You can refer to the person who has captured a person or animal as their captor .
例句
They did not know what their captors planned for them.他們不知道抓他們的人打算拿他們怎么辦。
英漢詞典釋義
n.
捕捉者;捕獲者
The hostages were well treated by their captors.那些人質受到劫持者的善待。He cleverly tricked his captors.他巧妙地哄騙了捕捉他的人。The philosophy of them during their worst sufferings impressed even their captors.他們在最困苦時仍處之泰然,連捉住他們的人都深有感觸。
英英詞典釋義
Noun
1. a person who captures and holds people or animals