The photo shows a sign that reads "DİKKAT KEDİ VAR KÖPEKLERİNİZİ KORUYUNUZ". This translates to "WARNING CAT PRESENT PROTECT YOUR DOGS". The joke is that cats are known to be predators of dogs. The sign is a humorous way to warn people about the presence of a cat and its potential danger to their dogs. It plays on the common stereotype of cats being mischievous and dogs being afraid of cats. The sign is likely placed in a place where people are likely to walk their dogs, such as a park or a street.