White-Tailed Deer: Grim Reaper of the Deciduous

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White-Tailed Deer: Grim Reaper of the Deciduous Forest
Perhaps no animal in Pennsylvania can bring about more controversy or generate more
emotional attachment than the white-tailed deer, Odocoileus virginianus. The white tail can be
found in a variety of habitats that includes farmland, suburbs, and forests; it is even capable of
surviving in urban patches of green (“Deer hunt comes,” 2011).
The whitetail’s range extends from southern Canada to northern South America and most of the
United States; it is absent in the southwestern U.S. (Fergus, 2000). The history of the whitetail in
Pennsylvania mirrors that which happened in other areas. Once abundant, overhunting, combined
with deforestation resulting from the change in land use to agriculture and its accompanying
habitat degradation, nearly drove the while tail into extinction by the mid-1800’s.
The alarming drop was the impetus for the creation of the Pennsylvania Game Commission in
1895. The organization quickly established bag limits for the white tail for the purpose of
allowing the animal to recover its population. Since that time, white tail populations have
climbed, aided by the elimination of natural predators and the improvement in habitat quality
created when abandoned farmland gave rise to secondary growth forest (Cote et al., as cited by
Morissette, Lavoie, & Huot, 2009) consisting of even-aged economically valuable species such
as white ash, as white ash, sugar maple, red maple and black cherry (McClenahen & Hutnik, as
cited by Stromayer & Warren, 1997).
Although no one is certain of the deer population of pre-Columbian times, today’s estimated 25
to 27 million individuals may exceed the pre-Columbian numbers (Shedd, 2000). This may be
partially due to the whitetail’s biology; female deer have a remarkable ability to respond to
decreases in habitat quality; a reduction in food availability resulted in smaller female deer who
maintained their reproductive rate. It was only when a drastic reduction in vegetation quality
occurred before a corresponding decrease in density occurred (Anouk-Simard, Cote, Weladji, &
Huot, 2008).
The whitetail eats between five and nine pounds of food daily, feeding on plant material such as
tree bark, twigs, lichens, wildflowers, grasses, garden vegetables, acorns, and ornamental plants
(Fergus, 2000). The white tail’s propensity for eating is the root of the problem. Considered by
many to be a keystone herbivore (“White-tailed deer management plan,” 2006), they are capable
of upsetting otherwise stable ecosystems with densities as little as ten individuals per square mile
(deCalesta, as cited by “White-tailed deer management plan,” 2006). Browsing pressure exerted
by the Pennsylvania’s state mammal is threatening the future of Penn’s Woods; Pennsylvania’s
high quality mixed hardwood forests are giving way to regenerated stands made up of red maple,
black birch, and other less economically viable valuable trees (Shedd, 2000).
Hunting is one method of keeping the white tailed deer population in check; Pennsylvania
hunters take 350,000 to 400,000 deer annually of the estimated 1.4 million that reside within the
state (Fergus, 2000). In 2002, the Pennsylvania Game Commission responded to the deer
overpopulation crisis by altering the hunting seasons so that the doe season now occurs prior to
the antlered season, allowing females to be culled prior to breeding (“QDMA,” 2010). This
allows antlered males to remain in the population, resulting in healthier deer herds since the
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stronger males are doing the breeding, rather than smaller males who survived antler season
(Shedd, 2000).
Today, despite the successful game laws and initiation of doe seasons, the southeastern part of
Pennsylvania is crippled by a deer population that has grown beyond carrying capacity. In an
area where few people are traditional hunters and where hunting in densely populated areas is
difficult and unsafe, alternative methods of controlling the white tail need to be examined. This
is not without controversy, however. The anthropomorphizing of the white tailed deer, depicted
in the Walt Disney film Bambi, has led to misunderstanding of the role of hunting in curtailing
populations of this ecologically destructive mammal. Commonly referred to as the Bambi
Syndrome (Cartmill, 1993), people in the suburbs do not always support or understand the need
for culling the population (Decker & Gavin, 1997).
