Animals are said to be gregarious when they are of the same species and move together in a group. This behavior can be seen in various animals, such as wildebeests, zebras, and birds.
There are different reasons why animals may exhibit gregarious behavior. One reason is for protection from predators. Being in a group makes it more difficult for a predator to target one individual. Animals in a group can also help defend against predators by displaying protective behaviors, such as giving an alarm to alert others when danger threatens.
Another reason for gregarious behavior is for mating purposes. Some animals may form groups during breeding season, where males compete for females and display their dominance.
So, the correct answer is "they are of the same species moving together in a group."