Brown Bear Tool Kit: A Rock for Scratching

In July 2010, a brown bear had an itch. To scratch it, he picked up a barnacle-covered rock and rubbed it over his muzzle.

Volker Deecke, a researcher at the University of Cumbria in the United Kingdom, happened to be watching at the edge of Glacier Bay, in Alaska, when he observed this, the first known example of tool use by a brown bear.

"The bear started picking up rocks from the seafloor and manipulating them with his hands and eventually just scratching his face using this rock," Deecke told Livescience.

While brown bears (Ursus arctos) have been observed using trees and boulders to scratch parts of their bodies, picking up a rock and using it as a tool to scratch takes a different thought process. "That boulder remains, physically speaking, part of the environment," Deecke said. "To use a tool like this [rock], the animal needs to have the ability to extend the boundaries of its body."

Apparently brown bears are able to wrap their minds around this idea, Deecke said, adding, "that's something that we just didn't know about bears."

A bear's story

Deecke was in Alaska in the summer of 2010 for an unrelated project — he actually studies whales, not bears — when locals told him about an old whale carcass that had washed up on the bank of the West arm of Glacier Bay, which would be a good place to watch for bears. [Gallery: Swimming Polar Bears]

Two young adult bears were playing on the beach and eating the rotting whale carcass for about an hour as Deecke watched. After a while, one of the bears went into the water to play and started digging around on the seafloor. He brought a rock up, positioned it in his hands and rubbed it on his face. In images Deecke took, he was able to see the rock was covered in barnacles.

This wild bear, which had never been in captivity or around humans, was performing this tool-use grooming behavior completely unprompted. He repeated the rock scratching three times, with three different barnacle-covered rocks.

Animal tool use

Tool use is common in primates and several species of fish use tools, and many birds and invertebrates too, but only a few examples are known from non-primate mammals. Sea otters use rocks to get at the meaty goodness inside clams and urchins. Elephants use branches they've plucked to swat flies from parts of their body they can't reach.

Since this is only a single example of bear tool use, researchers don't know how frequent or widespread it is. More research is needed to figure out how smart brown bears actually are, and how they match up with other animals, particularly other mammals.

"There's a real need to do more systematic research on their behavior and bear cognition in particular," Deecke said. "There's more going on with these animals than I think we are aware of right now."

The study was published Feb. 25 in the journal Animal Cognition.

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