Cultural differences explain behavior variations in captive gorillas

ST. LOUIS -- Captive gorillas actually are a cultured bunch.

Genetics or environment alone cannot explain variations in the behavior of different groups of the apes, a study found.

Behavioral surveys of the roughly 370 gorillas in U.S. zoos showed 48 variations in how individual groups of the apes make signals, use tools and seek comfort, said Tara Stoinski of Zoo Atlanta and the Dian Fossey Gorilla Fund International.

"What became very obvious is there is a very distinct pattern of similarities and differences between groups," Stoinski said.

That suggests the gorillas pass along the different traits socially, not genetically, which is a hallmark of culture. Results were presented Sunday at the annual meeting of the American Association for the Advancement of Science.

Researchers previously have found that other ape species -- including chimpanzees and orangutans -- show cultural differences as well in how they forage, use tools and court one another.

"These animals are smart enough to observe behaviors and imitate them," said Ingrid Porton, curator of primates at the Saint Louis Zoo.

That gorillas do the same and perhaps aren't the "slightly dumb cousins" of the ape family shouldn't be surprising, said Andrew Whiten, a professor of evolutionary and developmental psychology at the University of St. Andrews.

"It is quite surprising only if you take that common notion that gorillas aren't as smart as the rest," said Whiten, a chimp expert.

Stoinski said the surveys found that even gorillas at the same zoo but living in separate groups can display cultural differences. At Zoo Atlanta, only some gorilla groups use sticks to push aside the electrified wires that protect the trees in their enclosures, allowing the apes to snack on the bark without getting shocked, she said.

As for chimps, recent videos, described Sunday to reporters by Whiten, show the apes in the Congo using a "tool kit" to collect and eat termites.

The chimps first use a large stick to tunnel a foot deep into termite mounds. They then pull out the large stick and use a more slender piece of vegetation that they've frayed to fish out the insects through the shaft they've created, Whiten said.

Such examples of learned behaviors, when passed down from generation to generation, may have an influence on evolution, said Carel von Schaik, an orangutan expert at the University of Zurich.

"You can also argue that cultural species will become smarter species," von Schaik said.