The MDNR does not have a recommended deer density in urban areas. Rather, we ask local elected officials to determine which level to manage their deer; either based on observed biological impacts to forests or natural areas, or social tolerances, which are generally met sooner in an urban setting. This allows them options in evaluating input and determining whether deer are having an unacceptable impact amongst residents in the community. This is generally done through one or a combination of several methods: monitoring deer-vehicle collisions, tracking resident complaints, surveying residents, habitat or regeneration impacts to forest/nature preserves, etc. If the elected officials deem that deer are a problem in their community, we are happy to work with them and provide recommendations to alleviate these conflicts. Typically, if conflicts are occurring at unacceptable levels across a broad expanse of the city, which limits the effectiveness of deer exclusion, lethal measures are typically recommended.
The helicopter survey should not be considered a census or indicator of herd density. The reason is that this is simply a count that occurs at one moment in time, and the estimate of how many deer were not seen is unknown. Without an effective estimate of how many deer were missed on the flyover, the count alone has little value. If this survey is repeated every year in the same manner, then Ann Arbor would be able to track changes in the deer population, and this in turn can be related back to management actions or strategies. So, the count that was conducted previously does have value, but only when it is included as a series of data points collected over time.
Deer, Elk, and Moose Management Specialist
Michigan Department of Natural Resources