You may think that dogs eat everything they see. Well wrong. One thing for sure that I know Cooper will not eat is mushrooms. Whenever someone drops a mushroom he will sniff it and back away. He doesn't do this because they don't taste good. I'm absolutely sure he does this because mushrooms that grow outside are poisonous, and it's his instinct not to EAT MUSHROOMS!! This is proof that not all dogs eat everything they see.
( Once again I tested this theory out. While my mom was cooking with mushrooms, I threw a piece of mushroom on the ground to see if he would eat it. Immediately Cooper came over. At first all he did was sniff it. Then, he picked it up and started playing with it. Throwing, catching, running, but no eating.)