Summary

In January 2016, the city began a two-month deer cull. City council hired sharpshooters to kill deer in parks on the north side of the city. 14 parks were closed to the public on weekdays after 4:00 PM.

Some people argue that the city should continue culling for several years to prevent car accidents and vegetation damage. Others argue that culling is dangerous, cruel, and unnecessary. In my view, the two most important questions in this debate are:

Is it ever justifiable for the city to cull deer?
If so, what circumstances justify culling?

In my opinion, culling deer is sometimes necessary, but the city should only cull to carry out an intelligent plan. So far, I don’t think the city has a good plan. To make one, it should follow these steps:

Make a goal.
Measure whether the goal is being met.
If the goal is not being met, and non-lethal methods are insufficient, cull at night, but do not close parks before 10:00 PM.

I would like to hear your thoughts about deer management. Please email me at will@willleaf.com

Background

There are probably several hundred deer within Ann Arbor.

City staff counted deer by helicopter in March, 2015, and found 168 in the city limits. The cull in January and February 2016 killed 63 deer. On February 18th, near the end of the cull, the city did another count and found 202.

It is not clear how many deer are in the city, but there are at least a few hundred. Most of the deer are in the outer parts of the first and second wards. These areas have lots of parks and low-density suburban homes. White tailed deer thrive in these areas, because suburbs have plenty of low-hanging vegetation but no predators. This kind of habitat has grown rapidly over the last fifty years, so there are probably more deer in the city than there used to be.

How many deer are too many?

Some people I’ve talked to argue that there is a scientifically optimal amount of deer per acre, and the city should base its policies off this number. I disagree. Instead, I think the city should focus on addressing the problems that deer cause.

Judgements about deer numbers depend on human values.

There is no scientific way to determine the correct number of deer that should live in Ann Arbor. Instead, city council must use values to consider the pros and cons of having more or less deer in the city. For example, culling more deer would help oak saplings, but harm deer. There is no way to scientifically determine the relative worth of these species. Our values influence our choices, and reasonable people often have differing values. In philosophy, this is called the is-ought problem. Facts about how the world is cannot answer questions about how the world ought to be.

It is comforting to think there is some “balance of nature” to guide our decisions, but this concept is too vague to be a guide. Humans have been altering deer habitat in North America for thousands of years, even before European colonization, and there is no baseline number of deer to return to. Even without humans, ecosystems often change, and there is no way to determine what the “natural” equilibrium is. William Cronon‘s books go into this subject in more detail.

Because there is no objectively correct number of deer , The Michigan Department of Natural Resources, and other wildlife agencies, use a term called “social carrying capacity.” It means the density of deer that a human community will tolerate. It is different than “biological carrying capacity”, which means the number of deer that can survive in a habitat.

Deer densities change depending on how boundaries are drawn.

Even if there were a scientifically optimal deer density, it would not be obvious what boundaries to use when calculating it. Ann Arbor has a lower deer density than the first ward, and the first ward has a lower density than the outer first ward. It is not clear which area to consider. To me, it makes more sense to focus on the harms that deer cause. The optimal deer density on a highway is zero, but it is higher in a park where people enjoy seeing deer.

Deer cause various problems.

Car Crashes

There were 51 deer-related vehicle collisions in Ann in Arbor in 2014. One of these crashes resulted in a reported injury. In comparison, there were 3,827 total crashes in Ann Arbor the same year, in which 630 people were injured. Crash data suggests that the number of deer-related collisions is trending upward, from about 20-30 a year to 30-50 a year.

Update: There were 88 deer-related collisions in 2015. This is a large increase from prior years. The data comes from Dave Askins, the former editor of The Ann Arbor Chronicle, who got it from the Michigan Department of Transportation.

Garden Damage

When I campaigned door to door in 2015, I often went to the outskirts of the first ward near the highway. There, many people complained that deer were eating their gardens. They showed me their backyards where all the vegetation below five feet was barren. They point out damaged plants that were supposed to be deer-resistant. The city’s survey of residents shows many similar complaints.

Ecological Damage

A University of Michigan biologist, Christopher Dick, argues that deer are killing too many plant saplings, butterflies, bees, small mammals, amphibians and birds.

