Denizen

The Denizen of the Forest is an enemy added in Black Ops II, and only appears in the Green Run map. It only spawns in the fog between locations, and does not yield any points for being killed. Killing a Denizen does not drop a power up either.

Call of Duty: Black Ops II
The Denizens have low health, and can be killed before they leap on a player. Their health when leaping does scale with that of the Zombies, at the same rate. When attached, the Denizen takes five melees before it lets go, however it will be reduced to two hits with the Galvaknuckles or three with the Bowie knife. If a Denizen leaps on a player, they will inflict damage until killed. They can be killed be either another player shooting it or by hitting the melee button. A player with a Denizen mounted on them can still walk and evade zombies. Once jumped upon, the player will move slower, and Stamin-Up does not apply its effect.

Behaviour
If a player steps out into the fog between bus stops, a Denizen will emerge from the ground, and start shrieking. They do not have an infinite range to leap on a player, and will attempt to run after the player before getting in range to jump on them. It has been noted that a Denizen will run back into the dust if the player returns to the clear air around the bus stops. Denizens will not go after monkey bombs.

Achievements/Trophies
To get the achievement/trophy "Fuel Efficient", the player must first engage the power, then find a lamp post with a green light. Then find a Denizen, and have it leap on you. Walk under said lamp post, and it will detach from you, and dive into the ground, leaving a hole. The player can then utilize this to teleport to another green light lampost. Doing it once is sufficient to gain the achievement/trophy.

To gain the achievement/trophy "I don't think they exist", one must kill a Denizen that has latched onto themselves, via the melee button. Killing it before it latches or getting someone else to shoot it off will not gain this achievement/trophy.

Trivia

 * They share a facial resemblance to Richtofen.
 * On a side note, they resemble trolls, or Smeagle from the Lord of the Rings series