White-Tailed Deer Impact on Vegetation
There have been numerous studies attesting to the negative impact that white tailed-deer have on
vegetation and on ecosystem functioning. A common method of evaluating the whitetail’s
impact on an ecosystem is through the utilization of deer exclosures; fenced off plots that
scientists compare to unfenced plots to fenced plots (Martin, 2006). Exclosure fences have also
been used to measure the impact of deer on agriculture; exclosures result in greater masses of
high-quality corn produced than in unfenced plots (Stewart, Mcshea, & Piccolo, 2007).
The role of white-tailed deer as a keystone species of eastern United States forests (“White-tailed
deer management plan,” 2006; Holmes, Curran, & Hall, 2008) is creating alterations in tree
density, regeneration, and species composition (Stromayer & Warren, 1997) in a variety of forest
types (Royo, Stout, deCalesta, & Pierson, 2010). In the New Jersey pine region, over-browsing is
eliminating the Atlantic white cedar (Stromayer & Warren, 1997), a relatively stable tree species
that has survived centuries of natural disasters and harvesting, while old growth fir stands are
being replaced by spruce trees (Morissette, Lavoie, & Huot, 2009). In riparian areas, regenerative
growth is substantially reduced by deer grazing (Opperman & Merenlender, 2000), setting the
stage for colonization of invasive species, while studies show that over-browsing within rare
maritime holly forests, characterized by the American holly, leads to a change in species
composition in which the American holly is replaced by stands of black cherry (Forrester,
Leopold, & Underwood, 2006).
This alteration is brought about when deer consume nearly all small saplings and vegetation
below six feet, leaving a distinctive “browse line” in their wake, which marks the height of
vegetation that deer can reach when on their hind legs (“Deer facts,” 2012). The end result is a
forest floor devoid of ground cover that deer find palatable. As mature trees die and light gaps
open, seedlings of light-tolerant species sprout up, effectively creating an altered state ecosystem
(Holmes et al., 2008).
Over-browsing of ground cover results in extirpation of sensitive forbs, such as species like
Solomon’s Seal (Fletcher et al., as cited by Forrester et al., 2006), and others from the Trillium
genus (Augustine & Frelich, 1998). Results of deer exclosure studies indicate that such forbs are
slow to recover from over-browsing, often resulting in little or no regeneration (Forrester et al.,
2006).
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Impact on Other Organisms
Over-browsing extends beyond tree composition, however, at the expense of other wildlife who
depend upon native vegetation (Rossell, Patch, & Salmons, 2007). Nesting birds, for example,
are negatively impacted by the removal of critical ground cover (Sterba, 2005). A decline of
intermediate canopy-nesting songbirds has been linked to high deer densities with the threshold
deer density number existing between 7.9 and 14.9 deer per square kilometer (deCalesta, 1994).
Over-browsing also causes shifts in bird species in response to changing vegetation; these shifts
are reversible with decreases in deer density (McShea & Rappole, 2000). Deer densities of 20 to
38 deer per square mile have been found to be the threshold for which deer negatively impact
forest bird communities within northeastern Pennsylvania (“White-tailed deer management
plan,” 2006).
Forest Response to Deer Removal
Reductions in deer population have mixed results on vegetation regeneration. The synergistic
effects of over-browsing, habitat fragmentation, and invasive species are altering the landscape,
creating forests consisting primarily of vegetation unpalatable to deer (Holmes et al., 2008). The
remaining disturbance-tolerant species, such as the pawpaw (Asimina triloba), American beech
(Fagiis grantifolia), and jewelweed (Impatiends capensis), may act to prevent growth of browsesensitive species (Scholl, 2004). Over-browsing is also negatively impacting economically
important hardwood species upon which the Pennsylvania timber industry depends are being
negatively impacted (McClenahen & Hutnik, as cited by Stromayer, & Warren, 1997).
Many studies have concluded that over-browsing by white-tailed deer has resulted in an
alternative stable ecosystem that replaces the normal succession usually observed in eastern
United States deciduous forests (Stromayer & Warren, 1997), and results in recruitment failure
when over-browsing occurs after clear cutting or some other canopy disturbance (Tremblay,
Huot, & Potvin, 2007). The altered state is evidence of a system whose normal checks and
balances are not functioning properly (Caughley, as cited by Stromayer & Warren, 1997). An
alarming pattern present in the literature is that despite deer removal, many forests fail to
regenerate as expected. Although ground cover increases following white tailed deer removal,
recovery is limited to browse-tolerant species and diversity remained lower than expected
(Forrester et al., 2006). Reversal of this trend will only be possible through careful management
reforestation of native trees (Holmes et al., 2007).
