Over here in Hungary there is a general way of saying this:
'Kérjük, ne etesse az állatokat!' (Please don't feed the animals)

The first answer is no doubt correct.
However, if this sign was to be posted in Hungary, I would recommend:
"Az alligátorok etetése tilos!"
[feeding of alligators is prohibited]
The Hungarian version differs not only in the language itself but also in its style. It is a national tendency to have quite harsh warning signs rather than polite requests, orders instead of suggestions posted in Hungary.
I'm not saying the English is always polite, but the Hungarian tends to sound a lot more serious, even in less dangerous cases such as "Please keep off the grass" -- "Fűre lépni tilos!"