Wider lenses can go as small as f-stop 2 or even lower.
The best aperture for wildlife photography is a wide one (a small f-stop number). The lowest f-stop number will depend on your lens. We tend to stick to between f/3.5-5 on our wide lens and f/5-6 on our long zoom lens (the widest settings for each lens). Wider lenses can go as small as f-stop 2 or even lower.