Hunting Towers are wooden structures that can be climbed. They give you a better overview over the area and make you harder to detect for the animals. Hunting Towers are nearly always on or near a big clearing.
Using Hunting Towers
You can climb up and down hunting towers if you are near the ladder. An icon will appear in the bottom right of your screen. Simply use the climb button (default: Space) to climb up or down. Currently you can only shoot from a hunting tower while standing. This makes it hard to get good long range shots. If an animal is approaching from the back side of the tower you can shoot from a prone position out of the opening at the ladder.
Hunting Towers on Whitehart Island
There are 17 hunting towers on Whitehart Island: