This can cost you precious time when you’re photographing an animal that may not be in the perfect spot for long.
Also, I strongly recommend that you do not manually set the ISO as well when you’re in manual mode. If you do, and all three settings are manual, you’ll need to do too much trial-and-error and fiddling with your camera settings constantly. This can cost you precious time when you’re photographing an animal that may not be in the perfect spot for long.