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Browsing by overabundant herds of white-tailed deer (Odocoileus virginianus) can cause significant economic damage to agricultural crops and landscape plantings. In many instances, for both commercial growers and homeowners, commercially available repellents may be an appealing alternative to physical exclusion and lethal control of animals. We tested 10 different commercially-available repellents (Chew-Not®, Deer Off®, Deer-Away® Big Game Repellent, Plantskydd®, Bobbex®, Liquid Fence®, Deer Solution®, Hinder®, Repellex® systemic tablets, and coyote urine) on yews (Taxus cuspidata Densiformis) at 2 different locations in Connecticut. The study included both positive (fence) and negative (no treatment) controls. We planted yews in 2 blocks at each location in the spring of 2006; each block had 12 groups of 6 yews. We randomly assigned one of the 12 treatments to each group of yews within each block. We applied repellents based on manufacturers’ label recommendations for the 2006 and 2007 growing seasons and recorded application costs. We derived a protection index based on plant size and dry needle weights at the end of the 2007 growing season. In general, repellents that required more frequent application performed better. Bobbex® ranked highest, but was the most expensive repellent treatment. Hinder® performed nearly as well at a fraction of the cost. Yews protected by Repellex®, Deer Solution®, coyote urine, and Plantskydd® were the same size as unprotected controls at both sites and did not have significantly more needles. No repellents prevented 100% of browse damage. The choice of repellent usage is a trade-off among effectiveness, cost, ability to follow recommended reapplication interval, and plant to be protected.
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HumanWildlife Interactions 4(1):56–66, Spring 2010
Effectiveness of deer repellents
in Connecticut
JEFFREY S. WARD, Department of Forestry and Horticulture, Connecticut Agricultural Experiment
Station, P.O. Box 1106, 123 Huntington Street, New Haven, CT 06504-1106, USA jeffrey.ward@
ct.gov.
SCOTT C. WILLIAMS, Department of Forestry and Horticulture, Connecticut Agricultural Experi-
ment Station, P.O. Box 1106, 123 Huntington Street, New Haven, CT 06504-1106, USA
Abstract: Browsing by overabundant herds of white-tailed deer (Odocoileus virginianus) can
cause signi cant economic damage to agricultural crops and landscape plantings. In many
instances, for both commercial growers and homeowners, commercially available repellents
may be an appealing alternative to physical exclusion and lethal control of animals. We tested
10 different commercially-available repellents (Chew-Not®, Deer Off®, Deer-Away® Big Game
Repellent, Plantskydd®, Bobbex®, Liquid Fence®, Deer Solution®, Hinder®, Repellex®
systemic tablets, and coyote urine) on yews (Taxus cuspidata Densiformis) at 2 different
locations in Connecticut. The study included both positive (fence) and negative (no treatment)
controls. We planted yews in 2 blocks at each location in the spring of 2006; each block had
12 groups of 6 yews. We randomly assigned one of the 12 treatments to each group of yews
within each block. We applied repellents based on manufacturers’ label recommendations for
the 2006 and 2007 growing seasons and recorded application costs. We derived a protection
index based on plant size and dry needle weights at the end of the 2007 growing season.
In general, repellents that required more frequent application performed better. Bobbex®
ranked highest, but was the most expensive repellent treatment. Hinder® performed nearly
as well at a fraction of the cost. Yews protected by Repellex®, Deer Solution®, coyote urine,
and Plantskydd® were the same size as unprotected controls at both sites and did not have
signi cantly more needles. No repellents prevented 100% of browse damage. The choice
of repellent usage is a trade-off among effectiveness, cost, ability to follow recommended
reapplication interval, and plant to be protected.
Key words: conditioned aversion, Connecticut, human–wildlife con icts, Odocoileus
virginianus, repellent, Taxus cuspidata Densiformis, white-tailed deer, yew
White-tailed deer (Odocoileus virginianus)
populations in Connecticut have steadily
increased from an estimated <20 animals
in 1900 to an estimated >76,000 today. With
overabundant deer herds living in areas of
medium to high human density, con icts arise.
