We delight and laugh at animals at doing funny things, but do they sometimes do them to make others laugh on purpose? Our closest relatives great apes, including orangutans, chimpanzees, bonobos, and gorillas, love practical jokes. Researchers say that this is proof that animals too have a sense of humor.

This isn't the first time scientists have suggested this. Charles Darwin, in his book The Descent of Man, wrote about dogs and their sense of humor. He proposed that we could interpret their playful teasing while playing fetch as them playing a practical joke on their owners. There is also research suggesting dogs engage in teasing behavior among themselves just like the great apes do. 

Equestrian Lynn Acton writes that horses definitely have a sense of humor. Although horses aren't generally big on disobedience, sometimes they break the rules if they see that it makes us laugh. They understand our emotional reactions, and, if they're encouraged, they might engage in silly behavior more often.

"The question has been raised as to whether these behaviors are true humor, that is, actions intended to amuse us? Or are they learned because they received positive responses in the past? I think a repeated behavior could be either one, but a novel behavior intended to elicit laughter sounds like real humor to me," Acton claims.

The reason why some researchers are skeptical about animals having a sense of humor is that it serves no evolutionary purpose. For humans, it's a bonding strategy. It's how we break the ice, find friends, and connect with our loved ones.

"We don't know if it's the same in apes or other animals, but it's possible. To know for sure, we would need to test and observe more groups of primates and other species," researcher Isabelle Laumer told The BBC. 

Perhaps not all animals have a sense of humor, but many sure like to have fun. Rats, for example, really like it when we tickle them. In 2023, researchers found that when tickled, rats squeak joyfully in a high-pitched noise, similar to a giggling sound. And they come back to get the tickles again and again: the researchers can even make them play hide and seek to get the "tickling reward."

The famous gorilla Koko, who knew over 1,000 American Sign Language signs and 2,000 spoken English words, demonstrated that she understood slapstick comedy. One time, she signed the word "chase" after tying her trainer's shoelaces together, and made laughing noises when he tripped.

Rats aren't the only ones who like tickling. Chimps, orangutans, and gorillas also respond to tickling with gargalesis–that's the scientific term of laughter tickle response. Great apes use "laughter" for similar reasons that humans do: as a means of social bonding and in light-hearted interactions between parents and children.

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.

So far, scientists have proved that around 65 species of animals engage in behaviors similar to laughter, and most do so during playful activities. Most of them are primates, but also include foxes, whales, and seals. Even cats made the list; the researchers classified their hissing as laughter.