emotional responses are deeply evolutionarily advantageous in any animals that are making complex decisions and behaviors (in many vertebrates, say) because they act as a reinforcer for a behavior. a bird taking a vigorous bath in a puddle is probably happy because if that behavior didnt elicit a positive feeling they wouldn't do it (it is dangerous to be on the ground and wet!). if an animal can feel fear, which i think is a less contested assertion to make, then it can certainly feel the opposite, that is, happy.

















