Interestingly, dogs have their own way of laughing, too. While they don't giggle or go "Ha-ha" like us, they "laugh" through their forceful panting. Behaviorists call this "play pant" and say that dogs use it when they're inviting humans or other dogs to play. Apparently, it sounds something like "hhuh-hhuh."
Researchers say that some birds make sounds similar to laughter. The kea parrots in New Zealand would interpret the warbling laughter of another kea as an invitation to play. When the researchers would play the laughter through speakers, the keas "would spontaneously start playing."
Dolphins can "smile" as well. When playing, they exhibit similar facial expressions to that of a smile. Researchers call it "open mouth display" which they only exhibit when socializing and engaging in play with other dolphins. Swedish researchers also found that dolphins "laugh." The noise that they make is a short burst of pulses followed by a whistle, and they only use it to indicate that a situation is pleasant or non-threatening.
