From tickling to playing catch, animals engage in certain behaviors just for fun, even enjoying sensations that are unknown to humans, concludes an extensive new survey on pleasure in the animal kingdom.
The findings, published in the latest Applied Animal Behavior Science, hold moral significance, argues author Jonathan Balcombe. He believes scientists, conservationists and other animal rights activists should not overlook animal joy.
"The capacity for pleasure means that an animal's life has intrinsic value, that is, value to the individual independent of his or her value to anyone else, including humans," Balcombe, a senior research scientist for the Physicians Committee for Responsible Medicine, explained to Discovery News.
He determined animals experience happiness for happiness' sake related to play, food, touch and sex. Observations of herring gulls in Virginia, for example, found these birds play "drop-catch," tossing clams and other small, hard objects as though they were baseballs, just for pure enjoyment.
In terms of food, green iguanas go to great lengths to find fresh, leafy lettuce, even when supplied with ample amounts of more nutritious reptile chow. Studies on other animals indicate some foods, independent of their nutrition levels, cause animals to release pleasure-producing opioids in their bodies. Language-trained apes and parrots have even told their owners they loved or hated certain edibles.
Pleasure itself can be the end-all reward, as "regardless of the evolutionary benefits of a behavior," he said, "animals often do things because they are rewarding."
10 peeks at sex in the wild"I doubt that a monkey thinks, 'If I eat this fig it will sustain me,' but rather, 'Ooh, yummy, a delicious fig!'" added Balcombe, whose book "Exultant Ark: A Pictorial Tour of Animal Pleasures" is scheduled for release next year.
Regarding touch, a human might go to a spa for a mud bath and massage, but nature creates its own "spas" for hippopotamuses at freshwater springs in Kenya. There, wallowing hippos gather, moving in and out of "cleaning stations" where multiple fish species congregate to nibble hippo parasites, loose skin, fungal growths and more.
The hippos "deliberately splay their toes, spread their legs and hold their mouths open," often becoming "so relaxed during these spa treatments that they would sometimes fall asleep," Balcombe recounted.
Sex isn't just for procreation, the paper further suggests.
"Oral sex that appears purely for pleasure has been documented in goats, hyenas, various primates, manatees, bats and sheep," said Balcombe, who added that homosexuality is practiced within at least 300 species. Masturbation, even among certain birds, has also been noted.
Animals also may experience pleasures that go beyond human senses. Electric fish seem to enjoy giving each other stimulating charges, for example, while dolphins use "low-pitched buzzing clicks" near their genital areas, which "appears to be a way of giving pleasure to another."
Martin Stephens, vice president of Animal Research Issues at The Humane Society of the United States, told Discovery News that discussions of animal pleasure are often left out of science, with the emphasis instead going to negative experiences, like pain and stress. The two extremes of the feeling spectrum shouldn't be mutually exclusive, however.
"Balcombe is right that depriving an animal of positive experience through captivity and killing is typically not factored into the cost/benefit assessments underlying the review of animal experiments," Stephens said, adding that many scientists undervalue positive experiences felt by animals as being "mere rewards" linked to evolutionary benefits.
While virtually all animals are pleasure seekers, Balcombe believes a few species miss out on fun.
He said, "The experience of pleasure requires some level of conscious awareness, so we may safely exclude sponges and jellyfish from the list."
© 2012 Discovery Channel