Demi the Cougar

 is a rare animal found in Red Dead Redemption. She can only be found in the Liars And Cheats DLC while playing in Free Roam on the Silent Hill hunting ground. She appears after all waves of cougars have been killed and is usually accompanied by two-five regular cougars. You can't find her in single player mode.

Characteristics
Demi can take a large amount of damage, even from high powered weapons like the Semi-auto Shotgun or the Buffalo Rifle. It is advised to stock up on ammo before attempting the Silent Hill hunting grounds.

Trivia

 * If the player goes onto the roof or inside of the shack in the centre of the hunting grounds, the cougars, excluding Demi, who is by far more powerful, cannot reach them.