INFLUENCE OF BODY CONDITION ON VIGILANCE IN MULE DEER (Odocoileus hemionus) & WHITE‐TAILED DEER (Odocoileus virginianus) UNDER RISK OF PREDATION Julianne Hower
University of Washington, School of Environmental and Forest Sciences I examined the relationship between
individual anti-predator behavior and
physical body condition of mule deer and
white-tailed deer in areas of Eastern
Washington.
Animal-borne video footage has been
analyzed from both species of deer, and
behavioral data collected. I performed a
linear regression with body condition
versus time spent vigilant by comparing
the amount of time spent vigilant* as a
function of foraging time.
I predicted that the prey individuals with
substandard body condition would invest
more in anti-predator behavior than
those individuals with good body
condition, but this prediction was not
supported.
RESULTS
INTRODUCTION
The asset-protection principle (Clark 1994)
predicts that prey animals in good body
condition should invest more in anti-predator
behavior (i.e., vigilance) than animals in poor
body condition.
I predicted that deer with relatively good body
condition would spend more time vigilant
during foraging bouts. I assessed body
condition and anti-predator behavior in mule
deer and white-tailed deer in a system with
multiple predators, including cougar (Puma
concolor), gray wolf (Canis lupus), and coyote
(Canis latrans).
Results showed a non-significant relationship
between vigilance and body condition (Figure 2).
Vigilance was considered the dependent variable,
and body condition was considered the
independent variable (Table 1). Thus, I failed to
reject the null hypothesis of no relationship between
condition and vigilance.
Proportion of time vigilant (arcsin)
ABSTRACT
R2 Linear = 0.061
Figure 1b. White-tailed deer vigilant
Figure 2. Linear regression of the relationship between body condition and
arcsin of the square root transformed proportion of time spent vigilant
Coefficients**
Unstandardized
Coefficients
METHODS
Field Methods: Camera collars were fitted
onto 38 individual deer to record their behavior.
Animal-borne video footage was analyzed to
quantify how much time each deer spent
foraging (Figure 1a) versus vigilant (Figure
1b). Body condition (Figure 1c & 1d) was
determined using ultrasonography to measure
rump fat thickness (mm).
Statistical Analysis: Video footage from 9
deer was used for the analysis. A linear
regression was performed examining the
relationship between condition (mm of rump fat
thickness) and arcsin of the square root
transformed proportion of time spent vigilant.
Figure 1d. Emaciated deer
DISCUSSION
Body condition (mm rump fat)
*Deer were considered vigilant if their heads
were up (rather than head-down, foraging).
Figure 1c. Healthy deer
Figure 1a. Mule deer foraging
Model
1 (Constant)
condition
B
Std. Error
.776
.448
.023
Standardized
Coefficients
Beta
.034
t
Sig.
1.732 .127
.247
.673
.522
Although there was a non-significant
relationship between body condition and
vigilance, there was a trend of increased
vigilance with increasing body condition, which
is consistent with the asset-protection principle.
This trend indicates the need for more study
with a larger sample size.
With the re-establishment of wolves in
Washington, it is important to understand how
they will affect deer anti-predator behavior
(e.g., vigilance). Such an effect could change
deer foraging, which can potentially alter the
vegetation of habitats and impact deer
population size. REFERENCES
** Dependent Variable: asinvig
Table 1. Results from a linear regression (SPSS)
ACKNOWLEDGMENTS
I would like to thank Aaron Wirsing for his guidance
and assistance, Justin Dellinger for allowing me
access to his field work and video footage, and all
of the students who helped view the countless
hours of video footage.
LITERATURE CITED
1. Clark, C.W. 1994. Antipredator behavior and the
asset-protection principle. Behavioral Ecology
5:159-170.
2. Heithaus, M.R., Frid, A., Wirsing, A.J., Dill, L.M.,
Fourqurean, J.W., Burkholder, D., Thomson, J., &
BejderO, L. 2007. State-dependent risk-taking by
green sea turtles mediates top-down effects of tiger
shark intimidation in a marine ecosystem. Animal
Ecology 76, 5: 837-844.
3. McNamara, J.M. & Houston, A.I. 1987. Starvation
and predation as factors limiting population size.
Ecology 68: 1515–1519.