Do me a favor. Stand up and shaggy for me. You'll quickly see it's not a verb.
Have
The simple predicate in the given sentence is "have." It is a verb that shows the action or state of the subject, which in this case is "lion." To identify the simple predicate, focus on the verb that directly relates to the subject and ask yourself what the subject is doing or being. In this sentence, the lion "has" something, specifically "shaggy manes."