By Mason Lee, Texas A&M WFSC '15 and Blake Alldredge, Texas A&M AgriLife Extension Service
Trail
cameras are becoming increasingly popular in both scientific and recreational endeavors. They are widely used as a way to scout an area for white-tailed deer
bucks prior to hunting season and when trapping
feral hogs, but they are not restricted to these uses. They can be
used as powerful census tools in wildlife management. Cameras can provide the
user feedback on their targeted species’ range size, nesting information, and
demographic features such as population size, age structure, and sex ratios.
In
addition, cameras can also capture information about predators and how they
interact with prey. For example, cameras have become invaluable for determining
which predator species are the most detrimental for upland game bird nesting
success. Studies on northern bobwhite, Rio Grande wild turkey, and Eastern wild
turkey are providing information as to the most common predators and features
(grass height, shrub density, etc.) that best conceal nest sites from
predators. A camera study on Eastern wild turkey nests found that American
crows (Corvus brachyrhynchos) preyed on more nests than any other species
(Melville et al. 2014). Raccoons (Procyon
lotor) and Virginia opossums (Didelphis virginiana) were the top mammalian nest
predators. Information such as this is valuable when conducting mammalian predator
control programs as it identifies the greatest predator threat to game species.
Because of this, “camera trapping” has been included as a key component of the Texas
Quail Index, which is a statewide monitoring effort
to evaluate quail populations.
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| A raccoon (Procyon lotor) depredates a nest. |
There
are multiple benefits of using trail cameras to survey populations of game and
non-game species. Cameras are less invasive, less time consuming, less costly,
capable at working during the night and in inaccessible locations, and useful
for recording elusive or behaviorally aggressive animals. In addition, cameras can
store data for a long period of time. This may reduce bias in surveys by
allowing observers unlimited time to review the data (Cutler and Swann 1999), in
contrast to other survey methods where only one observer has to gather data in
a brief amount of time.
Camera
surveys also offer an unbiased alternative to road surveys for white-tailed
deer. In areas where there are few roads, surveyors may utilize a non-random
sampling transect by only surveying areas close to the road, since those
locations are the easiest to sample. This neglects other areas that are
inaccessible to people, which can produce biased data. Cameras eliminate this
bias by allowing sampling to easily occur in otherwise difficult-to-survey
areas (Roberts et al. 2006). Cameras can also reduce bias by providing pictures
of an individual animal from a few different angles, which allows the observer
to accurately assess body size and condition. Multiple angles also help
observers construct a more accurate identification of individuals.
The
type, location, and number of cameras used for wildlife management will depend on
the management objectives. There are two types of cameras that can be used: motion-triggered
cameras and time lapse cameras. Motion-triggered cameras are the better choice
when the animal being surveyed occurs infrequently and has a wide range (Cutler
and Swann 1999). This will ensure that the animal is captured if it walks into
the camera’s frame. Time lapse cameras are most beneficial if the target
species occurs frequently in the frame (such as at nest sites), when the
activity of interest occurs often, or when nothing else occurs in the area that
might trigger the camera. This camera method produces a portrayal of activity
throughout a given time span.
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| A camera is set up on a tree. |
Before
placing cameras, review a map or aerial view of the property. Then, use a grid
to divide the area into cells that are equal to the number of cameras that will
be used. For example, if 5 cameras will be used, the property should be divided
into 5 cells. The camera should be placed near the middle of each cell that was
created (University of Missouri Extension 2012). Placing the cameras in this
pattern will ensure that each area of the property is accurately represented
and will help to reduce bias in the survey results.
It
is also important to place cameras near frequently used trails instead of only
placing cameras that face feeders and other baited sites since this produces
significantly biased results when trying to identify population demographics. Not all sexes or age classes use baited areas
equally, which can skew the ratios (McCoy, Ditchkoff, and Steury 2011). Cameras
that are situated along frequently used trails will provide data that is more
representative of the actual population than cameras that are at baited sites.
 |
| A camera faces a feeder. This set-up can cause biased results. |
Although
camera surveys can provide accurate results, it is still recommended that they
be supplemented by another survey method for a more accurate estimate of the
target population. For example, road surveys may still be conducted for a
couple of years to compare the data between both survey methods. Also, the
condition of the habitat can provide helpful feedback regarding wildlife
density. If the range is over browsed by deer, then populations need to be
reduced. Conducting a browse survey or walking around the property to examine
how deer are utilizing key food species will provide more useful information than
only estimating how many deer are on the property. This is because deer affect
each property differently depending on the availability of food resources and
other pressures, such as predation. Do not rely solely on cameras to make
decisions without seeing how the wildlife population is interacting with the
property.
For
information on how cameras can be used for different target species and a data
sheet for camera surveys, read “Potential Uses for Trail Cameras in Wildlife
Management” at the AgriLife
Bookstore. In addition, this
webinar can be accessed for information about different
survey methods for white-tailed deer.
Literature Cited
Cutler, Tricia L., and
Don E. Swann. 1999. Using remote photography in wildlife ecology: a
review.
Wildlife Society Bulletin 27: 571-581.
McCoy, Clint J.,
Stephen S. Ditchkoff, and Todd D. Steury. 2011. Bias associated with baited
camera
sites for assessing population characteristics of deer. Journal of Wildlife
Management 75:472-477.
Melville, I.A.S., W.C.
Conway, M.L. Morrison, C.E. Comer, and J.B. Hardin. 2014.
Artificial
nests
identify possible nest predators of Eastern wild turkeys. Southeastern Naturalist
13
(1): 80-91.
Roberts, Clay W., B.L.
Pierce, A. W. Braden, R. R. Lopez, N. J. Silvy, P.A. Frank, and D.
Ransom,
Jr. 2006. Comparison of camera and road survey estimates for white-tailed
deer.
Journal of Wildlife Management 70: 263-267.
University of Missouri
Extension. 2012. Estimating deer populations on your property: camera
survey.