What do animals use their appendix for?
In some animals, like humans, the jury is still out as to what function an appendix serves. Humans can live without any complications if they appendix is removed. In animals such as rabbits, the appendix serves as a storage are for lymphatic tissue.
No it is not. The appendix is used to house anaerobic bacteria that assist in the breakdown of cellulose from plant material. In humans, the appendix is considered to be a vestigial organ which serves no useful purpose due to its small size, but the appendix is vital to many other animals with a primarily vegetarian diet.