In many areas of high deer density, deer are no
longer considered an awe-inspiring, valuable
natural resource, but rather tra c hazards,
pests that damage landscape plantings and
agricultural crops, and important hosts of the
ticks that transmit the causal agents of Lyme
disease (Sta ord 2007).
Annual losses due to deer in Connecticut
included $1 million in lost sales to homeowners
discouraged by repeated deer damage and
$1.5 to $2.0 million in direct damages to plants
prior to sale at nurseries and garden centers
(Williams et al. 2006). More than 20% of
gardeners discontinued growing yews (Taxus
spp.), hostas (Hosta spp.), and lilies (Lilium)
because of extreme deer browse damage (Ward
2000).
A survey of Connecticut growers found that
crop-damage permits for lethal control of deer
and fencing were the only methods reported as
generally e ective 50% of the time (Williams
et al. 2006). However, in developed areas with
high housing density, use of lethal management
of deer to reduce browse damage is o en
unfeasible because of human safety concerns
and logistical and political considerations.
Fencing, alternative plant selection, or
repellents may be the only practical options in
such environments. Fencing is very e ective
but can be costly, unsightly, and restricted by
local zoning ordinances. Williams et al. (2006)
reported that 39% of growers found that
repellents were the least e ective method of
deterring deer. They also reported that 39% of
growers found repellents generally e ective,
while 44% of growers found them somewhat
e ective (Williams et al. 2006).
Over the past few decades, use of repellents
to deter deer browse damage has become
increasingly popular, especially in ornamental
se ings. Repellent manufacturers have
responded by introducing new brands and
57
Deer repellents • Ward and Williams
formulations. With so many products now on
the market, companies have developed new
formulations and application strategies, each
claiming to be be er than other products of
competitors at reducing browse damage. Sever-
al manufacturers have a empted to overcome
the problem of continued reapplication by
systemic integration of the repellent into the
plant via root uptake or foliar application. Some
companies claim their product to be e ective
for up to 3 years.
Chemical repellents can typically be classi ed
into 4 categories: fear, conditioned aversion,
pain, and taste (Beauchamp 1997, Mason 1997,
Wagner and Nolte 2001). Fear repellents emit an
odor that mimics predator scents. Conditioned
aversion repellents work by creating gastro-
intestinal discomfort. Pain inducing repel-
lents a ect the mucous membranes of the
eyes, nose, mouth, and throat. Taste-based
repellents usually include a bi er or hot-tasting
ingredient that makes the plant unpalatable to
deer (DeNicola et al. 2000).
Fear repellents
Deer survival depends on constant awareness
of their surroundings using visual, audio, and
olfactory cues. Deer may ee an area sprayed
with predator urine for fear of being ambushed
(Swihart et al. 1991). Putrid egg solids with a
sulfurous scent that mimic predator odors are
a common ingredient in fear-based repellents,
including Bobbex® (Bobbex Inc., Newtown,
Conn.), Deer-Away® Big Game Repellent
(Havahart®, Woodstream Corp., Lititz, Pa.),
and Plantskydd® (Tree World® Plant Care
Products Inc., St. Joseph, Mo.; Wagner and Nolte
2001). Liquid Fence® (Liquid Fence Company,
Brodheadsville, Pa.) also contained egg solids
in its formulation.
Conditioned-aversion repellents
Conditioned-aversion repellents can cause
some types of illnesses such as gastrointestinal
distress or nausea. Deer that consume plants
treated with these repellents will eventually
associate their distress with the consumption of
the treated vegetation. One drawback to using
such repellents is that deer need to learn to
avoid treated crops, so a signi cant amount of
damage may occur before animals become con-
ditioned. Repellents that contain ammonium
soaps of fa y acids, such as Hinder® (Matson,
LLC, North Bend, Wash.), can be found in this
category and are among the few repellents that
have been approved for usage on edible crops.
