Why did Buck trap some animals, only to let them go?

(The call of the wild)

Answer: When Buck was not hungry he would practice the skills he had learned by trapping the animals for the thrill and excitement of it and let them go or run away from him.

Explanation:

Buck usually did not kill for recklessness of it or cruelty nor for pleasure rather he killed only when he needed food for his preservation. Earlier When Buck was not hungry he would practice the skills he had learned by trapping the animals for the thrill and excitement of it and let them go or run away from him.