Solon resources addressing deer management
What does “we have a deer problem” mean? How does Cleveland Metroparks determine the number of deer in each reservation? Is birth control available for deer populations?
The “deer problem” is an indication that the local biological system is out of balance. In nature, all biological communities, or ecosystems, are in a state of flux. At the same time, balances evolve among all the components of the system, including the non-living (soil, water, etc.) and the living components (plants, animals). A “deer problem” exists when the number of deer exceeds the ability of the environment to support the deer. The “deer problem” also refers to human interaction with deer, such as landscape damage, farm damage, automobile/deer accidents, and concerns for disease transmission. An environmental balance is of primary concern to Cleveland Metroparks, but as a member of the larger community of Northeast Ohio, other issues cannot be ignored.
What caused the “deer problem” to occur?
Deer were over-hunted in Ohio and disappeared from the landscape by 1900. The rapid growth in the deer herd size in Northeast Ohio is directly related to several factors. Natural predators of deer are absent from today’s environment. Mountain lions, wolves, black bear, and indigenous people were the primary factors affecting deer population in pre-settlement times. Human influences have caused changes to the land over the past 150 years. Vegetation cover has been transformed from primarily mature forests to present-day urban and quasi-rural landscapes with well-developed residential communities. Deer have successfully found food in these new environments which spurred high reproductive success and survivorship. With no natural predators to control population growth, continuing urban expansion, local ordinances prohibiting hunting, absence of disease and adaptive food habits, deer populations have increased markedly. Deer density, (commonly referenced as number of deer per square-mile) has intensified accordingly.
Deer social groups (matriarchal does & yearling social groups / male “bachelor” groups outside the mating season) form home ranges that vary according to local deer density, landscape, travel corridors and foraging habits. These home ranges presently shift very little. Food availability and food preferences within these static home ranges have been sustained by the adaptive nature of white-tailed deer. As a result, deer feeding or “browsing” habits in Cleveland Metroparks have shifted from open edges and understory plant sources to interior forest vegetation consisting of native forest floor plant and understory tree species.
What are the principal impacts of the “deer problem” to Cleveland Metroparks?
Cleveland Metroparks is charged with conservation of natural resources as its fundamental mission. The impacts of large deer populations became evident in portions of the reservations by the late 1980’s. The most noticeable impacts are to the plant life at ground and mid-understory levels (what the deer can reach while foraging) and to the other wildlife species that depend upon these disappearing resources.
“Browse lines” develop in areas with too many deer. Spring plants, especially the typically abundant forest wildflowers, are especially hard hit as they are the first new growth after the long winter. As these plants are repeatedly browsed, they are unable to reproduce and often die out because their nutrient-energy reserve is depleted without the ability to go through a normal seasonal growth cycle. Seedling trees are heavily browsed by deer, often to the point where forest regeneration stops. Plants that are not preferred by deer expand, including grass, some sedge, and many unwanted exotic (non-native) species.
The cumulative effect on natural areas, especially forested areas, is so great it devastates the ecosystem. The forest communities will take many years to recover. Some areas have been impacted by deer browsing to such a severe degree that reproduction of new forest trees has essentially stopped. In these areas, native plants, like annual wildflowers, may need to be re-introduced. Neo-tropical migrating and year-round songbirds are dependent upon groundcover and the shrub/tree understory that provide nesting and foraging cover. These species are challenged to find nesting opportunities in Cleveland Metroparks forest areas that lack understory and groundcover habitat decimated by deer browsing. It is the goal of the Cleveland Metroparks to ensure successful native forest regeneration and native plant species growth by reducing deer population/density to the level where forest health indicates successful balance has been achieved.
Why doesn’t nature “take its course” and reduce the deer population through natural means?
The effects of a lack of natural predators to maintain population growth, urban expansion, local ordinances prohibiting hunting, absence of disease, the adaptive food habits of deer and backyard deer feeding stations, all combine to encourage very high populations of deer. High populations may be able to persist for a long time, absent a disease epidemic like chronic wasting disease. In short, letting nature “take its course” and allowing deer populations to increase without any control have significantly impacted plant and other animal species.
