If the shutter speed gets into dangerously slow territory, just bump up the ISO, and you’ll be good.
You may wonder, “If I want to prioritize a fast shutter speed, why not shoot shutter speed priority?” The answer is that aperture priority speeds up the process. In low light conditions, you simply set the widest aperture on your lens – something like f/2.8, f/4, or f/5.6 on most wildlife photography lenses – and pay careful attention to where your camera is floating the shutter speed. If the shutter speed gets into dangerously slow territory, just bump up the ISO, and you’ll be good.