Yes they could. I sell them and they work on a gravity feed basis - as the dog eats or drinks more drops down so they get a constant supply. No good for Labs or other greedy dogs! Better for water than food. Not meant to be a substitute for being there to feed your dog, just to provide a regular supply.
I have one dog who would eat the whole lot in one go and the other one who only eats what she needs when she is hungry - so one would starve and the other would die from overeating!!