Plenty of nonhuman animals have revealed their interesting ___(16)___ skills to curious scientists. Dolphins converse via an elaborate system of clicks and whistles, have signature whistles that act like names, and can remember old friends' "names" decades after first encountering them. Many great apes communicate by gaze, body language, ___(17)___ and even scent. Ravens gesticulate with their beaks and wings. And elephants gesture with their tusks. [The 5 Smartest Non-Primates on the Planet]
Most studies in animals, however, ___(18)___ the creatures communicate like humans via body language and gaze. Researchers also assumed that animals with eyes on the sides of their heads, such as horses, didn't use gaze to communicate.
But horses are ___(19)___ animals that constantly need to communicate with each other, whether to alert group mates to the presence of a/ an ___(20)___ or to share news of a tasty food source.