Deer Herd Management: A vote for the ecosystem as a whole

Update November 2016: Research by Dr. Jacqueline Courteau analyzed grazing impacts of deer grazing on Ann Arbor parks. Based on her analysis of national data on temperate forests shows that deer browse damage of greater that 15% of oak seedlings inhibits forest regeneration. Her field work showed that deer browse damage in our natural areas is significantly above this level. You can read about her her research here.

UPDATE 12/19/2015 Part 1: Some have questioned the scientific basis for the cull. So, what does Professor Chris Dick,  Professor at University of  Michigan, Director of University of Michigan Herbarium, and Director of the E.S. George Reserve hear from his colleagues?
@ChuckWarp all #UMich biodiversity researchers I've spoken with support #A2council's vote for cull. Thanks for enduring the political heat!

The cull will be conducted by the USDA and in coordination with the Michigan Department of Natural Resources to ensure that is complies with all legal requirements and with the utmost commitment to safety.

UPDATE 12/19/2015 Part 2: There have been concerns raised by many, including those neutral to supportive of the cull, of the length of the park closings. When I saw the length of time for the closings, I too was taken aback. Staff worked hard to balance the needs for

  • Safety
  • Effectiveness
  • Park Access,

In that process, for the first  year of the cull there was a decision that it was very important to provide very clear, consistent, and highly cautious rules about park closures for the duration of the cull. The staff plan calls for closing 26 of the 73 parks and nature areas in Wards 1 and 2.

In response to the concerns, Councilmembers Sabra Briere and Chip Smith are bringing forward a resolution that would remove Argo and Bandemer parks from the cull (as parts of the Border-to-Border trail), Olson Park (at it is the city of the one of the City’s 2 dog parks), and Furstenberg park.

All parks affected by the cull will open again as soon as the cull completes, likely before March 31. Parks will remain open on Saturdays and Sundays.

Additional details about the closures, rationale, and safety precautions can be found at: http://www.a2gov.org/news/pages/article.aspx?i=210.


 

There has been significant discussion of the City Council vote to endorse a deer management plan that includes a deer cull.

First of all, I recognize that this is an issue that is deeply felt. Some are deeply against killing of animals for any reason. Others are against use of firearms in City limits under any circumstances other than law enforcement. These are fair and legitimate concerns that I have considered seriously in the discussion.

But they are not the only fair and legitimate concerns at play: concerns about car/deer collisions, concerns about public health, concerns about the long-term health of the deer herd, and others.

Those of us who have supported culling have been accused of doing it to save garden plants. For me, it is not about saving hostas.

For me, the most relevant other concern is the impact on our natural areas.

Is there a problem?

Some of the debate has been around if there is a problem in the first place. I believe there is. Recently a resident described seeing forty deer outside his window. That is not normal deer behavior. It is not healthy deer behavior.

Recently a fawn browsing at my workplace allowed me to get within six feet of it (I was too nervous to try to get closer). That is not normal deer behavior. It is not healthy deer behavior.

What’s more, there has been documentation of deer destruction to our natural areas. Kurt S., a park steward who is very active with natural areas restoration, recently challenged City Council and the community to find an unfenced oak seedling between 3 and 8 feet tall in the natural areas in wards 1 or 2.  He argued we wouldn’t find this next generation of the trees (for which Ann Arbor is named) because deer herds are too large and have browsed them all.

Nobody has yet met Kurt’s challenge.  [Update: As of November, 5, I have heard 2 accounts of people who have met the challenge. Of note, however, is that this was before the winter when browsing pressure increases. It will be interesting to see how many survive until spring.]

First of all, I recognize that this is an issue that is deeply felt. Some are deeply against killing of animals for any reason. Others are against use of firearms in City limits under any circumstances other than law enforcement. These are fair and legitimate concerns that I have considered seriously in the discussion.

But they are not the only fair and legitimate concerns at play: concerns about car/deer collisions, concerns about public health, concerns about the long-term health of the deer herd, and others.  For me, the most relevant other concern is the impact on our natural areas.

Is there a problem?