Thiram (tetramethylthiuram disul de) is a
commercial fungicide that was reported to be
an e ective browse deterrent (Conover 1984)
and was an active ingredient in Chew-Not®
(No Products Co. Inc., Coram, N.Y.). Deer
Solution® (Natural Pest Solutions, Danbury,
Conn.) is another repellent in this category as it
is formulated to simulate the smell of da odils
(Narcissus spp.), which are unpalatable to deer
(Horton and Edge 1994, Tilt et al. 1996, Kays et
al. 1997). As a result, deer are reported to learn
to avoid the treated area.
Pain-inducing repellents
Repellents that have active ingredients,
including ammonia, capsaicin, and other
naturally-occurring extracts, such as
peppermint, evoke pain when they come in
contact with the deer's eyes, gut, and mucous
membranes of the mouth and nose (DeNicola
et al. 2000). Deer learn to avoid vegetation
treated with such products due to immediate
discomfort a er consumption. Deer-O ®
(Havahart, Woodstream Corp., Lititz, Pa.) uses
some of these ingredients in its formulations.
Taste repellents
Taste-based repellents usually contain a
bi er or foul-tasting substance to make the
treated vegetation unpalatable to deer. Many
of the commercial repellents combine a taste-
based formulation with the other 3 categories
of repellents. It is safe to say that nearly all
repellents can be classi ed as taste-based, using
a variety of di erent ingredients to decrease
palatability. As a result, there are numerous
individual repellent brands that fall into this
category.
Numerous repellent trials were conducted
in the 1980s and 1990s (Conover 1984, 1987;
Andelt et al. 1991; El Hani and Conover 1997;
Nolte 1998), but few comparative studies have
been published in recent years. Li le objective
information comparing the e cacy of recent
products with those developed earlier is
available to nursery operators, landscapers,
and homeowners.
This study was conducted to compare
58 Human–Wildlife Interactions 4(1)
the e ectiveness of old and new repellent
formulations in reducing deer browse damage
over a 2-year period. We used yews (Taxus
cuspidata Densiformis) for this study because
they are palatable to deer, numerous Connecti-
cut residents have discontinued growing them
due to continued browse damage (Ward 2000),
and they have been used in past repellent trials
(Conover 1987, Swihart and Conover 1990).
Methods
Study areas
We tested repellents at 2 sites in Connecticut
during late May 2006. The Windsor study area
in northern Connecticut was an agricultural
eld adjacent to other elds that had been
repeatedly damaged by browsing. The Dawson
study area in southern Connecticut was a
periodically-mowed, grassy eld. Soils at
both Windsor (Merrimac sandy loam) and
Dawson (Agawam ne sandy loam) are mesic
Typic Dystrudepts. There was no hunting at
Windsor because of proximity to residential
housing. Dawson was a controlled access
property where hunting was prohibited.
The areas are in the northern temperate
climate zone with 1,128 mm average annual
precipitation evenly distributed over the year.
Study design
We established 2 planting blocks at each
study area. We planted 12 groups of 6 yews
in each block (72 yews per block). Each group
was planted at 0.5-m spacing between plants,
and 2-m spacing between groups within a row
and between rows. The 2-m spacing between
groups was greater than the <1 m aversion
distance for repellents reported by Swihart and
Conover (1990) and Nolte and Wagner (2000).
Blocks were separated by 2 m. We periodically
hand-weeded the blocks and applied a granular
weed control agent plus fertilizer (Preen® Step
Saver Weed Control, Preen, Lebanon, Pa.) at the
time of planting and again in May 2007. The
container-grown (2-L size) yews were donated
by Clinton Nursery, Westbrook, Connecticut.
Repellents
We randomly assigned repellent treatments
a er container plants had been planted. (The
use of trade names in this paper is for the
purpose of identi cation and does not indicate
endorsement of commercial products by the
Connecticut Agricultural Experiment Station.)
