It was just the students trying to be their anti-establishment selves. When the university first opened the student body was asked to vote on name for the mascot, and they chose banana slugs. Those little beasts are found in the woods around Santa Cruz, and UC Santa Cruz is known as the “party school” in the (otherwise demanding) University of California network. But mostly they chose it because everybody who hears it says “Ewwwwww”. I’ve been known to scream when I encountered one on a trail — more than once.