Mammals and birds quickly learn to associate related stimuli or events. Associative learning includes classical (or Pavlovian) conditioning and operant conditioning, as well as simpler forms of learning, such as habituation.
Camera-trap an area over time and there is a good chance your subjects will make an association between the camera and the olfactory and visual stimuli you leave behind.
If you thought your camera trapping shenanigans in the woods were unnoticed, guess again. Chances are local wildlife knows the camera is there, and they are not afraid of it.
You will fool them more often if you set your cams in new areas where the residents have never encountered you and your equipment.
The regulars who appear in your pictures may not know who or what you are, but in their universe or Umwelt you are a distinct blend of stimuli.
Why? Because you smell, and so does your camera, which also flashes and makes sounds.
Whenever you venture into the field, you inadvertently scent mark your path and equipment.
Unless you take extreme measures. Then you can reduce your scent by washing with unscented soap, wearing clean clothes, and masking your scent.
The best way to mask scent is to thrash your body like a Finlander in the sauna. No need to strip down or surround yourself with svelte blonds, just beat yourself with aromatic plants like bay or sage until you smell like trampled plants.
The new carbon-impregnated clothes on the market may help to absorb some of your smells before they give you away.
Or you can spray yourself with Stumpy’s root juice.
But generally speaking, odor prophylaxis can be rather tedious, and scent-cleansing rituals will not render you smell-anonymous.
If you use scent lures or bait, like road kill, you reward the animal to tolerate the proximity of the camera.
Everything about the scent lure reaction -- from intensive sniffing, to slobbering, rubbing and rolling in the scent, as well as evacuating the bladder and bowel -- indicates they find it highly compelling and meaningful.
The camera becomes an accessory to pleasure.
I have a hunch – let’s call it a hypothesis -- that when resident animals cross your scent trail they may search for your camera, because food and scent have repeatedly reinforced tracking your scent trail.
Your scent is a cue to seek the reward of “good smells and eats”.
I believe this is more likely in species have relatively small home ranges, because the probability of camera encounters is relatively high. We’re talking here about wood rats, gray foxes, skunks, opossums, and racooons.
On the other hand, baits and scents may be less habit forming in far-ranging species like mountain lions, wolverines, fishers, bobcats, and coyotes.
It takes more time for them to make their rounds in their larger home ranges. Positive reinforcement will not occur until the animals have been repeatedly rewarded.
In support of this idea I would point to the tigers in Nepal’s Chitawan National Park.
Though they killed tethered buffaloes at a bait site near Tiger Tops Jungle Lodge, radio-tracking showed that they ranged as far and wide as other tigers in adjacent home ranges. In other words, they maintained their usual beat in search of prey. Some cats however became habitual bait visitors.
Okay, I've slipped from animal psychology to arm chair theorizing. Now someone needs to collect the data.