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Do we have too many deer?

Ann Arbor deer aerial survey 1
Ann Arbor deer aerial survey 2

Ann Arbor's Aerial Surveys

(Click the images to expand)

Research indicates that aerial surveys are more accurate when conditions are clear and 2 observers were used. Ann Arbor conducted 2 surveys; both with 2 observers under good conditions (leaf bare trees and snow on the ground for contrast). Research indicates helicopter survey counts of deer during periods with snow cover can be very reliable.

Ann Arbor conducted two aerial surveys to count deer, costing the City $2,200 each. The February 10, 2015 survey counted 116 deer, including 32 on the border or outside of Ann Arbor. The March 6, 2015 survey counted 168 deer, including 91 on the border or outside of Ann Arbor. According to the 2010 US Census, the city of Ann Arbor is 27.83 square miles, with 4,093 people per square mile. City Council approved a cull in Wards 1 and 2. Ward 1 is approx. 6.6 sq miles; the aerial surveys indicate an average deer density of 4.4 deer per sq mile. Ward 2 is approx. 8.6 sq miles, and if deer who are on the border are counted, has an average deer density of 8 per square mile.


These indicate Ann Arbor has 3-8 deer per square mile; Ward 1 has about 4 per square mile, and Ward 2 has about 8 per square mile. 


According to an Ann Arbor City Council report, Michigan Natural Feature Inventory (MMFI) Biologists recommend deer densities of 15-20 deer per square mile, and "Scientific studies indicate deer densities of 15-20 per square mile or less are considered a more optimal level for public health (e.g., tick population), safety (e.g., traffic collisions) and landscape management purposes."


Even if the surveys missed half of Ann Arbor's deer -- even allowing for a 100% undercount -- Ann Arbor would still be well under experts' recommended deer density.

Furthermore, a Cornell study, often cited by those who want a cull in Ann Arbor, suggests 20 deer per square mile as well.


Authorities recommended a deer cull on Jekyll Island in Georgia, where it was estimated they had 76 deer per square mile. Yet they haven't done one; residents have criticized the plan as an embarrassment.


Michigan DNR remains "neutral" on a cull in Ann Arbor. Perhaps that's because they say deer numbers are declining in Michigan.



Ann Arbor deer

The Quality Deer Management Association (QDMA), a national group of hunters, suggests that deer populations are declining across the US, and that Michigan's deer harvest has declined 20% from 2003 to 2013.

The Michigan Department of Natural Resources (MDNR)'s 2014 Deer Management Overview for Washtenaw County says, "It does appear that deer herd condition declined in the Washtenaw DMU [Deer Managment Unit] from 2003-12. Increased deer

density resulting in heightened intra-species competition and resource depletion can cause this phenomenon. However, as most of our deer population indices point to a decline in deer numbers, this seems unlikely to be the cause. Also, environmental influences (e.g., extreme weather events) tend to be short in duration and impacts are limited to short time frames (i.e., 1-2 years). We would not expect to see environmental effects drive down deer condition for this time span, although climate change may be shifting this perspective. Most likely, the reduction in deer condition is mainly attributable to land use changes. Increasing development across the DMU often can help increase survival of deer using nonhuntable lands as refuge, but it may come at a price of natural vegetation resources."


We do not have a deer overpopulation problem in Ann Arbor.


Ecologists say that if there were truly overpopulation, in the sense of overburdening the habitat, deer would starve en masse, as occasionally occured decades ago when winters were more severe and browse was less available. Does would no longer have twins, and deer numbers would drop within a year. But deer aren't overburdening the habitat-- because we're creating more. Now, urban and suburban landscaping is providing more and more deer habitat.


The problem is not "too many deer," but rather "too many deer where some people don't want them to be."


And though we can sympathize with gardeners' and landscapers' concerns about deer in their backyards, a cull won't solve the problem-- and may worsen it. Cullers cannot guarantee the removal of specific deer deemed nuisances, and if choice landscaping/food sources remain accessible, deer will continue to thrive on them.


Scientific studies indicate culling can increase birth rates.


Culling only lowers deer numbers on a temporary basis, which is why it must be done year-after-year. Fairmount Park started a "one-time" deer cull in 1999; they're now on their 15th year of culling. Jackson is on their 8th.


Reproduction is density-dependent; as the total deer population decreases, the average number of offspring increases. After culling in Chicago's metro area, ecologists were dismayed to find that does in these culled areas were more likely to reproduce at a younger age, more fawns were born and more survived. Scientists in Florida have found hunted deer herds are much more likely to produce twins. 


When deer populations are unnaturally reduced (e.g., through a cull), yet resources remain, the remaining deer and those who move in to take those resources are better-nourished. Better-nourished deer have higher productivity, lower fawn mortality, increased conception rates, and increased pregnancy in young deer--thus helping the population grow unnaturally faster.

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