These slugs excrete a slimy substance to keep themselves hydrated. A naturalist at Muir Woods told us that most animals will not eat banana slugs due to the slime they produce on their skin, but raccoons have found they can wash off the slime in water and then dine on these delicacies. The slime evidently turns into an incredible glue according to those who have gotten it on their hands, so I would recommend letting these creatures be.
As lowly as the banana slug may seem, it does get respect on one college campus. Most colleges and universities here in the U.S. pick a mascot that is strong or fierce, like a lion or bear or Trojan, but the University of California at Santa Cruz chose the banana slug. Why? I suppose they have their reasons.