Maintaining a mixed forest whose composition includes oak trees is vital for biodiversity;
numerous organisms such as the black bear, mice, and birds rely on its acorns (Roberson, 2007).
Although he decline of the economically-important oak is not due to over consumption of acorns
by deer (Haas & Heske, 2005), but rather to over-browsing of young oak saplings, a reduction in
oak trees will mean fewer acorns, a staple crop of numerous birds as well as the black bear, who
depend on the acorns fat to get them through the winter (Roberson, 2007).
Deer in the Suburbs
Without predation, hunting, or seasonal malnutrition (Piccolo, 2010) to keep deer populations in
check, over-browsing by whitetails has spilled into suburban backyards of the northeastern
United States. Excess deer numbers in suburban areas result in deer damage that includes
destruction of ornamental plants, vehicular collisions involving deer (Green, Askins, & West,
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1997), and increased rates of Lyme disease (“Reduce deer population,” 2004). Suburban deer
populations pose a difficult challenge for wildlife managers (Hanback & Blumig, 1993) since
traditional approaches to managing deer, such as recreational hunting, are often rejected by
suburbanites who enjoy seeing deer in their neighborhood (Decker, & Gavin, 1987; Campbell,
Laseter, Ford, Miller, & Euler 2004).
Valley Forge National Park
The detrimental effect of a whitetail population existing beyond its carrying capacity can be
easily witnessed at Valley Forge National Park. Valley Forge, home to the Continental Army and
George Washington during the winter of 1977-1778, consists of 3500 acres situated in
Montgomery County, Pennsylvania; an affluent and densely populated suburb of Philadelphia.
Although its main mission is to protect a historical area and to educate the public regarding the
area’s history, the size of Valley Forge National Park makes it a significant island for
biodiversity within an otherwise overly developed and fragmented area (“Valley Forge,” 2007;
“Animals,” 2006).
A glance at the wood line at Valley Forge reveals the distinctive browse line created by overbrowsing. This line first became apparent in the mid-1990s and coincides with increasing reports
of Lyme disease (“White-tailed deer management plan,” 2006). Previous to that, a deer study
conducted in 1983 revealed a population of approximately 165-185 animals; a population that
was within its carrying capacity as indicated by the excellent habitat condition (Leong & Decker,
2007). Over the last two decades, however, the population has swelled (Lovallo & Tzilkowski, as
cited by “White-tailed deer,” 2006). The deer at VFNP present a unique management challenge;
hunting is not allowed at national parks, and the deer contained within are managed by the
National Park Service rather than the Pennsylvania Game Commission.
In response to the need to obtain an accurate estimate of the park’s white-tail deer population and
understand their movements, 105 deer were involved in a mark and recapture study which
utilized radio telemetry starting in 1997 (“White-tailed deer management plan,” 2006).
Understanding deer movement informed park officials about habitat use and effectiveness of
proposed management techniques. Findings indicated that 88% of the females stayed within 400
feet of the park boundary and limited their home range to .46 square miles (“White-tailed deer
management plan,” 2006).
Beginning in 1992, the effect of browsing on long-term vegetation was monitored using (30) 2
meter by 2 meter randomly fenced plots partnered with unfenced plots. Data was collected
during four different years over a decade beginning with the year 1993. Findings indicated that
unfenced areas contain primarily browse-resistant plants and non-native species, while fenced
plots yielded three times the tree seedling density as unfenced plots. Red oak seedlings survived
only within fenced areas, and no seedlings of any species between 20 and 59 inches were found
in the unfenced plots (Heister et al., as cited by “White-tailed deer management plan,” 2006).