Some of the debate has been around if there is a problem in the first place. I believe there is. Recently a resident described seeing forty deer outside his window. That is not normal deer behavior. It is not healthy deer behavior.

Recently a fawn browsing at my workplace allowed me to get within six feet of it (I was too nervous to try to get closer). That is not normal deer behavior. It is not healthy deer behavior.

What’s more, there has been documentation of deer destruction to our natural areas. Kurt Sonen, a park steward who is very active with natural areas restoration, recently challenged City Council and the community to find an unfenced oak seedling between 3 and 8 feet tall in the natural areas in wards 1 or 2.  He argued we wouldn’t find this next generation of the trees (for which Ann Arbor is named) because deer herds are too large and have browsed them all.

Nobody has yet met Kurt’s challenge. .  [Update: As of November, 5, I have heard 2 accounts of people who have met the challenge. Of note, however, is that this was before the winter when browsing pressure increases. It will be interesting to see how many survive until spring.]

My own field observations back this up. My office is near a designated habitat area in Ward 1. Volunteers have put in tremendous work to clear out invasive species and to try to re-establish native plants. I myself have put in many hours uprooting buckthorn and honeysuckle. But all that comes back are more invasives. The native plantings are destroyed and, despite much hard labor, the understory layer remains dominated with invasive plants. Why? Deer overpopulation leads to overbrowsing and the destruction of native species.

These observations square with other ecologists observations of the effects of deer overpopulation.

The Audubon Society says:

“You have to protect yourself, your family, and native ecosystems from the most dangerous and destructive wild animal in North America, an animal responsible for maiming and killing hundreds of humans each year, an animal that wipes out whole forests along with most of their fauna. (http://blog.nature.org/science/2013/08/22/too-many-deer/)

A recent study of the impact of white-tailed deer on Bird Hills Nature Area, found:

This survey of 142 tree saplings (less than 2 meters tall) and shrubs in Bird Hills Nature Area shows that 80% have been browsed by deer, and 51% have half or more branches browsed. This level of browsing could interfere with forest regeneration and diminish the flowers and fruit available for birds, butterflies, and bees. Further monitoring would be necessary to track mortality, to reveal whether particular tree and shrub species of concern are browsed in future years, and to assess whether wildflower species are also being heavily browsed. (http://wc4eb.org/wp-content/documents/DeerBrowseBirdHills2015.pdf)

The local chapter of the Michigan Botanical Club recently reported:

Many of our members have lived in the Ann Arbor area long enough to have seen the dramatic declines in wildflowers in many of the treasured woodlots in the Ann Arbor area in recent decades. As deer exclosure experiments have repeated shown in Michigan and other areas, much of this loss, especially in sensitive plant groups like native orchids and conspicuous species such as trilliums and lilies, is due to excessively high deer populations.  The detrimental effects of high deer populations on tree reproduction are also well known, and deer are also implicated in disturbances promoting invasive species. This is all in addition to the considerable monetary impact that high deer populations have in destroying landscaping in resident’s yards and generating more numerous deer-car collisions, to say nothing of potentially entrenching Lyme disease in our area.

The Nature Conservancy observed:

In our opinion, no other threat to forested habitats is greater at this point in time — not lack of fire, not habitat conversion, not climate change. Only invasive exotic insects and disease have been comparable in magnitude. We can argue about which threat is more significant than another, but no one who walks the eastern forests today can deny the impact of deer to forest condition. (http://blog.nature.org/science/2013/08/22/too-many-deer/)

National environmental organizations have recognized the threat, and local field observations back it up. Deer overpopulation is a threat to the ecological health of our natural areas.

This should not be a surprise to us. Deer co-evolved with predators. We have increased deer habitat (more on that below) while also eliminating natural predators. A population explosion is too be expected. When this first came up I joked about bringing back wolves, but while deer thrive in a residential or office park-type ecosystem, wolves do not.

How to deal with the problem:

Believing as I do that there is a problem, the next question is “what to do about it?”