We tested 10 di erent repellent formulations:
Chew-Not®, Deer O ®, Deer-Away Big Game
Repellent®, Plantskydd®, Bobbex®, Liquid
Fence®, Deer Solution®, Hinder®, Repellex®
systemic tablets (Repellex USA, Niles, Mich.),
and coyote urine (Leg Up Enterprises, Lovell,
Me.; Table 1). Each block also had a group that
was not treated (negative control) and a group
that was protected by a metal fence supported
by metal posts (positive control). We prepared
repellents and applied them according to label
instructions. We applied Deer Solution, Bobbex,
Table 1. Deer repellents examined in a Connecticut study along with actual and recommended treat-
ment intervals (n.a. = data not available).
Number of applications Days between
treatments Recommended
treatment intervals
Treatment Windsor Dawson Windsor Dawson Label directions Days
Repellex 2 2 339 339 2 growing seasons 365
Deer Solution 5 6 107 113 Every 100 days 100
Coyote urine 24 26 17 19 A er rain n.a.
Plantskydd 3 4 168 162 Up to 6 months 180
Deer-O 7 8 70 76 2–3 months 60–90
Chew-Not 2 3 339 226 1 growing season 365
Big Game 7 8 70 76 60–72 days 60–72
Liquid Fence 13 14 34 38 1 week, then
monthly 30
Hinder 25 26 17 19 10–14 days 10–14
Bobbex 25 26 17 19 10–14 days 10–14
59
Deer repellents • Ward and Williams
Hinder, and Liquid Fence with 7.6-L tank
sprayers (Solo® Model LCS-2, Newport News,
Va.). Plantskydd, Chew-Not, and Deer-Away Big
Game Repellent using a plastic watering can. We
placed Repellex tablets directly in the root ball
at planting. We applied coyote urine directly to
co on darts and placed them between planted
yews. We purchased Deer O in a hand-spray
bo le and used it throughout the study. To
avoid potential mixing of repellents, a labeled,
dedicated sprayer, watering can, or spray bo le
was used for each repellent. Reapplication
intervals were as close as possible to label
instructions, but did vary because of weather.
Measurements and analysis
We harvested plants prior to spring growth
ush in April 2008 a er they had been exposed
to deer browsing during 2 growing and 2 dorm-
ant seasons. We measured height and width of
all surviving plants to the nearest 2.5 mm. We
cut plants at ground level at the Dawson study
area where browsing was more severe and air-
dried them in a greenhouse. A er removing
debris, we hand-stripped needles from all
plants to determine needle weights as a measure
of plant health. We dried samples at 82o C for 1
week in a forced-air oven and weighed them to
the nearest gram.
Initial experimental design for plant size was
a 2-factor (study area, deer repellent) analysis
of variance. There were 2 replicates at each
study area. Because treatment randomization
was restricted by group, each group of 6 plants
was considered a replicate to avoid potential
pseudo-replication. Therefore, average plant
measures (height, width, weight) for each
group was used in the statistical analysis,
rather than individual plant measures. There
was a signi cant interaction between study
area and deer repellent for plant size (F11,24 =
3.44, P = 0.006). Therefore, we used a separate
1-factor (deer repellent) analysis of variance to
examine plant size at each study area (Table
2). We used Tukey’s HSD test (SYSTAT 1992)
to test di erences in plant size and needle
weights among deer repellents. We considered
di erences signi cant at P < 0.05.
We used Chi-square statistics to determine
whether mortality di ered among treatments.
Di erences were considered signi cant at P <
0.05.
Protection Index (PIi) values were de ned as:
Table 2. Analysis of variance tables for the e ects of deer repellents on yew size (cm)
and needle weights (g); r2 describes how much of the variability of the dependent vari-
able can be explained by the model.
