Forest Friendships

When chimps and gorillas meet, no chest-pounding is required.

In the misty forests the Congolese rainforest, a small band of apes fed in a tree. Adult chimpanzees dined on fruit in the canopy, while a pair of young apes played nearby. But one of the playing apes was not a chimpanzee : It was a gorilla.

'' Most of what we'd been told about the interactions between these two species is that they'd be competitive or they would avoid each other,'' said Crickette Sanz, an anthropologist at Washington University in St Louis who witnessed such a scene for the first time in 2000.

But during the decades of observations at Nouabale-Ndoki National Park in the Republic of Congo, she and her colleagues recorded yearslong relationships and other forms of social interactions between chimpanzees and gorillas.

The research was published last month in iScience.

Often, Dr. Sanz said, interactions occurred after a band of chimps located an exciting meal, such as a fruiting strangler fig or kapok. The sound of excited chimpanzees would draw in a family group of gorillas. In 34 percent of the encounters, the two ape bands went on to feed in the same tree or to forage alongside each other for different foods.

The interactions the team saw were ''generally tolerant,'' Dr. Sanz said, and occasionally actively friendly. Individuals paired off to chase one another, wrestle and generally roughhouse. These relationships tended to last for years, the team found. [ Asher Elbein ]


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