The conclusion was that browsing will prevent forest regeneration and decrease habitat quality
for lower canopy and ground nesting birds (“White-tailed deer management plan,” 2006). Based
on this information, park biologists made the decision to reduce deer numbers within the park,
ultimately deciding to employ federal sharp shooters to cull the herd in order to allow adequate
tree regeneration of 8,079 seedlings per acre (“Briefing statement,” 2009).
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VFNP is currently in the second year of a four year lethal reduction phase in which the goal is to
reduce the deer population from an estimated 241 deer per square mile (approximately 1277
deer) to somewhere between 31 and 35 deer square mile. This will bring deer numbers to the165185 range; the same number of deer that existed in the park in 1983. Numbers will be reduced
through a combination of sharpshooting and capture and euthanasia. Last fall, federal
sharpshooters using night vision goggles and high-powered rifles to reduce the deer population
by 600; over 18,000 pounds of meat were donated to local shelters. A further reduction of an
additional 500 deer is planned for the winter of 2011-12 (“Valley Forge Park officials call,”
2011). Park managers plan to keep the deer within the target range using female birth control if
an acceptable one becomes available once four years of lethal control have occurred (“White
tailed deer management,” 2006).
Employing lethal methods to decrease deer populations is one that has been practiced in other
national parks. In 1995, Gettysburg National Military Park decided to use federal sharpshooters
to cull deer whose voracious appetite for crops and woods were destroying the historical aura
recreated within the park (O’Connell, 1995), although culling was halted for 18 months when an
injunction was filed by animal rights activists (Kratzke, 2011). The Grand Teton National Park
and other places have resulted in similar controversial hunts involving elk populations whose
numbers had outgrown carrying capacity (“National Park Service strives,” 2011).
PUBLIC OPINION
Arriving at the decision to cull the herd via sharpshooters was not easy given the demographics
of the surrounding area since suburbanites are often unfamiliar with hunting or the role that it
plays in keeping deer populations in check, and typically prefer non-lethal methods such as
transportation and contraceptives (Green, et al., 1997). Viewpoints represented by animal rights
groups can make management issues a challenge, and therefore many park managers are fearful
of lawsuits (Leong & Decker, as cited by Stewart et al., 2007).
Since careful facilitation in which stakeholders are involved is crucial to the process (Shedd,
2000), prior to making the decision to use lethal methods, interviews were held to determine the
public opinion regarding the deer situation. Interviewees consistently expressed a positive
response to viewing deer within the park (Leong & Decker, 2007). Of those interviewed, known
stakeholders understood the complexities of deer management issues best; other interviewees
were frequently of the opinion that deer did not need to be managed (“White-tailed deer
management plan,” 2006).
In accordance with the National Environmental Policy Act, park officials prepared an
Environmental Impact Statement and outlined four scenarios for controlling the deer population
(Kozlowski, 2011). Park officials involved the public extensively through the use of a website,
brochures, public meetings, and numerous briefings to local organizations (“Briefing statement,”
2009). Ultimately, it was decided to target the deer population to 31 to 35 per square mile, a
number that can be adjusted given the rate of forest regeneration (“Briefing statement,” 2009).
The plan is to initially decrease the population over a period of four years, and then use
reproductive control if an acceptable one becomes available; lack of an effective contraceptive
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would mean that lethal control would continue to occur (“Briefing statement,” 2009). The
decision to use lethal methods was one of cost-effectiveness (Stewart, 2007), as other
alternatives examined proved too expensive or inefficient.
Despite the effort to involve the public, the citizen group CARE, Compassion for Animals
(“Care is fighting,” 2009), attempted to halt the deer reduction plan, refuting its effectiveness and
claiming that the park’s coyote population was capable of keeping the deer under control, a
sentiment was not backed by park officials (“Briefing statement,” 2009).
Alternatives
Park officials examined a number several management including translocation of the animals,
fencing the park, sterilizing the male deer, fencing the entire park, hazing the deer from the park,
public hunting, supplemental feeding, translocation, predator reintroduction, the use of
repellants, and poisons. The options were rejected on the basis of ineffectiveness, cost, human
safety, or difficulty (“White-tailed deer management plan,” 2006).
Other alternatives were seriously examined prior to the decision to use lethal methods. The first
was to take no action and allow predators to maintain the population. This was ultimately
rejected because studies indicate that coyotes are ineffective at effectively controlling deer
(Kozlowski, 2011).
