The Zebra Stalker is the common form of the Gray Stalker which appears earlier in the game. They typically attack in small groups and the others don't seem to spawn until Aya gets near them or another has been killed. When they are cloaked, they cannot be targeted but running near them will cause them to attack, which can be avoided, also causing them to become visible. They aren't too dangerous and group attacks like Combustion or shotgun shells do good against them, although the latter isn't the optimal choice. Overall they aren't too dangerous compared to the other Stalkers.