When scientists write things like books, articles, or papers about animals, they have to give credit to other scientists who did research on similar things before them. And they do this by putting the other scientist's name and the year they did the research in parentheses, like this: (Smith, 1999).
This is called an author citation. It helps give credit to the scientists who did the research and also helps other scientists know where they can find more information about the topic they're studying. So if someone wants to learn more about what Smith wrote about in 1999, they can go find that book or article and read it too.
Author citation is very important in zoology because it helps keep track of all the different things that scientists have learned about animals over time. It's like a big library of information that all scientists can use to help learn more about the world around us!