land area. This results in a somewhat different picture of the distribution of deer in Wisconsin. Deer management units in which a small percentage of the total land area is classified as deer range may show a high number of deer per square mile of deer range but a lower number of deer per square mile of land area. Using land area as the basis, the harvest density of antlered bucks in 2008 varied from less than 1 to nearly 6 bucks harvested per square mile of land area. In many deer management units in southeastern and southwestern Wisconsin and in several units throughout northern Wisconsin, fewer than 2.0 bucks were harvested per square mile of total land area. In contrast, more than 4 antlered bucks were harvested per square mile of land area in several west-central and east-central deer management units. Based on land area, fall 2008 densities were highest in east-central and west-central Wisconsin and in a few units in southwestern Wisconsin. By comparison, fall densities were much lower in southeastern and extreme southwestern Wisconsin and in a few northern management units. Overwinter deer densities showed a similar geographic pattern.

It is important to keep in mind that density estimates for deer management units are based largely on the number of antlered bucks harvested in the unit. The resulting density estimates are averages for the entire unit and may not accurately reflect local deer density. There can be considerable local variation in density within deer management units due to differences in deer habitat quality and local hunting pressure.

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