zoo elephants spend 22% of their time engaged in unnatural behavior, such as moving their heads back and forth, and bears spend 30% of their time pacing in their cages.

spend + 시간 + ~ing 형태 아닌가요?
곰은 pacing 으로 ~ing 형태가 옳게 왔잖아요.
근데 뒤에 engaged 가 나온건 어떻게 해서 나오게 된 건가요?