Wildlife
Spotlight and Daylight Cruise Survey of Deer: Collecting and Interpreting Data
By Russell Stevens, The Samuel Roberts Noble Foundation T
he spotlight survey is widely accepted as a practi- cal method of estimating deer population trends in
areas with openings in timber and brush. Deer density and buck-to-doe and doe-to-fawn ratios obtained from spotlight surveys are merely estimates, with deer den- sity being the most useful.
Selecting spotlight survey routes Select permanent survey routes after a careful ex-
amination of the ranch’s habitat types. Survey routes should follow all-weather roads so inclement weather will not prevent sampling of particular areas. The selected route should sample each area only
once and traverse habitat types (upland brush, bermu- dagrass pasture, cropland, bottomland timber, native range, etc.) in proportion to their existence on the ranch. Do not include a route leg only because it crosses
known deer concentrations; the survey is only a sample of a portion of the habitat on the ranch and must be as representative as possible. Longer routes are better if they can be completed
within 3 to 4 hours. Observer fatigue and weather changes can be a problem on longer routes. The same route should be used each year so data will be comparable among years.
When to conduct spotlight and daylight cruise surveys Spotlight surveys conducted in late August or in
September allow the observer to identify the sex and age of deer more accurately. Earlier in the season, fawns are more diffi cult to see
because they are smaller and less mobile, and bucks’ antlers may not be well developed. Later in the season, fawns may be large enough to confuse with does. Surveys generate information that helps determine
harvest quotas and is most useful before deer hunt- ing season. To minimize sampling bias, choose a consistent time
to begin each spotlight survey, but start no earlier than one-half hour after sunset. A minimum of fi ve surveys conducted within a 2- to 3-week period minimizes the infl uence of weather and other factors on deer activity. Ideally, wind speeds should not exceed 15 to 20 miles
82 The Cattleman January 2017
per hour, there should be no rain and the temperature should not be excessively high. Always notify the local game warden before each
spotlight survey is conducted. Sample size for buck-to-doe and doe-to-fawn ra-
tios can be supplemented by mobile or cruise surveys conducted just after daylight. Daylight cruise surveys should be conducted at the same time of the year as spotlight surveys. Ideally, a minimum of 100 deer should be identifi ed for data interpretation.
Equipment used to conduct spotlight surveys A large plastic storage container can be used for
seating and holding equipment: 2 magnetic antennas to serve as “spider web catchers” when placed on the vehicle’s cab; spotlights powered by a battery attached to homemade cable; tape to secure the cable to the vehicle; extra batteries and spotlights. Spotlights with 400,000 candlepower work best. The person recording the data can use a small
fl ashlight so the dome light can remain off and reduce windshield glare for the driver. Two-way headsets are a convenience that can en-
thecattlemanmagazine.com
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