Deer Management

Miami University Natural Areas (MUNA) encompass about 1,000 acres, forming a treasured green belt around much of the Oxford campus.  The Natural Areas were designated by President Paul Pearson in 1992 “to be preserved and protected for approved uses in education, research, recreation, and observation…in perpetuity.”  He was “confident 100 years from now [it] will be regarded as one of the most important events to occur in Oxford’s history.”  Indeed, the area is used in recruitment, research, and recreation.  However, its ecological integrity, biological diversity, and beauty have been degraded and are further threatened by invasive species and overabundant white-tailed deer.  While a comprehensive program to improve MUNA’s ecosystem health is planned, the overabundance of deer is an acute and increasing threat to tree and wildflower regeneration and requires a more rapid response.

Doe and fawns on campus at nightWhy is a deer management program needed?

Miami faculty and students have been studying the impact of deer in the Natural Areas since 2010, and the evidence is conclusive that the increasing deer herd is damaging the ecosystem of the campus greenbelt.  

The City of Oxford, Hueston Woods State Park, Cincinnati Parks, Great Parks of Hamilton County have established deer management programs in recent years because of similar concerns.  Universities, including Binghamton University, Swarthmore College, and Vassar College, have also launched such programs.

How many deer are there in the Natural Areas?

It depends on the specific area surveyed, but a 2018 master’s thesis recorded more than 18 deer per square kilometer (a square kilometer is about 250 acres) in the Bachelor Reserve, located off of Oxford-Milford Road.¹ Deer densities greater than 8 per square kilometer can cause severe negative impacts on the native ecosystem, nearby homes and farms, and even car insurance rates.

Tree trunk with bark scraped off from buck scraping antlersTree with what appears to be a dried out trunk, old scrapings on the side from a male deer's antlersWhat are the impacts of too many deer?  

It is well documented nationwide that excessive deer browsing – consumption of twigs, leaves and young trees - severely limits the ability of a forest to regenerate. When large trees die, smaller trees usually take their place in the canopy, but because of deer browsing on saplings there are fewer young trees to fill in the canopy. Because deer are selective in the browsing, elevated populations can damage or eliminate plant species, which then negatively impacts the diversity and abundance of animal species and, ultimately, how the forest functions.

Wildflower populations and native shrubs are also being reduced by overabundant deer.² Ongoing research by Miami faculty and students involving deer exclosures (66 by 66 feet fenced areas to keep deer out) show that deer are the major cause of reduced biodiversity in the Natural Areas with invasive bush honeysuckle a secondary cause. Tree seedlings and saplings, essential for regeneration of any forest, are increasingly sparse in non-fenced areas.³ Deer are also browsing on local gardens and crops, causing deer-vehicle collisions, and damaging trees and other horticultural plantings on campus. Deer often elevate tick populations, raising concerns about tick-borne diseases that impact people, pets, and livestock. In the long term, reduced regrowth of canopy trees may reduce the carbon sequestration in forests.

What is being considered to reduce deer impacts in Miami’s Natural Areas?

The Miami University Natural Areas Committee (NAC) has convened a committee to assess the impacts of deer, explore solutions, and draft a deer management plan. This committee includes Miami faculty and staff, as well as representatives from the student body, the City of Oxford, and community members. 

An initial draft of that plan will be posted here and shared with the broader University and Oxford communities. We will seek feedback and input from community members, take this feedback and inputs into consideration, and make revisions to the plan. The final plan will be considered by NAC and, if recommended, by the Miami University administration.

After considering different options to reduce local deer populations, the option that appears to best suit conditions in the MUNA is bow hunting, limited to specific areas, by vetted individuals. More details will be included in the draft plan.

A doe near one of the Natural Areas pathsIf we reduce the deer population in the Natural Areas, won't more deer come in from other places?

Female and young deer are not likely to move in quickly, because does have fairly small home ranges that they rarely leave and the deer already present will have some deterrent effect. But, over time, deer numbers will increase, due to births and to deer moving in from nearby areas. Land management, including the management of herbivores, is an ongoing process, especially when natural predators are no longer present. Because deer are also being managed on adjacent and nearby City of Oxford land and some private lands, management in the MUNA will contribute to reducing deer density and improving forest ecosystem health over the larger landscape.

How will the success or failure of the deer management program be evaluated? 