Since immunocontraception is the most widely used non-lethal population control method and
has the best potential for use in urban environments (Blumstein, 2011), the use of contraceptives
was also critically examined as studies have shown that the whitetail’s high site fidelity make it a
viable method of population control because immigration is unlikely to increase local
populations. Furthermore, habituated deer, such as the deer at VFNP, are relatively easy to dart.
Ultimately, the use of contraceptives was rejected due to difficulties such as distinguishing
treated and untreated females, the necessity of treating deer one year with follow-up treatment
the next year and the difficulty in developing a viable delivery method since contraceptive-laced
baits can be harmful to other wildlife or even to humans who consume deer who have fed upon
contraceptive bait (Rutberg et al., 2004; Hanback & Blumig, 1993). Educating the public
regarding the issues associated with contraceptives is important; the public often does not
understand the cost of this method or the difficulties of effective application (Green, 1997).
A third option examined was to fence the park; this option would not address issues with overbrowsing and was rejected due to the high cost associated with installing, monitoring, and
maintaining an 8 feet fence for the 3500 acre park (Blumstein, 2011). Additionally, public access
to the park would be impacted and fencing would destroy to historical image that the park
projects (Blumstein, 2011).
The Role of Education
People in the suburbs often view deer as valued wildlife, often choosing to feed deer which is a
problem for a number of reasons (McCullough; McNay; as cited by Leong, & Decker, 2007).
Deer quickly become habituated and the carrying capacity artificially increases, leading to
habitat degradation (Green et al., 1997). Although the deer at VFNP were not fed by local people
(Leong, & Decker, 2007), educating people about the issues with feeding deer is an important
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role in keeping deer populations in check. It is currently legal to feed deer in PA up to 30 days
prior to hunting season, although the Game Commission discourages it (“Please don’t feed the
deer,” n.d.) Many residents do not realize the harm they are doing by feeding deer (Chunko,
2010) or that they could cause a deer’s death through acidosis, a condition in which the pH level
falls dramatically and the animal dies of shock shortly after consuming corn (“PGC wildlife
veterinarian,” 2012).
The use of lethal methods to control suburban deer populations is both controversial and political
due to animal rights groups who feel deer need protection (Girard; Curtis; Decker & Richmond,
as cited by Green et al., 1997). Since the public plays an important role in managing suburban
populations, education must play a role in order to garner support for lethal management
techniques (Decker & Gavin, 1987) and to inform the public about the costs and consequences of
deer management (Green et al., 1997). Part of the public outrage over the lethal management
techniques used at VFNP may be due to a lack of knowledge regarding management techniques.
Although the decision to use lethal methods to control deer on at VFNP was undertaken with
great angst, it is a decision that will surely be repeated in coming years as communities up and
down the eastern seaboard come to terms with the controlling the once-threatened and now
prolific whitetail in order to preserve deciduous forests for future generations.
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Tremblay, J., Huot, J., & Potvin, F. (2007). Density-related effects of deer browsing on the
regeneration dynamics of boreal forests. Journal of Applied Ecology, 44, 552-562.
doi:10.1111/j.1365-2664.2007.01290.x
U.S. Department of the Interior, National Park Service, Valley Forge National Park Service
(2009). Briefing statement. Retrieved from
http://www.nps.gov/vafo/parkmgmt/upload/VAFO_DEIS_BriefingStmt_2_27_09_final-2.pdf
U.S. Department of the Interior, National Park Service, Valley Forge National Park Service
(2006). White-tailed deer management plan / environmental impact statement final internal
scoping report. Retrieved from
10
http://www.nps.gov/vafo/parkmgmt/upload/Final%20Internal%20deer%20Scoping%20Report.p
df
Valley Forge National Historical Park Information & History. (2007). Retrieved from
http://www.valley.forge.national-park.com/info.htm
Valley Forge Park officials call deer cull a success. (2011, April 1). Mainline Media News.
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http://mainlinemedianews.com/articles/2011/04/01/main_line_suburban_life/news/doc4d94cf679
9f78001603652.txt
Appendix
Include pictures
11
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