Option 1–Do nothing: Not taking steps to address the impacts on natural areas is a problem, though it would be one I am loathe to accept, but if the costs of management were too high, I might have to resign myself to the natural areas destruction from an excessive deer herd. (Strategies that have been discussed to address landscape damage or car/deer collisions such as fencing and planting deer-resistant species do not address the natural areas impacts).

 

Option 2—Deer Fertility Control: The Humane Society of the United States has supported the experimental use of deer fertility control methods such as immunocontraception or surgical sterilization of does.

Many other communities have tried these approaches (see for example the Cornell efforts, http://wildlifecontrol.info/deer/Documents/IDRM_12-5-2014.pdf). Some areas have seen some level of success with this approach when the herd is confined such as one found on an island. Despite many times it has been tried in free-ranging herds (such as the one here), I have found no evidence that it successfully lowers the deer population.

That said, I think there may be potential in using non-lethal methods to manage the size of the deer herd after it is brought down to an appropriate level. This is not a sure thing, the main drug used in immunocontraception is not legal in Michigan for this use and may actually make does into “buck magnets” by having them go through estrus but not become impregnated. The other main approach, surgical sterilization, is a costly endeavor (around $1,000/doe) and has its own set of ethical concerns.

Still, I supported efforts to explore these options. For my part, I would be willing to spend more money on fertility control efforts to maintain herd size (though not unlimited amounts more) if there is either strong evidence of their success in that role or an appropriately-designed research methodology that would evaluate impact while protecting the ecology of our natural areas.

 

Option 3—culling: The third option, a cull with professionally-trained sharpshooter under highly-regulated conditions outside of the hunting season, is the option that I joined the majority on Council in supporting to reduce the herd size.

Obviously, this brings with it many concerns. Some are opposed to any lethal deer management efforts, others are concerned about the use of firearms in the City. I get it. I work hard in my day job to help move forward common-sense gun regulations to prevent gun death and violence. I used to be a vegetarian (yes, I know I lose credibility in that statement with the “used to be.”)

That said, when I look at the evidence I see a deer cull as the most effective effort to protect our natural ecosystems, and the success of culls across the country supports this position. Culls also have an excellent safety record, and reducing the deer herd size will bring with it increased safety for motorists.

 

Development does not decrease deer habitat

In the debate, several have argued that we have created this problem by destroying deer habitat to make way for development. While development does play a role here, it is actually the opposite. Deer need both open areas for browsing and forested areas for cover. They do not thrive habitat this is all forest or all open field. So, residential and office park-style development actually increase deer habitat. According to an article in the New York Times:

Then suburbanization created a browser’s paradise: a vast patchwork of well-watered, fertilizer-fattened plantings to feed on and vest-pocket forests to hide in, with hunters banished to more distant woods.  (http://www.nytimes.com/2002/11/12/science/out-of-control-deer-send-ecosystem-into-chaos.html)

 

 

 

First of all, I recognize that this is an issue that is deeply felt. Some are deeply against killing of animals for any reason. Others are against use of firearms in City limits under any circumstances other than law enforcement. These are fair and legitimate concerns that I have considered seriously in the discussion.

But they are not the only fair and legitimate concerns at play: concerns about car/deer collisions, concerns about public health, concerns about the long-term health of the deer herd, and others.  For me, the most relevant other concern is the impact on our natural areas.

Is there a problem?

Some of the debate has been around if there is a problem in the first place. I believe there is. Recently a resident described seeing forty deer outside his window. That is not normal deer behavior. It is not healthy deer behavior.

Recently a fawn browsing at my workplace allowed me to get within six feet of it (I was too nervous to try to get closer). That is not normal deer behavior. It is not healthy deer behavior.

What’s more, there has been documentation of deer destruction to our natural areas. Kurt Sonen, a park steward who is very active with natural areas restoration, recently challenged City Council and the community to find an unfenced oak seedling between 3 and 8 feet tall in the natural areas in wards 1 or 2.  He argued we wouldn’t find this next generation of the trees (for which Ann Arbor is named) because deer herds are too large and have browsed them all.

