A group of antelope leaving the herd in search of better grassland is an example of

emigration

Explanation:

The emigration of an animal, in this case of the antelope, is the cause of the lack of food.

The animals are in constant search of food and better places to cohabitate. Antelope is leaving its herd to find a better place for food and even if it sounds strange, animals are also behaving as individuals in case there is threatening of hunger.

voluntary muscles are controlled by the cerebellum.