研究表明大猩猩在拥挤的森林里变得更暴力

acquire – v. to get (something) : to come to own (something) : to come to have (something)

primatologist – n. an expert in the branch of zoology that deals with primates - any member of the group of animals that includes human beings, apes, and monkeys

habitat – n. the place or type of place where a plant or animal naturally or normally lives or grows

elder – adj. of greater age