Many animals have ways to tell others to stay away when they are defending their food or protecting themselves. If they can convince an animal or person to keep its distance, then they may be able to avoid a fight.
This type of communication can be different for different kinds of animals. A bird may screech and dive at your head if it thinks you are too close to its nest. A dog may bark. A cat may hiss.
A camel will bring some of its stomach contents into its mouth, mix them with saliva, and spit them at you. That's a pretty clear signal to back off.