The ongoing long-term research by Miami faculty and students will continue with sapling regeneration and deer density to determine the impact of the deer management program. This information will be publicly available. We also look forward to a day when the natural abundance of wildflowers like trillium and bluebells is restored. In spring, blankets of wildflowers and an absence of the browse-line (a hedge-like line of leaves, below which the forest is stripped bare of leaves) will be evidence that our local ecosystem is regaining balance.

If it’s a natural area why not leave it to nature and take a hands-off approach?

Humans have caused the conditions leading to deer over-population, including predator extermination and landscape changes that have increased the amount of edge habitat and food supply. The impact of too many deer is devastating to forest plant and animal species. If we do nothing, we will lose much of what we value in our campus greenbelt.

How can I learn more about deer impacts in Miami’s Natural Areas?

Reports on deer management options, and the City of Oxford’s plan, are in Footnote 4.


Footnote 1

Table 2 from Peterson (2018) MS thesis, reporting estimated deer density in Miami University Natural Areas (MU) and sites in Hueston Woods State Park (HW). Note that field work was done in 2017. There are 2.6 km2 per square mile, so 13.6 deer per km2 is 35 deer per square mile.

Estimated white-tailed deer densities in the eight locations sampled within Miami University's Natural Areas (MU) and Hueston Woods State Park (HW).
Site Location Spring Estimated Density (deer km2) Summer Estimated Density (deer km2) Net Change (deer km2)
1 Kramer Preserve (MU) 6.0 4.2 -1.8
2 Reinhart Preserve (MU) 7.9 7.8 -0.1
3 Bachelor Preserve 18.2 9.5 -8.7
4 Western Woods (MU) 13.6 8.8 -4.8
5 College Woods (MU) 8.0 5.0 -3.0
6 Cemetery (HW) 4.8 3.3 -1.5
7 Horse Trail (HW) 7.0 6.4 -0.6
8 Big Woods (HW) 0 0 0

Horsley et al. (2003) found that deer densities greater than 8/km² caused dramatic shifts in vegetation. There are 2.6 km² per square mile, so 8 deer per km² is 21 deer per square mile.

Horsley SB, Stout SL & deCalesta DS (2003) White-tailed deer impact on the vegetation dynamics of a northern hardwood forest. Ecological Applications, 13, 98–118.

Peterson TE. 2018. Factors affecting densities of white-tailed deer (Odocoileus virginianus) in eastern deciduous forest: the roles of and surrounding land use, forest habitat edge, and invasive shrubs [master’s thesis]. Oxford (OH): Miami University.

Footnote 2

Averill KM, Mortensen DA, Smithwick EAH, Kalisz S, McShea WJ, Bourg NA, Parker JD, Royo AA, Abrams MD, Apsley DK, Blossey B, Boucher DH, Caraher KL, DiTommaso A, Johnson SE, Masson R, & Nuzzo VA (2018) A regional assessment of white-tailed deer effects on plant invasion. AoB PLANTS 10:plx047

Kelly JF 2019. Regional Changes to Forest Understories Since the Mid-Twentieth Century: Effects of overabundant deer and other factors in northern New Jersey. Forest Ecology and Management  444: 151-162

Footnote 3

Haffey CM & Gorchov DL (2019). The effects of deer and an invasive shrub, Lonicera maackii, on forest understory plant composition. Ecoscience, 26(3), 237-247.

Species richness and stem density of tree seedlings (30-200 cm height) in 2015 were both lower where deer had access than in deer exclosures; neither measure was affected by honeysuckle treatment (Haffey and Gorchov 2019). The density of tree seedlings in the deer access plots averaged 0.034 per m², compared to 0.195/m² in deer exclosures (Haffey and Gorchov, unpublished). For comparison, seedling densities in forest sites in New Jersey 1948-1973, before the recent increases in deer density, averaged 0.75/m² (Kelly 2019), indicating that even after 5 years of deer exclosure, tree seedlings were sparse compared to normal forests.  Across all plots (deer access and exclosure), the density of saplings (2.5 – 5 cm diameter at breast height) averaged 0.025/m², much lower than range of 0.07 to 0.13/m² for a range of forests in Illinois (Sucheki and Gibson 2008).  

Sucheki PF & Gibson DJ (2008) Loss of Cornus florida L. leads to significant changes in the seedling and sapling strata in an eastern deciduous forest. Journal of the Torrey Botanical Society 135: 506-515.

Footnote 4: Relevant reports on deer management options