If you want to find the secrets of the universe, think in terms of energy, frequency and vibration - Nikola Tesla.
Many would scoff at the idea of inter species communication without the use of fancy and futuristic technology, but for many people crossing the boundaries of what is deemed to be normal and ordinary and communicating with other vessels of life- be it animals , plants or even landscapes is not such a far fetched dream!
Like Tesla rightfully said, if you want to understand how this works you need to tap into the subtle realms of your daily physical life. Let this be your re-introduction to your first language which is and has always been energy.
In short animal communication is very real and is possible through something called telepathy. We all have the innate ability to connect with another being's consciousness and while its not exactly reading someone's thoughts word to word, it is still much more common than you would think.
Think of scenarios where you could finish somebody's sentences before they had a chance to speak or a situation where you suddenly hum a song someone near you was thinking about. All of these small co-incidences are just you tuning into your psychic abilities.
This is the boot camp to exploring animal communication!