The whole essence of language is communication. To communicate, one must be fluent in the means of communication.
While it might be difficult to say one can communicate in all known languages on earth. With humans generally, it's easier as compared to animals.
How can one communicate with animals other than using sign languages. It can be argued that some animals can be trained to understand communication but they cannot talk back only respond.
It is therefore good to note that communication is a two way thing and animals do not have the capacity to talk to humans.