In 2005, three works of art by a relatively unknown artist sold for more than $25,000 at an elite auction house in London. That’s not a huge amount as art sales go, but it made headlines because the painter was hardly typical. The artist was an ape, and the amount was the largest ever paid for art by a nonhuman.

Zoos have since taken note. Art by animals sells.

Yes, that preposition is correct — art “by,” not “about,” animals. This unlikely yet widespread practice generates a modest ongoing source of income in U.S. zoos, dependent on paintings made by gorillas, elephants, sea lions, birds and even stingrays and snakes, all sold in zoo gift shops and online. There is even a wider transnational market for art made by animals, with dolphins painting in Lithuania, elephants painting in Thailand, and primates painting in Australia.

This phenomenon raises several intriguing questions: Are animals really artists? Do captive animals want to paint? Should you invest your savings in seal squiggles? And how in the world would you teach a gorilla to paint anyway?

Paintings by animals surged into the public imagination when the prominent British ethologist Desmond Morris featured Congo the chimpanzee on his television show “Zoo Time” in the 1950s. Congo, sitting in a high chair and grasping a paint brush, appeared to enjoy making marks on paper with tempera paint, and some of the abstract images were quite arresting. It was Congo’s works that U.S. collector Howard Hong paid thousands for in 2005.

Howard Rutkowski, the auction house’s modern art curator, was shocked: “We had no idea what these things were worth,” he said. “We just put them [on sale] for our own amusement.”

Congo was not the first primate to paint, just the first to become so famous for doing so. And his sweeping brushmarks sold in part because his timing was right: In the 1950s, the U.S. and European art worlds were just embracing the post-World War II gestural works of abstract expressionist painters like Robert Motherwell.

Scientific studies on primate painting before and since have explored whether the origin of human art could be traced to our evolutionary histories. Biological anthropologist Anne Zeller, for example, has compared hundreds of young children’s’ drawings to those by apes to see if there is an evolutionary developmental link. Both human and nonhuman primates, she concludes, make highly intentional color and spatial choices. Perhaps these ways of making marks are linked to animals’ sense of communication, even if it is not clear to us humans.

But art-making is a social and cultural practice, with specific histories. Evolutionary questions, while provocative, can take us only so far, and they certainly don’t explain the popularity of painting by animals today. In modern zoos, many captive animals paint as part of “enrichment activities,” whether or not their creations catapult them to fame.

Enrichment activities are designed by animal caretakers in zoos, sanctuaries and even research labs to help provide stimulation in a captive environment where daily routines vary little. Puzzle feeders that require an animal to solve a problem to obtain a treat are a great example. Painting has the added benefit of providing one-on-one interaction time with the keeper who trains the animal through positive reinforcement. Whether to paint is always the animal’s choice, zookeepers explained to me. Some primates have been known to actively choose painting from among a number of offered enrichment activities — indicating, we can assume, that they regard it as pleasurable in some sense.

I observed this type of training “backstage” in the off-exhibit areas at the Oklahoma City Zoo and Botanical Garden, where gorillas like Gracie and her silverback father, Tatu, were being taught to paint by primate keeper Jennifer Davis. First, a gorilla is offered a brush and taught (or enticed), through praise and the reward of a tasty morsel, to give it back to the keeper, passing it through the wire mesh that separates them. This is more difficult than it sounds, because sometimes the gorilla wants to keep the brush to chew on.

Next, she is taught to touch the brush to a piece of paper held by the keeper on the other side of the mesh — this is called “targeting,” and it was the step Gracie was on after two months of training, when I observed. Each successful touch evokes praise, encouraging the gorilla to repeat it. Eventually the brush is loaded with nontoxic paint, so that as the gorilla passes it back to the keeper, the paint hits the paper and makes a mark. As the marks accumulate, a “painting” emerges.

But while the products get called gorilla paintings, they’re really a cross-species collaboration. Usually the caretaker selects the colors, manipulates the paper so that the brushstrokes fill the page instead of smearing into muddiness, and decides when the piece is done. Occasionally, the publicity department even gets into the act, deciding what color schemes will sell best. Occasionally, the animal selects the colors, as does Toba the Orangutan at the Oklahoma City Zoo, and sometimes the animal refuses — despite entreaties — to add another stroke, as Congo reportedly did. Yet despite this control, paintings by animals are always an ironic reminder of their captivity, because no animal paints in the wild.

These paintings are often sold in gift shops, with the proceeds going back to the primate division. The fundraising angle has been taken up not only by zoos nationwide, but also by sanctuaries like Florida’s Jungle Friends Primate Sanctuary, which provides a home for rescued monkeys and those retired from animal research, and even by local animal shelters as part of their fundraising events.

Prices for the pieces vary: Paintings by cheetahs, penguins and other species at the St. Louis Zoo go for up to $100 each; Houston Zoo animal paintings command $250 each. But the revenue can be significant. Paintings by brush-wielding seals at the Virginia Aquarium, for example, generated $15,000 in less than two years from gift shop sales in 2007. For a nonprofit organization, every thousand dollars counts, and art by animals can be an important source of income.

But are animals really “artists?” And is this really “art?” That depends on your definition.  If art is in the eye of the beholder, then Congo’s sweeping blazes of color can rival those of Jackson Pollock. If your notion of art is an exterior expression of an inner self, then maybe Chandra the Oklahoma City Zoo elephant’s paintings reveal less about her subjectivity than, say, how she might communicate through sounds and movement as the matriarch of a group of elephants in the wild.

But for primates such as Washoe, a chimpanzee who was raised like a human child by American scientists and died in 2007, the case may be different. Like Washoe, a few other primates have lived bicultural lives in human worlds as the subjects of language and cognition research, and can “talk” to us through signs and symbols. We may see something different in their creations, especially when they can title them themselves.

In the meantime, if you really want your pup to paint, you too can purchase the Pup-Casso painting set of nontoxic “finger” — paw — paints and have a go at getting her to walk across the canvas (the maker also sells a Kitty-Casso product).  It’ll look great on the refrigerator and your pet probably won’t mind, especially if the activity includes some treats at the end of the session.

Jane Desmond is an anthropologist at the University of Illinois at Urbana-Champaign and the author of “Displaying Death/Animating Life: Human-Animal Relations in Art, Science and Everyday Life.”

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