Nobody has yet met Kurt’s challenge. .  [Update: As of November, 5, I have heard 2 accounts of people who have met the challenge. Of note, however, is that this was before the winter when browsing pressure increases. It will be interesting to see how many survive until spring.]

My own field observations back this up. My office is near a designated habitat area in Ward 1. Volunteers have put in tremendous work to clear out invasive species and to try to re-establish native plants. I myself have put in many hours uprooting buckthorn and honeysuckle. But all that comes back are more invasives. The native plantings are destroyed and, despite much hard labor, the understory layer remains dominated with invasive plants. Why? Deer overpopulation leads to overbrowsing and the destruction of native species.

These observations square with other ecologists observations of the effects of deer overpopulation.

The Audubon Society says:

“You have to protect yourself, your family, and native ecosystems from the most dangerous and destructive wild animal in North America, an animal responsible for maiming and killing hundreds of humans each year, an animal that wipes out whole forests along with most of their fauna. (http://blog.nature.org/science/2013/08/22/too-many-deer/)

A recent study of the impact of white-tailed deer on Bird Hills Nature Area, found:

This survey of 142 tree saplings (less than 2 meters tall) and shrubs in Bird Hills Nature Area shows that 80% have been browsed by deer, and 51% have half or more branches browsed. This level of browsing could interfere with forest regeneration and diminish the flowers and fruit available for birds, butterflies, and bees. Further monitoring would be necessary to track mortality, to reveal whether particular tree and shrub species of concern are browsed in future years, and to assess whether wildflower species are also being heavily browsed. (http://wc4eb.org/wp-content/documents/DeerBrowseBirdHills2015.pdf)

The local chapter of the Michigan Botanical Club recently reported:

Many of our members have lived in the Ann Arbor area long enough to have seen the dramatic declines in wildflowers in many of the treasured woodlots in the Ann Arbor area in recent decades. As deer exclosure experiments have repeated shown in Michigan and other areas, much of this loss, especially in sensitive plant groups like native orchids and conspicuous species such as trilliums and lilies, is due to excessively high deer populations.  The detrimental effects of high deer populations on tree reproduction are also well known, and deer are also implicated in disturbances promoting invasive species. This is all in addition to the considerable monetary impact that high deer populations have in destroying landscaping in resident’s yards and generating more numerous deer-car collisions, to say nothing of potentially entrenching Lyme disease in our area.

The Nature Conservancy observed:

In our opinion, no other threat to forested habitats is greater at this point in time — not lack of fire, not habitat conversion, not climate change. Only invasive exotic insects and disease have been comparable in magnitude. We can argue about which threat is more significant than another, but no one who walks the eastern forests today can deny the impact of deer to forest condition. (http://blog.nature.org/science/2013/08/22/too-many-deer/)

National environmental organizations have recognized the threat, and local field observations back it up. Deer overpopulation is a threat to the ecological health of our natural areas.

This should not be a surprise to us. Deer co-evolved with predators. We have increased deer habitat (more on that below) while also eliminating natural predators. A population explosion is too be expected. When this first came up I joked about bringing back wolves, but while deer thrive in a residential or office park-type ecosystem, wolves do not.

How to deal with the problem:

Believing as I do that there is a problem, the next question is “what to do about it?”

Option 1–Do nothing: Not taking steps to address the impacts on natural areas is a problem, though it would be one I am loathe to accept, but if the costs of management were too high, I might have to resign myself to the natural areas destruction from an excessive deer herd. (Strategies that have been discussed to address landscape damage or car/deer collisions such as fencing and planting deer-resistant species do not address the natural areas impacts).

 

Option 2—Deer Fertility Control: The Humane Society of the United States has supported the experimental use of deer fertility control methods such as immunocontraception or surgical sterilization of does.

Many other communities have tried these approaches (see for example the Cornell efforts, http://wildlifecontrol.info/deer/Documents/IDRM_12-5-2014.pdf). Some areas have seen some level of success with this approach when the herd is confined such as one found on an island. Despite many times it has been tried in free-ranging herds (such as the one here), I have found no evidence that it successfully lowers the deer population.