Some people are not bothered by these problems and enjoy seeing deer.

A number of people I’ve spoken with don’t mind the problems above. They enjoy seeing deer and feel that humans should coexist with other species. They understand that deer sometimes interfere with human activities but do not see this as a justification for killing them.

Response

Make a goal

Currently, the city’s goal is to reduce negative deer-human interactions. The problem with this goal is that it is not measurable, so the city can’t evaluate its own actions. It can’t answer basic questions like: How many deer should we kill? Did this year’s cull succeed? Are there better alternatives? To create a measurable goal, the city should create thresholds that state the circumstances that justify culling. Here is an example:

Culling Thresholds

There are more than 70 deer-vehicle collisions a year.
There is severe vegetation damage in one or more deer management district.

The city will continually use non-lethal methods to address deer related problems. If these techniques fail to keep deer problems under the thresholds above, the city will also cull.

To make thresholds like the ones above, council first needs to ask better questions of the public. The city should survey residents on what circumstances justify culling, rather than just ask whether they support “continued lethal methods.” Getting feedback will help council make a long term plan. Without a long term plan, residents will have to debate the same issue every year. If everyone has to reargue the same topic every year, many residents will eventually get fed up and stop sharing their opinions. Over time, the most dedicated interest groups will gain influence at the expense of the general public.

When choosing what thresholds to support, I would pay close attention to the opinions of first ward residents. There are some objectives I would oppose regardless of popular opinion, such as accepting 500 deer-vehicle collisions a year, or not tolerating minor vegetation damage, but there are many reasonable goals between these extremes, and I would get public feedback before choosing one.

Measure

Once city council has decided what conditions justify culling, city staff should measure whether these conditions exist. To measure the number of vehicle collisions, the city should continue to use data from the Michigan Department of Transportation.

To measure vegetation damage, the city should divide the city into deer districts and measure browsing damage in each. At first, the city could just have a botanist walk through each district, look at existing test sites, and judge the extent of plant damage. Eventually, the city could set up more test sites throughout Ann Arbor. The role of city staff would be to measure deer damage on a 1-10 scale and to explain what these numbers mean to the public. The role of city council would be to get input from the public, and then decide what level of damage justifies culling.

Respond

If the city’s deer problems are below the threshold for culling, the city should respond by using non-lethal methods. If deer problems are above the threshold, the city should use both lethal and non-lethal methods.

Here is my assessment of what responses would be effective and humane. If you disagree, or have information I don’t know about, please contact me.

Non-Lethal Methods

Fences

Effectiveness: Deer can jump fences that are up to eight feet high, but the city forbids fences above 4 feet for front yards, and 6 feet for side yards. It allows 8 foot fences for rear yards, but requires a building permit. I support raising the height limit for front and side yards, but even if the rules are changed, many people in the outer first ward live in homeowners associations, which often have extra rules about fencing.

Sterilization

Effectiveness: I went to a humane society meeting in May, 2015, where an expert in deer management discussed methods for reducing deer populations without killing. The two methods discussed were PZP birth control darts and surgical sterilization. Either approach would require the Michigan Department of Natural Resources’ consent.

There have been a few studies on controlling deer numbers with birth control and sterilization. Both methods seem to be effective at limiting deer numbers in closed environments, such as fenced areas and islands. There have been fewer studies on areas where deer can move freely. The study in the city’s report suggests that birth control is ineffective in free ranging deer populations. I don’t know of any studies that contradict this.

In February 2016, I emailed Chad Stewart, a deer, elk, and moose specialist at the Michigan Department of Natural Resources, and asked him about this subject.

Me: Would the DNR consider a sterilization plan? I understand that sterilization is probably not effective in free-ranging populations.

Chad Stewart: The Department has not authorized any sterilization plan. Again, that is not to say it couldn’t happen. It would likely be done under a research permit, and would need an experienced Principal Investigator associated with a University, describing the intent and purpose of the sterilization program. I would again advise that this technique has not proven successful in a free ranging environment. I would encourage you to research the Cornell deer sterilization project as a prime case study of how sterilization programs are unlikely to solve the problem.

