Zoo keepers, park wardens and such stalwart custodians clearly have their patience taxed repeatedly by people who are just plain ignorant and utterly stupid - hence these public warning signs. Some are just friendly reminders to keep an eye on children, but you’ve got to wonder why anyone would want to sit on a crocodile. Obviously people do, and they expect to live!
One Canadian sign shows that humor works wonders when reminding dog owners to clean up after their pets. In another case, the banana slug crossing sign coupled with the slippery one make for a perfect cautionary pairing.