Source Sum-of-Squares df MSbF-ratio P
Size (both plots), r2 = 0.85a
Study area (SA) 160.2 1 160.2 20.1 <0.001
Repellent (R) 676.5 11 61.5 7.7 <0.001
Interaction (SA × R) 301.3 11 27.4 3.4 0.006
Error 191.1 24 8.0
Size (Dawson), r2 = 0.92
Repellent 880.9 11 80.1 14.0 <0.001
Error 68.6 12 5.7
Size (Windsor), r2 = 0.44
Repellent 97.0 11 8.8 0.9 0.593
Error 122.5 12 10.2
Needle weights (Dawson), r2 = 0.96
Repellent 153,147 11 13,922 30.1 <0.001
Error 5558 12 463
aThe r2 of 0.856 indicates that 85% of the variability in plant size can be explained with
study area, repellent, and their interaction.
bMS = mean square.
60 Human–Wildlife Interactions 4(1)
where SDi was mean size of yews on ith treatment
at Dawson; SDF was mean size of fenced yews at
Dawson; WDi was mean weight of yews on ith
treatment at Dawson; WDF was mean weight of
fenced yews at Dawson; SWi was mean size of
yews on ith treatment at Windsor; and SWF was
mean size of fenced yews at Windsor.
Results
Treatment effectiveness
Yew mortality averaged 7% and did not
di er among repellents (χ211 = 10.1, P = 0.52).
Size and needle weight did di er among
treatments (Tables 2 and 3). Unprotected yews
(negative control) were smaller than fenced
yews (positive control) at Dawson. At Windsor,
where browsing was minimal, plant size did
not di er among deer repellent treatments.
At Dawson where browsing was more severe,
only yews treated with Hinder, Bobbex, and
those protected by a fence were larger than
unprotected controls (Table 3). Plants protected
by a physical fence were 72% larger than
unprotected controls.
At Dawson, yews inside a fence had nearly
18 the needle-weights of yews that were
unprotected from deer browsing (Table 3).
Yews treated with Deer-Away Big Game
Repellent, Chew-Not, Liquid Fence, Hinder,
and Bobbex also had greater needle weights
than unprotected controls. Yews protected
by Repellex, Deer Solution, coyote urine,
Plantskydd, and Deer-O were not larger than
unprotected controls at both sites and did not
have signi cantly more needles at Dawson.
The e ectiveness of the various repellents, as
indicated by the Protection Index, varied widely
among products (Table 3).
Discussion
Comparison of earlier studies
A search of the literature found 10 pen and
12 eld studies that evaluated >1 repellent
and also had untreated plots (Table 4). There
was li le consistency in the type of damage
reported, which included plant mortality,
number of bites, amount consumed, percentage
of damage, and damage indices (Table 4).
To standardize the damage as objectively as
possible, we assumed that the level of damage
for the unprotected control to be the maximum
damage. Relative e ectiveness (%) was de ned
as 1-(Dt/Du), where Dt was damage for a given
treatment and Du was damage reported for the
untreated plots.
No repellent was 100% e ective in reducing
browse damage (Table 4). In general, egg-based
products, including Big Game Repellent, were
most e ective. Thiram and Hinder were more
e ective in eld than in pen studies. Both
repellents reduced browse damage in eld
studies to levels similar to those reported for
Table 3. Final size (cm) of yews by study area, repellent treatment, and
weight of needles (g) at the Dawson study area. See text for description of
protection index.
Final size (cm) Needles (g) Protection
index (%)
Windsor Dawson Dawson
Control 29 a 25 a 14 a 49
Repellex 31 a 23 a 25 a 50
Deer Solution 33 a 23 a 23 a 52
Coyote urine 31 a 25 a 31 a 53
Plantskydd 33 a 23 a 81 ab 60
Deer-O 35 a 28 ab 74 ab 65
Big Game 31 a 31 ab 140 bc 72
Chew-Not 33 a 29 ab 151 bcd 74
Liquid Fence 34 a 31 ab 164 cd 78
Hinder 36 a 35 bc 169 cde 83
Bobbex 35 a 36 bc 234 de 93
Physical fence 35 a 43 c 251 e 100
61
Deer repellents • Ward and Williams
egg-based products. While urine and blood-
based repellents were somewhat e ective in
short-term pen studies, they were less e ective
in eld studies. Most studies reported that
bi er-based repellents were only slightly be er
than no protections, and were actually worse
in 2 studies. Only 1 report included Bobbex in
a comparative study (Lemieux et al. 2000). In
that report, Bobbex reduced damage relative
to controls but had higher damage levels than
egg-based and bi er repellents.
