Some of us converse better than others not only with fellow humans but also with animals. As to animals, they speak their own language, and though we can interpret and use gestures, most of us don’t speak dog, cat, bird, horse, pig, dolphin and/or other animal languages. But we can and do talk to them and many understand many words.
Dogs: Studies have determined that dogs can learn an average of between 89 and 165 words, some, as many as 250. On a ranking system of words responded to by breed the top learner is the Border Collie possibly thanks to Rico, a highly trained Border Collie, who knows over 1000 words. Next in rank is the Poodle followed by the German Shepherd.
Cats: Supposedly cats understand around 20-40 words, maybe more. There is no really clear count because cats are notoriously sly in letting on just what they know. They do communicate back, on their own terms, with around 100 vocal variations that they do not use to interact with other cats.
Birds: Parrots are the most talkative. The African Gray parrot can learn and recite more than 1000 words and parakeets have a thing or two to say. I can understand when my chickens tell me they want treats or to get out into the garden especially where they are not allowed. They definitely know the word no though they don’t always cooperate. Their total count: 7? OK, maybe 5.
Pigs: Said to be the 4th smartest animal on earth, pigs are social beings with good memories and good manners. They understand, if not words, symbolic language, gestures and tone of voice, and have their own 20 distinct sounds ranging from oinks to grunts. (In rating the smartest animals on earth, because humans are doing the ranking, humans are #1 followed by dolphins, ravens. pigs, chimpanzees, elephants, African Gray parrots, octopuses, Bonobos, and rats, for the top 10.)
Aquatic animals: Evaluations and studies with dolphins show them responding to gestures and sounds (they are also very good at math) and there are many recordings of their own vocal communications within their community. Whales also communicate with each other and respond to some gestures. Octopuses are waiting with their 9 brains for humans to learn about their method of communicating.
Perhaps in time researchers will figure out how we humans can learn to communicate in new ways with other animal species using symbols, gestures, body language, voice tones, sounds and music to tune into and respond to what they are saying so we can have a dialogue.