Snake side quest locations.
The snakes will attempt to run away when you get close to them and burrow into the ground, use Strife to shoot them.
The first 2 snakes are on the right, down in the water. 1 is sitting in front of a chest, the other is directly north of it.
The 2 snakes near the zone-map collectable usually start running away before you actually see them, in the direction of the arrow, ignore the skeleton enemies and rush the snakes.
The final 3 snakes are behind the waterfall.