What did the Monkey say to her boyfriend?
“You’re my prime mate!”
Why is it funny (if it is funny)?
A “primate” is the scientific word for a monkey (or an ape, including human apes!). The word “prime” means “first” or “best.” The word “mate” means “one member of an animal couple,” and in British slang, it means “friend.” So, this monkey is being very romantic, calling her boyfriend her best friend and companion, as well as a monkey, which he clearly is.