Field Guide 54 · Trail Cameras & CountsFlash type · Deer reactions · Card checks · Camera placement
Deer notice the flash and keep coming, and card checks may cost photos
FDR Research Desk · Field-craft, method, and evidencePublished
Nearly every camera hunter has a frame of a buck locked on the lens. A deer tearing out of the shot is just as familiar. One frame will not separate a deer that left the trail from a deer that only broke stride. A flash reaction can show up while that deer keeps using the spot. This search found one white-tailed deer test. It points at the person walking in to pull that card. Our rule is to cut down those walks where you intend to hunt, and only afterward worry over the lamp.
STEP 1 · Flash type
German deer looked harder at 850 nm while photo rates held steady
Henrich and colleagues scored red deer along with roe deer during 900 camera deployments in the Bavarian Forest National Park and the Northern Black Forest in Germany. Whitetails were absent from that sample. Fewer reactions were expected once the wavelength got longer. The lamps were a 940 nm black flash, an 850 nm standard infrared flash and white flash. Henrich and colleagues found a higher chance of reaction under standard infrared compared with black flash in each species. Delayed triggers blocked any comparison against white flash.
Henrich and colleagues report stares at the camera for about 31 percent of events with red deer and for about 8 percent of events with roe deer. Flight was more common in red deer than in roe deer. For a red deer, more distance from the camera lowered the chance of a stare and the chance of flight. Stares and flight were rarer in the park than in the Northern Black Forest. Hunting in the park sits under severe limits.
After dark, black-flash passes looked like daytime passes with no lamp. Henrich and colleagues treat the 940 nm lamp as beyond what these deer see. The cone studies they cite used fallow deer and white-tailed deer. Those cones peak in the blue and the green. Red-range light may go unseen when light is low. The photos still showed a stronger response under the 850 nm flash. The authors read that pattern as these deer detecting the infrared beam or the red shine around the lamp.
For the rate work the authors report 881 deployments that each ran 26 days at most. They split into 448 black flash, 400 standard infrared and 34 white flash. Over those days, free-ranging deer produced photo rates with no significant drop for any flash type or for either deer species in the test. If behavior is the question, Henrich and colleagues still want the longer-wavelength flash because it disturbs the deer less. When counting passes, they treat every flash type as usable and tell you to choose by detection range and by picture quality.
Henrich and colleagues recommend a setback beyond 16 feet (5 m) from a game path when behavior is the aim. They draw that figure from red deer together with roe deer in those two forests.
STEP 2 · Shutter click
Chamber mics found clicks inside mammal hearing
Meek and colleagues recorded 12 camera models in an anechoic chamber. Ultrasound was measured on five models and infrared output on seven. Meek and colleagues reported clicks that sit in the audible band of most mammals on their list, plus illumination many species are able to see. Published curves for 21 mammal species supplied the hearing comparison. The work measured cameras in a chamber and included no deer.
On the quiet model used as the benchmark, 10 units averaged 7.6 to 27.1 dB from 12.5 to 20000 Hz. The microphone was about 20 inches (50 cm) away from the camera.
Our sight and sound guide covers chamber pitches where whitetail hearing peaked. The camera band reaches that upper range.
A chamber threshold and a bolt at a trail click are separate questions. Meek and colleagues note that each added 3.3 feet (1 m) is expected to cut about 6 dB. No paper opened here measured the click out at field distance.
The no-glow model in the test averaged 940.5 nm. The two shorter-wavelength models averaged 828.3 nm and 844.1 nm. Models sold as no-glow ran above 850 nm. Meek and colleagues also name scent from a person on the box plus the outline against the tree. An animal might notice a camera from either cue. Both cues were left unmeasured.