That said, I think there may be potential in using non-lethal methods to manage the size of the deer herd after it is brought down to an appropriate level. This is not a sure thing, the main drug used in immunocontraception is not legal in Michigan for this use and may actually make does into “buck magnets” by having them go through estrus but not become impregnated. The other main approach, surgical sterilization, is a costly endeavor (around $1,000/doe) and has its own set of ethical concerns.

Still, I supported efforts to explore these options. For my part, I would be willing to spend more money on fertility control efforts to maintain herd size (though not unlimited amounts more) if there is either strong evidence of their success in that role or an appropriately-designed research methodology that would evaluate impact while protecting the ecology of our natural areas.

 

Option 3—culling: The third option, a cull with professionally-trained sharpshooter under highly-regulated conditions outside of the hunting season, is the option that I joined the majority on Council in supporting to reduce the herd size.

Obviously, this brings with it many concerns. Some are opposed to any lethal deer management efforts, others are concerned about the use of firearms in the City. I get it. I work hard in my day job to help move forward common-sense gun regulations to prevent gun death and violence. I used to be a vegetarian (yes, I know I lose credibility in that statement with the “used to be.”)

That said, when I look at the evidence I see a deer cull as the most effective effort to protect our natural ecosystems, and the success of culls across the country supports this position. Culls also have an excellent safety record, and reducing the deer herd size will bring with it increased safety for motorists.

 

Development does not decrease deer habitat

In the debate, several have argued that we have created this problem by destroying deer habitat to make way for development. While development does play a role here, it is actually the opposite. Deer need both open areas for browsing and forested areas for cover. They do not thrive habitat this is all forest or all open field. So, residential and office park-style development actually increase deer habitat. According to an article in the New York Times:

Then suburbanization created a browser’s paradise: a vast patchwork of well-watered, fertilizer-fattened plantings to feed on and vest-pocket forests to hide in, with hunters banished to more distant woods.  (http://www.nytimes.com/2002/11/12/science/out-of-control-deer-send-ecosystem-into-chaos.html)

 

 

My own field observations back this up. My office is near a designated habitat area in Ward 1. Volunteers have put in tremendous work to clear out invasive species and to try to re-establish native plants. I myself have put in many hours uprooting buckthorn and honeysuckle. But all that comes back are more invasives. The native plantings are destroyed and, despite much hard labor, the understory layer remains dominated with invasive plants. Why? Deer overpopulation leads to overbrowsing and the destruction of native species.

These observations square with other ecologists observations of the effects of deer overpopulation.

The Audubon Society says:

“You have to protect yourself, your family, and native ecosystems from the most dangerous and destructive wild animal in North America, an animal responsible for maiming and killing hundreds of humans each year, an animal that wipes out whole forests along with most of their fauna.

A recent study of the impact of white-tailed deer on Bird Hills Nature Area, found:

This survey of 142 tree saplings (less than 2 meters tall) and shrubs in Bird Hills Nature Area shows that 80% have been browsed by deer, and 51% have half or more branches browsed. This level of browsing could interfere with forest regeneration and diminish the flowers and fruit available for birds, butterflies, and bees. Further monitoring would be necessary to track mortality, to reveal whether particular tree and shrub species of concern are browsed in future years, and to assess whether wildflower species are also being heavily browsed.

The local chapter of the Michigan Botanical Club recently reported:

Many of our members have lived in the Ann Arbor area long enough to have seen the dramatic declines in wildflowers in many of the treasured woodlots in the Ann Arbor area in recent decades. As deer exclosure experiments have repeated shown in Michigan and other areas, much of this loss, especially in sensitive plant groups like native orchids and conspicuous species such as trilliums and lilies, is due to excessively high deer populations.  The detrimental effects of high deer populations on tree reproduction are also well known, and deer are also implicated in disturbances promoting invasive species. This is all in addition to the considerable monetary impact that high deer populations have in destroying landscaping in resident’s yards and generating more numerous deer-car collisions, to say nothing of potentially entrenching Lyme disease in our area.

