Grass eating animals or ruminants have developed the habit of rumination. It is for reasons: one is 'cellulose present in the plants takes a long time to digest'. What are the other reasons?
Yes, this was also developed to protect them from predators
Grass-eating animals quickly swallow the grass and store it in a part of the stomach called rumen. This was developed also as a preventive method to protect themselves against predators. For example: deer can finish eating by swallowing the food quickly and run. This reduces the chances of being caught by their predators like lions and tigers because predators usually attack while herbivores are feeding.