STEP 3 · The check
Fewer whitetail photos came with unmasked visits at one of the two sites
Muñoz and colleagues tested camera checks on white-tailed deer in the North Carolina Piedmont. Haw River in Alamance County is private alluvial woods covering roughly 40 acres (16.2 ha). Rocky River in Chatham County is oak-hickory woods covering roughly 32 acres (12.9 ha). Eight cameras went to each site. Each site had four cameras checked by people wearing ordinary field clothes. Carbon clothing went with scent-masking soap and a housing spray for the other four. Mounts were roughly 9 to 11 inches (23 to 27 cm) above the soil. A no-glow flash kept the lamp from riding along in the scent contrast.
Checks started after a month with no visits and then came every two weeks. Haw River dates ran early February through mid-July of 2011. Thefts ended that site once each camera had logged 158 trap-nights. Rocky River dates ran September 2011 through early March of 2012. Each camera there logged 210 trap-nights. Mammal captures totaled 2085 at Haw River and 3358 at Rocky River. An animal remaining in the frame counted as a single capture.
Muñoz and colleagues found the treatment difference in white-tailed deer at Haw River alone. Masked cameras averaged 5.23 deer captures per two-week survey period. Unmasked cameras averaged 3.38. The 95 percent interval was 4.1 to 6.6 on masked cameras and 2.5 to 4.5 on unmasked cameras. Relative to the unmasked mean, the masked mean is about 55 percent higher per period. The statistics supported that gap. Other species lacked a clear treatment effect. So did white-tailed deer at Rocky River.
In the month before any treatment, cameras later masked averaged 4.75 deer captures. Cameras later left unmasked averaged 16.75. On the 16.75 figure the standard error reached 15.5. Our read is that one camera or two cameras carried that high average. After the checks began, the masked set was busier. The authors read that switch as an effect of scent. Each camera sat roughly 250 to 490 feet (75 to 150 m) from the nearest other camera. Our read is that one walk could lay scent on the next station. Masked cameras were visited on the day after the unmasked cameras. Clothing, soap, spray and the day of the walk formed one package. The paper leaves open which item in the package shifted deer behavior. Muñoz and colleagues state that the time scent remained is unknown.
The Haw River run missed the local hunting season. Hunting still went on next door. At Rocky River a hunter and hikers appeared on the site while the work was underway. The authors suggest that a hunted deer may connect human odor with risk.
STEP 4 · Field test
Watch the walk for two weeks before moving a lamp
For behavior, use the longer-wavelength flash and keep more than 16 feet between the camera and the trail. That spacing is the German authors' figure for red deer and for roe deer. For a pass count, the same study found photo rate without a significant decline on deployments lasting up to 26 days. A single frame with a stare is a weak cause for pulling the set.
On ground you hunt for whitetails, that caution belongs with the approach to the camera. Muñoz and colleagues say that where you place a camera and when you run the survey may matter more than masking human odor for species with no aversion to human activity. None of the studies opened for this piece gives a safe span between checks. On the two-week gap at Haw River, ordinary-clothes cameras still produced fewer deer pictures. That site is one of two. The contrast was the full checking routine.
Our rule is to skip a card-only trip on ground you mean to hunt. Make the pull during a hunt already planned. Our scent guide found no measured distance for how far off a deer detects a person, and no deer test that used carbon cloth alone. What the Piedmont study changed was the whole check routine.
A reaction also shifts a herd estimate built from photos. Our camera-count guide shows a buck-to-doe figure taken off a photo card as a ratio among the pictures. It follows the herd only if a doe hits the camera as often as a buck does. A bolt from the lamp changes which animals remain in frame. So does a detour around a camera carrying human scent. Log the camera-nights with the card so a thin card shows short deployment or few deer instead of a guess.
Over the coming two weeks, mark every deer as a pass or a look or a bolt. Also mark whether anyone walked in to that camera. If bolts cluster only after those walks, blame the walk. If bolts arrive on nights with no visit and the lamp is the shorter wavelength, move that camera back from the trail.
NOTES AND SOURCES
Fully Drawn Research is an independent data analysis desk, not affiliated with any state wildlife agency, transportation agency, mapping provider or outfitter. This guide reports published research and FDR's reading of it. It does not predict what game will do at any one stand or blind.
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