Effects of the Addition of Coyote Urine on
Whitetail Deer Feeding Behavior at Established Feeding Sites
Jenna Barlow & Nathan Sylte
INTRODUCTION
Whitetail
deer (Odocoileus virginianus) are
common throughout North America and thrive within diverse habitat regions, many
of which have extreme temperature swings between seasons (Rooney 2001). The
ability to inhabit regions that experience extreme cold as well as intense warm
spells makes the whitetail deer an excellent model homeotherm. Homeotherms are
presented with a metabolic challenge during winter months; therefore, whitetail
deer must allocate their time in order to consume enough food, but also balance
this with rumination, movement, social interactions, and sleeping (Beier and
McCullough 1990). Another important part of the activity budget is
vigilance. Increased time spent on
vigilance reduces predation risk, but vigilance conflicts with some types of
feeding (Benhaiem et al. 2008). Deer have many predators—for example, coyotes
that have been observed in packs killing whitetail deer (Gese and Grothe
1995)—and so it is reasonable to expect there will be strong selection for
optimizing the ratio of time spent vigilant to time spent feeding. So with the
use of predator urine as the apparent risk of a nearby predator, it would be
expected that this ratio would shift to more time spent being vigilant and less
on feeding.
The
introduction of predator urine to feeding sites has been shown to significantly
decrease deer browsing (Swihart et al. 1991). This has important management
implications because winter browsing by deer often damages nurseries, natural
restoration of timber species, and substantial agriculture crop damage (Swihart
et al. 1991; Bellant 1998). Browsing by
deer has also been found to significantly influence forest ecosystems (Rooney
and Waller 2003). However, there appears to be little published information on
the effect of predator scents on deer feeding and vigilance, though Benhaiem et
al. (2008) has found that the more time spent being vigilant when exposed to
predation risk can have significant consequences on roe deer energy budgets.
Our objective is to study the effects on the whitetail deer activity budget by
artificially increasing the apparent predation risk via coyote urine.
METHODS
Four
feeding locations baited with corn were established prior to the beginning of
the experiment. Sites were established one week in advance on February 29, 2016
to allow deer adequate time to find the sites. From that date on the sites were
re-baited with corn every three days. Three sites are located in Dunn County
and the fourth is in Chippewa County. All sites are located near woodland
edges. Three of the four sites are located at or near a field edge, and the
other is in a forest clearing; all sites are at least 200 meters from known
deer bedding sites. Our site selection was designed to force the deer out of
their comfort zones and into areas farther from cover (and thus be exposed to
higher predation risk). Another factor in determining where sites were to be
located was the proximity of the sites relative to each other; they were placed
at least one mile apart to ensure the same deer were not using multiples of the
established feeding sites. Lastly, feeding sites were placed in areas with high
whitetail activity, as determined by physical signs such as tracks, heavily
used trails, and fecal matter.
To
record data for the experiment, infrared/motion detecting cameras were selected
as the most practical option, for they are minimally invasive and can record
data for months at a time. On March 7, approximately one week after feeding
sites were established, the motion cameras were placed at the four sites. After
a 10-day period without coyote urine being present, coyote urine was added to
each of the four sites. Several ounces of urine were deposited on a small log
that could easily be removed after the 10-day period was up. Five days after
the urine was originally added, several more ounces of fresh urine were added
to each of the sites. This was done to simulate the frequent presence of a
predator. After 10 total days of urine being present, the logs the urine was
placed on were removed and the cameras were collected. Unfortunately, the
camera at site two turned out to have some technical difficulties and data was
unable to be collected from this site. Site two had to be excluded from the
experiment.
The variables analyzed in the
experiment included total deer activity, percent of deer feeding, percent of
deer being vigilant, and time of activity measured by night or day. Total deer
activity was measured in each of the two, 10-day periods based on the total
number of deer in pictures taken and by the number of pictures taken with deer
present. The time of day at which feeding occurred was also measured and was
recorded as either day or night, using sunrise and sunset times to establish
whether it was day or night. Alertness was measured by counting the number of
deer appearing in an alert posture in the pictures. An example of an alert
posture includes a deer looking up and away from the feeding site with its ears
up. Deer feeding was measured by the amount of deer with their heads in the
down posture. The proportion of deer in the picture in an alert posture, as
well as the proportion of deer feeding were also taken. Presence of coyote
urine represented the independent variable in the experiment. T-tests were used
to measure for significant differences in the data. Chi-squared tests were also
used in data analysis. Specifically, a Pearson's Chi-squared test with Yates'
continuity correction was used.
RESULTS
Overall, whitetail deer spent
proportionally more of their time
feeding (50%) compared to the time they spent being in the alert posture
(30%, p<0.001). So, in general, deer budgeted more time feeding than openly
being vigilant (Figure 1). To support our initial prediction, with the addition
of the coyote urine to the sites, the proportion of alertness significantly
increased, based on a t-test. The proportion of alertness increased from 0.29
to 0.37 (p=0.018).
