Yes and no. I does detect if an animal walks into the area of the motion detector. It emits a multiple-second squirt of water. The noise, and getting hit by the stream of water, surprises the animal and sends it running...the first or second time. In my limited experience, a habitual user (squirrel, dog, cat-no experience with deer) will learn to go around the outer perimeter of the covered area or just move to another part of the yard. In my own situation, moving the scarer around to try to keep the critters guessing was not effective because of mature trees that provided a barrier to the stream of water. I'd still try one though. Your conditions may allow you to set up your target area more effectively.