Rainforest Chimpanzees Dig Wells for Water in Fascinating, Rare Behavior

Chimpanzees living in a rainforest in Uganda have been observed to actively dig wells in the soil to find fresh water, according to a study published in the journal Primates this month.

This is the first time that well-digging has been observed in a group of chimpanzees living in the rainforest, and is an example of animals using intelligence and innovation to access hidden resources—while water is often available easily if collected in cavities and channels in rocks or trees, water in the rainforest is also often concealed beneath the surface of the soil.

According to co-author Cat Hobaiter, a primatologist at the University of St. Andrews, well-digging is usually only observed in groups of chimps that live in the savannah.

According to a study, for the first time, chimpanzees living in the Ugandan rainforest have been observed digging wells for water. Stock images: a chimpanzee with a baby on its back and someone drinking water from a well. iStock / Getty Images Plus

"Well digging is quite rare, so its appearance in a rainforest group was a surprise! But while the Waibira chimpanzees live in a rainforest—drinking water is so important that even if there are only one to two months where it's difficult to access, this is still a really important problem to solve," she told Newsweek.

The study's authors also said this behavior originated from one particular individual and subsequently spread amongst the rest of the group.

A young female who had immigrated to the Waibira rainforest community in 2014 was observed repeatedly digging wells in a stagnant water hole that was usually only used by the community as a last resort during the dry season. According to the paper, she dug small holes with her hands in the sandy-gravel substrate of the water hole, waited the approximately 13 seconds that it took for the water to filter through, then drank it.

Over time, the other chimps in the group observed this young female with "apparent interest." Eventually, the other individuals used her wells for both direct drinking and sponging up of water with tools made of leaves, moss, or a combination of both materials after she was done.

"It's taken time for others to learn the behavior, and so far it's only been females and young chimps that have picked it up," Hobaiter said. "Young chimps often learn new behavior more easily, and perhaps here the adult females are especially in need of hydration because they're often still producing milk for their young infants. So that might have been a strong motivator to learn this new trick for accessing good water."

"One of the most interesting things was seeing the other chimpanzees' responses to her digging—even large dominant males would politely wait for her to finish digging and drinking, and only then go and borrow her well, which is pretty unusual around such a valuable resource!"

The authors aren't sure whether this female invented the behavior herself, having figured out that water is concealed under the ground, or if she learned it from the community that she was originally born into.

"Well digging might seem a simple solution but it's actually a tricky one!" Hobaiter said. "The water is concealed—you can't tell it's there from looking at the ground. And even harder, once you start digging you still have to wait a little while for the water to rise up in the well. We know that behavior with delayed rewards is much more difficult to learn, so this is a really fascinating behavior to see."