Cruelty: It is possible to sterilize deer safely, but botched sterilizations are very cruel. Residents of East Hampton, New York are suing their village government over a recent sterilization program that may have caused does to die while giving birth to stillborn fawns.

Lethal Methods

Sharpshooters

Effectiveness: Shooting deer can quickly reduce deer numbers, but the population will rebound over time. The city will have to cull repeatedly. Also, sharpshooters will not be able to kill deer that roam around neighborhoods but do not enter parks, because state regulations prohibit people from firing guns at animals within 450 feet of occupied buildings, unless the owners of those buildings give consent.

Cruelty: A common objection killing deer is that it is cruel. I disagree. When humans shoot deer, deer suffer visibly. But without hunting, deer die from causes that are less visible, but probably more painful, like starvation, car collisions, disease, and coyote attacks. I think human beings bear some responsibility for these deaths, because we have created the conditions that cause them. We have built a city with attractive gardens, few predators, and lots of cars. If we refuse to kill deer under any circumstances, we might end up causing more suffering rather than less. For example, if ten years from now, deer are starving due to overpopulation, and non-lethal methods are not working, I think it would be cruel not to cull. There are plenty of reasonable objections to culling, especially the way it was done last year, but I don’t accept the argument that humans should never kill deer.

Here’s another thing to consider: When food banks receive thousands of pounds of venison, their customers will probably substitute venison for some of the other meat in their diet. Since meat production often involves raising animals in cruel conditions, it seems that a cull could prevent some cows, pigs, and chickens from suffering intensely.

Park Closures: One drawback of culling is that the city needs to close its parks while guns are being fired. I think the city made a mistake when it decided to close parks on weekdays at 4:00 PM last winter. The extra difficulty of culling only at night seems like a small price to pay compared to the cost of closing parks for a good chunk of the winter.

Darting/Euthanasia

Effectiveness: The city could shoot deer with tranquilizer darts, and then euthanize them when they are unconscious. The advantage of this approach is that it could be done all year round, without guns or park closures. I asked a deer specialist from the Michigan Department of Natural Resources whether this approach would be feasible. He said, “To my knowledge, no other communities in Michigan have adopted this approach. That is not to say it can’t happen or could not be allowed. I would have extreme reservations regarding the efficiency and cost of such a program, and would have no problem saying this in a public meeting.”

Cruelty: When deer are hit by darts, they fearfully run around before collapsing. Also, the tranquilizer drugs would make the venison inedible. For these reasons, I think a darting plan should only be used if non-lethal methods and culling both fail to keep deer problems under the city’s thresholds.

I emailed Chad Stewart, a deer specialist for the state government, and asked his opinion on darting.

Me: Would the DNR ever consider approving either of these actions:

Let the city dart and tranquilize deer within the city limits, and then kill the deer in some state-approved process.
Following a request from the city, allow Ann Arbor property owners to hire certified wildlife technicians to dart and tranquilize deer on their own property.

Chad Stewart: With darting, as you are proposing, there are several considerations to take into account. It’s possible we could permit individual landowners to remove deer from their property; we would have to review this on a case by case basis, and we would strongly encourage them to have some sort of agreement with their local unit of government. One problem is that there are very few qualified individuals who have the expertise and experience to adequately dart a deer, remove it from an area, and humanely euthanize it. I would doubt that these individuals would be find it economically advantageous to be brought in to work on one small parcel of property. In addition, the removal process would be extremely inefficient. While a shooter can take multiple deer out of a group within seconds, an individual can only dart one deer at a time. This leads to educating remaining deer in the group, causing them to avoid the property in the short-term. This could actually exacerbate the problem in the future. Finally, with immobilizing drugs recently entered into a deer’s muscle system, it is unlikely they would be accepted for venison donation at local hunger shelters.

Me: Would a city managed darting-euthanasia plan be feasible? The city might dart in parks, or on properties where the owners consent.

Chad Stewart: To my knowledge, no other communities in Michigan have adopted this approach. That is not to say it can’t happen or could not be allowed. I would have extreme reservations regarding the efficiency and cost of such a program, and would have no problem saying this in a public meeting.