How long has Cleveland Metroparks been studying the problem and what type of field research is done?
Cleveland Metroparks Natural Resources staff have been studying and monitoring the deer population in the Park District since the early 1980s. Field surveys demonstrated a rapid decline in interior forest plant communities resulting from increased deer densities at the local landscape level by the late 1980’s. After exploring practical options for reducing deer populations, culling was chosen. Culling areas within the Cleveland Metroparks were identified from deer density level and browse impact survey data. Culling began in 1998. Field surveys and research consist of, but are not limited to:
Cleveland Metroparks uses a number of annual field surveys to monitor deer populations. One technique is using infrared videography from a fixed-winged airplane to provide estimates of deer numbers and determine locations of deer social groups. Other field surveys to monitor deer populations include spotlight counts, deer pellet (scat) counts, mapping home ranges of deer social groups, tracking deer, and counting deer that use bait stations. Research indicates that the density level in a balanced system would be between 10 and 20 deer per square mile. However, the key issue should not be looked at as “how many deer is the right number?” but, rather, monitoring the environment’s response to the deer population and reducing the number until the environment indicates the “right” number of deer.
How will the environment tell us when we have the “right” number of deer?
By using research which:
Cleveland Metroparks has seriously investigated alternatives to the current deer management program. From 2001 to 2006 nearly $500,000 was spent to investigate the efficacy of immunocontraception as an alternative means of controlling deer populations. Cleveland Metroparks concluded, as have other recent studies, that immunocontraception did result in decreased pregnancies. However, the free-ranging nature of the deer herd in the region where both immigration and emigration take place make it difficult to deliver the contraceptive to a large number of deer. Studies are being followed in other states that are testing immuno-contraceptive vaccines based on porcine zona pellucida (PZP) and gonadotropin releasing hormone (GnRH) (SpayVac™ and GonaCon™) and more effective delivery methods. Currently, immunocontraceptives (or other contraception agents) may only be used legally for research and not management purposes on wild deer populations in Ohio. This use must be authorized by federal regulatory agencies and the Ohio Division of Wildlife. Currently, the Ohio Division of Wildlife is not allowing use of immunocontraceptives for deer population management.
Is it true that if you reduce the deer herd they will have triplets, causing a “rebound effect?”
This does not occur with deer management programs. Deer reproduction, monitored by Cleveland Metroparks since 1998, has averaged approximately 1.7 fawns per yearling and older does throughout the management period. Twins are the norm with 68% of does bearing twins, 23% having single births, and approximately 4.5% bearing triplets. 4.5% of yearlings or older have not produced fawns.
How are deer culled in Cleveland Metroparks?
Under permits granted by the Ohio Division of Wildlife, sharp-shooting is used to reduce deer populations. Experienced and trained teams of Cleveland Metroparks employees implement the annual program. All personnel directly involved are law enforcement employees (Rangers) who have been tested for firearm proficiency. Specific reservations are closed to the public during deer management activities, and Rangers are stationed at the entrances of each reservation at the time management activities are being conducted to insure the safety of park visitors. The majority of the effort is concentrated during the time period when deer are most active (near dawn and dusk.)
All shots are taken from elevated platforms, either truck-mounted or tree stands to ensure safety. Animals are taken in areas of known concentrations and/or in areas that have been baited previously. Most culling areas are open grass areas, road berms, managed meadows and early successional old fields to allow for open shots. This insures the humane and safe culling of deer.
Additional Cleveland Metroparks staff assists with field dressing, transporting meat to the processor and servicing equipment. All animals are field dressed the same night and delivered to the processor the next day. Based on pre-arranged schedules, processed meat is donated to hunger centers including the Cleveland Food Bank. Since the inception of the management program more than 60,000 pounds of meat has been donated to feed the hungry.
How does Cleveland Metroparks determine the number of deer in each reservation?
Is birth control available for deer populations?