The Nature Conservancy observed:

In our opinion, no other threat to forested habitats is greater at this point in time — not lack of fire, not habitat conversion, not climate change. Only invasive exotic insects and disease have been comparable in magnitude. We can argue about which threat is more significant than another, but no one who walks the eastern forests today can deny the impact of deer to forest condition.

National environmental organizations have recognized the threat, and local field observations back it up. Deer overpopulation is a threat to the ecological health of our natural areas.

This should not be a surprise to us. Deer co-evolved with predators. We have increased deer habitat (more on that below) while also eliminating natural predators. A population explosion is too be expected. When this first came up I joked about bringing back wolves, but while deer thrive in a residential or office park-type ecosystem, wolves do not.

Therefore, we are in a situation where to do nothing is to choose one species over others. To do nothing is to prioritize the lives of deer over the lives of native trillium, which have been almost entirely eliminated from our nature areas. To do nothing is to prioritize the lives of deer over the oak seedling necessary for the regeneration of our forests, and to prioritize the lives of deer over the lives of other animals that will depend on the acorns and habitat that the mature oaks would provide. To do nothing is to prioritize the lives of deer over the lives of other animal species, such as the indigo bunting, which needs understory-level nesting habitat that is eliminated by deer.

All of our choices in this affect the web of life.

-How to deal with the problem:

Believing as I do that there is a problem, the next question is “what to do about it?”

Option 1–Do nothing: Not taking steps to address the impacts on natural areas is a problem, though it would be one I am loathe to accept, but if the costs of management were too high, I might have to resign myself to the natural areas destruction from an excessive deer herd. (Strategies that have been discussed to address landscape damage or car/deer collisions such as fencing and planting deer-resistant species do not address the natural areas impacts).

Option 2—Deer Fertility Control: The Humane Society of the United States has supported the experimental use of deer fertility control methods such as immunocontraception or surgical sterilization of does.

Many other communities have tried these approaches (see for example the Cornell efforts). Some areas have seen some level of success with this approach when the herd is confined such as one found on an island. Despite many times it has been tried in free-ranging herds (such as the one here), I have found no evidence that it successfully lowers the deer population.

That said, I think there may be potential in using non-lethal methods to manage the size of the deer herd after it is brought down to an appropriate level. This is not a sure thing, the main drug used in immunocontraception is not legal in Michigan for this use and may actually make does into “buck magnets” by having them go through estrus but not become impregnated. The other main approach, surgical sterilization, is a costly endeavor (around $1,000/doe) and has its own set of ethical concerns.

Still, I supported efforts to explore these options. For my part, I would be willing to spend more money on fertility control efforts to maintain herd size (though not unlimited amounts more) if there is either strong evidence of their success in that role or an appropriately-designed research methodology that would evaluate impact while protecting the ecology of our natural areas.

Option 3—culling: The third option, a cull with professionally-trained sharpshooter under highly-regulated conditions outside of the hunting season, is the option that I joined the majority on Council in supporting to reduce the herd size.

Obviously, this brings with it many concerns. Some are opposed to any lethal deer management efforts, others are concerned about the use of firearms in the City. I get it. I work hard in my day job to help move forward common-sense gun regulations to prevent gun death and violence. I used to be a vegetarian (yes, I know I lose credibility in that statement with the “used to be.”)

That said, when I look at the evidence I see a deer cull as the most effective effort to protect our natural ecosystems, and the success of culls across the country supports this position. Culls also have an excellent safety record, and reducing the deer herd size will bring with it increased safety for motorists.

Development does not decrease deer habitat

In the debate, several have argued that we have created this problem by destroying deer habitat to make way for development. While development does play a role here, it is actually the opposite. Deer need both open areas for browsing and forested areas for cover. They do not thrive in habitat this is all forest or all open field. So, residential and office park-style development actually increase deer habitat. According to an article in the New York Times:

Then suburbanization created a browser’s paradise: a vast patchwork of well-watered, fertilizer-fattened plantings to feed on and vest-pocket forests to hide in, with hunters banished to more distant woods.