Based on the present study, repellents can
provide protection approaching that of a
physical barrier such as a fence (Table 3). The
2 repellents that provided the best protection,
Bobbex and Hinder, were also the products that
required the most frequent application (Table
1). Hinder was as e ective as other products
in several eld studies (Conover 1984, 1987;
Lutz and Swanson 1997), while Bobbex was
less e ective than other repellents in a Rhode
Island study (Lemieux et al. 2000); it was only
applied twice over a 5-month period rather
than the biweekly interval during the growing
season, as suggested on the label. Bobbex was
the most expensive treatment in the study
(Table 5), had a somewhat unpleasant odor,
and required cleaning of the tank sprayer a er
each application to avoid clogging the spray
nozzle. Hinder was the second least expensive
treatment (Table 5), as it had a much lower
dilution rate (1:20) than Bobbex did (1:8), had
virtually no smell, never clogged the tank
sprayer nozzle, and unused material could be
stored in the sprayer for usage at a later time.
Hinder is also EPA registered for use on food
crops.
Yews protected by Liquid Fence, Chew-Not,
and Deer-Away Big Game Repellent were
nearly as large as yews protected by the above
repellents, and needle weights were similar to
yews protected by Hinder (Table 3; Figure 1).
Deer-Away Big Game Repellent is the most
eld-tested repellent in the literature; it has
been found to be e ective in both eld and pen
studies (Table 4). Reapplication intervals were
much longer than Bobbex and Hinder (Table 1),
and more frequent applications might improve
its e cacy. Once Bobbex was diluted, all of
the mixture had to be applied that same day,
and the tank sprayers needed to be cleaned
extensively a er each usage. Our study ranked
Chew-Not, a thiram-based product, slightly
be er than Deer-Away Big Game Repellent.
While a eld study found both repellents
o ered similar protection (Conover 1984),
pen studies reported thiram-based products
were not as e ective as Deer-Away Big Game
Repellent (Palmer et al. 1983; Andelt et al. 1991,
1992; Wagner and Nolte 2001). Thiram-based
products with a latex sticker, such as Chew-
Not, have the advantage of very long intervals
(>180 days) between applications. However, the
latex sticker required extensive mixing, use of a
watering can to apply it, and extensive cleanup.
In addition, thiram is an EPA-registered
fungicide, which may require a pesticide
applicator’s license for its application.
We could nd no published eld trials in
the scienti c literature that used Liquid Fence.
Liquid Fence ranked high on our Protection
Index, and total costs were low (Tables 3 and
5). Liquid Fence did not need to be applied as
frequently as Hinder or Bobbex or a er rain (1
week a er initial treatment and every 30 days
therea er), and it ranked just behind both in
our Protection Index. Liquid Fence did not clog
tank sprayers, and excess material could be
stored in sprayers for usage at a later time.
Four of the repellents (Repellex tablets, Deer
Figure 1. Applying Chew-Not deer repellent on yews. No repellent was 100% effective.
62 Human–Wildlife Interactions 4(1)
Table 4. Comparison in percentage of repellent e ectiveness relative to unprotected controls. Higher values indicate greater control (0% = no di er-
ence from unprotected controls; 100% = no damage). Period = duration of study; wk. = week; mon. = month; yr. = year.
