Bears are animals of the family Ursidae, and are classified as dog-like carnivorans. They are particularly defensive quadrupedal predators, known to attack anything they perceive as a threat to themselves or their territory.
Behind the scenes
Journalists and playtesters covering Metal Gear Solid V: The Phantom Pain confirmed that the player could occasionally encounter bears during gameplay. They also confirmed that they could be captured, although they noted that it would take a lot of effort to do so, one of whom even admitted he got killed by one during his run. In real life, Afghanistan is home to both the Asiatic black bear (Ursus thibetanus) and the brown bear (Ursus arctos).  The Official PlayStation Magazine and Official Xbox Magazine later mentioned that one of the side missions for the game involved hunting a legendary bear.
The 2015 Gamescom demo for Mother Base and FOB confirmed that Brown Bears would appear in The Phantom Pain. Ocelot will tell Snake that it is "a myth" to play dead if encountering an aggressive bear will eventually leave a person alone. The bear which was a mission target was a Himalayan Brown Bear (Ursus arctos isabellinus), distinct from other bears by having lighter-colored fur.
In-game, the bears can be tranquilized with one shot (using the lowest-grade pistol) if caught by surprise and shot in the head. The bears will first attempt to intimidate the player, and will leave the player alone. They are not hard to hide from, as Snake can be within 20 meters of the bear without alerting the animal.