Across each of the
three sites, the presence of urine tended to increase deer activity during the
day. In all three sites, the proportion of time spent feeding when there was no
urine present was drastically different comparing day and night. This indicates
that at each site the deer had a preference to feed at one time versus the
other. Whereas when there was urine present the proportion of time spent
feeding was often the same amount for both day and night, suggesting the urine
affected their willingness to feed. Specifically, shifting deer feed more with
the presence of light. This was
especially shown in site 4. There was also always a greater proportion of deer
feeding when there was no urine added. There is a pattern that emerges in
Figure 3, the higher frequency of feeding either day or night remained the same
even with the addition of the urine.
DISCUSSION
Our
hypothesis that the addition of coyote urine would impact whitetail deer
feeding behavior with regards to vigilance/alertness and willingness to feed
was supported by our results. It should first be noted that deer behaved
differently at each site. Night feeding was prefered at site four, while deer
prefered to feed during the day at site three.
At site one, the deer tended to feed at night; however, there was more
variation in their feeding times. With the presence of coyote urine, deer
tended to feed more during daylight hours, while without the presence of urine
they fed more at night. This indicates that the presence of coyote urine
impacted their willingness to feed at night. This makes sense considering
coyotes are more active at night (Andelt 1985). Although the presence of coyote
urine did not stop deer from feeding at the sites, it did alter their feeding
schedule as well as their budgeted time in feeding and alertness. The fact that
the presence of coyote urine didn’t completely stop the deer from feeding at
the sites demonstrates how important calorie replacement is for whitetail deer.
Proportionally,
whitetail deer spent more time feeding than they did in an alert posture
(Figure 1). This is logical considering they would never be able to obtain the
necessary calories to survive if they spent a majority of their time in an
alert posture instead of feeding. With the presence of coyote urine, the budget
for this behavior was altered. Whitetail deer were significantly more alert
with the presence of urine than without (Figure 2). Therefore, they did not
spend as much time feeding as they otherwise would have. This result does not
contradict the study of Swihart et al. which found that the presence of
predator urine significantly reduced deer browsing.
Temperature
may have represented an important potential covariate in our experiment.
Although the effects temperature had on whitetail feeding behavior were not
directly measured in our experiment due to camera complications, temperature
has been shown to influence deer activity (Beier and McCullough 1990). It is
possible that some of the cooler temperature swings during the second part of
the experiment (urine present) influenced the deer to feed more during the day.
However, the extent to which temperature influenced whitetail deer feeding
behavior in our experiment is uncertain. Future studies may want to better
analyze how temperature influences whitetail feeding behavior. It is possible
that whitetail may be more vigilant during colder time periods and may spend
substantially more time feeding during the day.
Overall,
studying animal behavior is difficult but important. At any point in time there
may be many different variables influencing the way an animal is behaving,
which makes studying how animals behave in the wild challenging. There is still
much knowledge to be gained in the study of homeotherms and homeothermy.
Further advancements in the study of homeotherm behavior will only benefit our
overall knowledge of homeothermy.
REFERENCES
Andelt,
W. F. (1985). Behavioral Ecology of Coyotes in South Texas. The Wildlife Society, 94, 3-45.
Allen, E.O.
1968. Range use, foods, condition, and productivity of white-tailed deer in
Montana. The Journal of Wildlife Management 32:130-141.
Beier, P. and D.R. McCullough. 1990.
Factors influencing white-tailed deer activity patterns and habitat use.
Wildlife Monographs 109:3-51.
Bellant, J.L., T.W. Seamans, and
L.A. Tyson. 1998. Predator urines as chemical barriers to white-tailed deer.
Proceedings of the Eighteenth Vertebrate Pest Conference Paper 4.
Benhaiem, S., M. Delon, B. Lourtet,
B. Cargnelutti, S. Aulagnier, A.M. Hewison, N. Morellet, and H. Verheyden.
2008. Hunting increases vigilance levels in roe deer and modifies feeding site
selection. Animal Behaviour 76:611-618.
Gese, E.M. and S. Grothe. 1995.
Analysis of coyote predation on deer and elk during winter in Yellowstone
National Park, Wyoming. The American Midland Naturalist 133:36-43.
Rooney, T.P.
2001. Deer impacts on forest ecosystems: a North American perspective.
Forestry
74.3:201-208.
Rooney T.P. and D.M. Waller. 2003.
Direct and indirect effects of white-tailed deer in forest ecosystems. Forest
Ecology and Management 181:165-176.
Swihart, R.K., J.J. Pignatello, and
M.J.I. Mattina. 1991. Aversive responses of white-tailed deer, Odocoileus virginianus, to predator
urines. Journal of Chemical Ecology 17:767-777.
No comments:
Post a Comment