Scent is a mechanic in The Long Dark which increases the distance which predators can detect the survivor by smell. Scent is increased when the survivor is carrying meat and fresh guts, and is affected by wind speed, wind direction, and game difficulty experience. An approximation of current Scent is represented by the "Scent Meter."
The Scent Meter is a toggled element which approximates the survivor's current Scent amount; the more "Scent Marks" the survivor has (colored white), the higher the survivor's scent and radius they can be detected by predators. It can be viewed under Quick Stats (TAB key) or Status (F key).
Mechanics of Scent
Scent only affects predators (Wolves, Timberwolves, Poisoned Wolves, and Bear): attracting them to the player's general area, but not necessarily to their current location.
Bears have the most sensitive noses of any predator, and will travel over half the map in search of the player at higher scent levels, far outside of their normal patrol pathways.
The greater the Scent, the wider radius a predator can detect it. If unscented, predators can only detect the survivor by sight and sound.
Stacked Scented items (e.g. Fresh Guts, Cooked Meals) only count per-stack, not per item.
Item condition and weight has no affect on scent.
Predators only seek Bait they can see, but can detect Scented items when carried by the survivor regardless of terrain.
Wind Speed and Direction affects Scent distance, positively and negatively.
The Scent Meter shows three indicator icons but Scent does not follow actually hard breaking points. E.g. a piece of cooked meat will not yield one Scent Meter icon, but can still be detected by predators.
Meat/Meals can be mostly eaten by the survivor but still dropped as a decoy, by eating and aborting the action (ESC).
Survival Mode affects Scent significantly (Stalker as the highest, followed by Interloper/Voyageur, with Pilgrim as lowest). On harder modes it is beneficial to minimize carrying scented items, and to drop them as soon as possible (such as immediately upon harvesting/cooking).
Cooking meat/fish on-site reduces Scent during transit.
Crouching while manipulating Scent (picking up and dropping scented items) can be used to manipulate predators to specific locations, or to attack other wildlife.
Cat Tails and artificial foods are a scent-free way of traveling.