Pen studies (% e ective)
Study Cervida Period Plant BGR-LbBGR-P Eggs Urine Hinder Blood Thiram Bi er
Andelt et al. (1991) MD <1 wk. Feed 81 82 80c55 58 20
Andelt et al. (1992) Elk <1 wk. Medicago 72 53 86c41 38 3
Nolte et al. (2001) BT 2 wk. Thuja 91 10f
Palmer et al. (1983) WT 2 wk. Cornus 73 49 18
Kimball and Nolte (2006) BT 3 wk. Thuja 99 39d
Kimball et al. (2005) WT 3 wk. Thuja 99
Sullivan et al. (1985) BT 3 wk. Gaultheria 94g92c
Melchoirs and Leslie (1985) BT 1 mon. Gaultheria 12 86 18e
Nolte (1998) BT 14 wk. Pinus and
Thuja 76 76d68 4
Wagner and Nolte (2001) BT 18 wk. Thuja 44 12h16c032
d12 12
—pen studies 56 90 60 51 36 49 39 10
Table continued on next page.
63
Deer repellents • Ward and Williams
Table continued.
Field studies (% e ective)
Study Cervida Period Plant BGR-LbBGR-P Eggs Urine Hinder Blood Thiram Bi er
Lutz and Swanson (1997) WT 2 wk. Feed 89 41c90 18
Baker et al. (1999) Elk 5 wk. Populus 24
Milunas et al. (1994) WT 6 wk. Taxus 31
Santilli et al. (2004) FD 8 wk. Olea 28i23
Swihart et al. (1991) WT 8 wk. Taxus
and
Tsuga 11c
Swihart and Conover (1990) WT 5 mon. Taxus 76 -7
Lemieux et al. (2000) WT 6 mon. Ilex and
Taxus 90j56
Conover (1984) WT 6 mon. Taxus 47 44 52
Conover (1987) WT 6 mon. Taxus 50 48
Witmer et al. (1997) Deer and
elk 7 mon. Conifer 67 86 -5
Bergquist and Örlander (1996) RD 8 mon. Pinus
and
Picea 13
Conover and Kania (1988) WT 1 yr. Malas 25
eld studies 54 58 90 26 61 63 52 16
—all studies 55 81 66 44 47 55 41 14
aElk (Cervus elaphus), RD (Capreolus capreolus), FD (Dama dama), MD (Odocoileus hemionus), BT (Odocoileus hemionus columbianus), WT (Odocoileus
virginianus).
bBGR-L = Big Game Repellent liquid; BGR-P = Big Game Repellent powder.
cCoyote urine.
dPlantskydd.
ePredator fecal extracts.
fWol n (synthetic wolf urine).
gunreported commercial product.
hMr T’s Deerblocker and Not Tonight Deer.
iEutro t.
jHolly Ridge.
64 Human–Wildlife Interactions 4(1)
Solution, coyote urine, and Plantskydd; Table
3) that we evaluated provided no signi cant
reduction of browse damage relative to
unprotected controls. Most studies reported
that repellents using a bi er compound, such
as Repellex, are ine ective (Table 4). The
addition of bi ering agents as repellents did
not decrease feed consumption for several
herbivores (Nolte et al. 1994, Wright and Milne
1996). Levels of bi ering agents su cient to
deter browsing were phytotoxic and resulted
in >75% seedling mortality (Bergquist and
Örlander 1996). Repellex tablets were easy to
plant with the shrubs and were inexpensive
(Table 5), but were ine ective. In addition,
the use of systemic repellents would likely be
undesirable for produce and other food items.
Short-term pen studies suggested that
predator urine provided short-term (<1 month)
protection from browsing (Table 4). Our results
found that urine o ers li le longer term
protection; deer were observed browsing on
yews treated with urine within 2 months of the
initiation of the study. Another study showed
that coyote urine sprayed on yews was much
more e ective in reducing browse damage
than urine applied from tubes with co on darts
(Swihart et al. 1991). Coyote urine costs were
moderate (Table 5). Coyote urine was easy to
apply, but it smells bad to humans, too.
