Gorillas eat walnuts.

Let me tell you something. I used to be a keeper of primates in Shanghai Zoo. Many kinds of primates have this condition, which is called rumination; I once asked an animal expert in Germany about this situation, and he said they didn't know the situation either. At present, there are two possibilities, one is that they are too boring, and the other is that they simply like to eat this kind of food (don't spray rice! )