The e ectiveness of blood-based repellents,
including Plantskydd, has varied among studies
in other regions (Table 4). Casual observation
during the rst growing season suggested
Plantskydd was e ective; however, damage
was signi cant by the end of the experiment
(Table 3). Plantskydd, which consisted of dried
bovine blood, had to be mixed in a watering
can, and when applied looked and smelled
like blood. Costs were moderate (Table 5), and
e ectiveness may have been enhanced with
more frequent application.
We could nd no published eld trials of
Deer Solution in the scienti c literature. Deer
Solution had a pleasant odor, costs were
moderate (Table 5), did not clog spray nozzles,
and could be stored in sprayers over time. While
we found Deer Solution was not e ective in our
study (Table 3), it may have been more e ective
with a more frequent application schedule.
While proper physical exclusion can prevent
100% of browse damage by white-tailed deer
at a one-time cost and minimal long-term
labor, fencing can be unsightly and expensive
to install. Commercially available repellents
provide an alternative to fencing, but are not
as e ective. The selection of which repellent
to use is a trade-o between e ectiveness, cost
(material and time), ability or willingness to
follow reapplication interval, and plant species
to be protected. Our research has shown that
generally, repellents that were applied more
frequently ranked higher on our Protection
Index.
Acknowledgments
We thank the South Central Connecticut
Regional Water Authority for providing a eld
site; Clinton Nurseries, Clinton, Connecticut,
and Sunny Border Nursery-Kensington,
Connecticut, for plant donations; and J. P.
Barsky, G. M. Picard, R. Vidro, D. V. Tompkins,
R. A. Wilcox, and E. A. Kiesewe er for assistance
with plot maintenance and data collection. This
research was partly funded by Hatch Project
CONH-0560.
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66 Human–Wildlife Interactions 4(1)
JEFFREY S. WARD earned his B.S. and M.S.
degrees at Ohio State University, and after a stint
in the Peace Corps, his
Ph.D. degree at Purdue
University. He is currently
the Chief Scientist in the
Department of Forestry
and Horticultural at the
Connecticut Agricultural
Experiment Station. His
research on alternative
methods of reducing
deer browse damage
in plantations began
in 1990. Other current
studies include controlling
invasive woody plants
and long-term population dynamics of unmanaged
and managed forests.
SCOTT C. WILLIAMS earned his bach-
elor’s degree from Connecticut College, his
master’s degree from the
Yale University School
of Forestry and Envi-
ronmental Studies, and
his Ph.D. degree from
the University of Con-
necticut. He is currently a
Research Scientist in the
Department of Forestry
and Horticulture at the
Connecticut Agricultural
Experiment Station in
New Haven.His research
focuses on the detrimen-
tal impacts of overabun-
dant deer on public health, agricultural crops, and
forested ecosystems.
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An experiment was performed in 4 commercial nurseries in Connecticut to compare the effectiveness of BGR, Ro.pel, and Ivory soap in reducing browse damage by white-tailed deer Odocoileus virginianus to Japanese yews Taxus cuspidata. BGR was the most effective compound reducing damage 76.0% relative to untreated plants, whereas Ivory soap reduced damage 37.6% and Ro.pel did not significantly reduce damage. Soap was effective in reducing damage to twigs ≤1 m from a bar of soap for both yews and apple trees, but protection was weak or not evident at greater distances. -from Authors
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Browsing reductions for the predator feces tested were: bobcat Felis rufus-51%; mountain lion F. concolor-27%; wolf Canis lupus-17%; and coyote C. latrans-8%. The efficacy of fecal extracts correlated with the concentration of predator feces in initial formulations (5, 10 and 20% by weight). Increasing the concentration of feces to 30% for bobcat and mountain lion did not increase their repellency. Fecal odors of predators significantly suppressed the feeding activities of black-tailed deer Odocoileus hemionus columbianus.-from Authors