Bear shatters glass at Minnesota zoo with rock: do grizzlies use tools?

A bear threw a rock at the glass pane separating it from visitors at the Minnesota Zoo Monday. Research suggests bears may be among the species that are capable of using tools.

A grizzly bear at the Minnesota Zoo caused a scene Monday morning when it threw a basketball-sized rock at the glass barrier separating the exhibit from the public.

The first of the glass pane’s five layers shattered but stayed in place “like a windshield”  as the bear repeatedly slammed the rock into it, zoo animal collections manager Tony Fisher told the Minneapolis Star Tribune.

The grizzly bear exhibit is temporarily closed while the zoo patches up the window and awaits a more permanent fix.

Mr. Fisher said he was unsure of which bear threw the rock, but suspects it was a nearly full-grown male named Kenai who is “usually the clown out there.” The Star Tribune reported that full-grown grizzlies can weigh in at 800-900 pounds.

“He didn’t know what he was doing,” Fisher said. “He was just being a bear.”

But recent research suggests Fisher may be wrong about that.

A Washington State University study completed last August revealed that bears may be as adept at using tools as primates, LiveScience reported.

In the study, bears were tested on the ability to turn boxes and tree stumps into step stools when attempting to grab a donut hanging just out of reach on a string. Out of the eight bears studied, the six born in captivity at WSU were quick to complete the task, while the two brought in from the wild struggled more.

Lynne Nelson, assistant director of the Washington State University Bear Research Education and Conservation Center, who oversaw the study, told LiveScience the research was inspired by a 2012 report of a bear using a rock to scratch its face.

"Those of us who work with bears looked at that and thought, 'Wow, that's newsworthy?'" she said.

LiveScience also reported that there have been accounts of polar bears throwing objects in zoos, suggesting Kenai’s outburst may not have been without precedent.

Robert Shumaker, co-author of "Animal Tool Behavior," told NPR in 2011 that outside of zoos, such behavior in wild polar bears has occasionally been documented as well.

"One of the stories we have is polar bears getting up on a cliff and hurling great chunks of ice down on something like a walrus to kill it," Mr. Shumaker said.

At the Minnesota Zoo, however, rocks and other objects bears could lift are supposed to be secure, according to the Star Tribune. After Monday’s mishap, Fisher said, “we’ll have to go back through the exhibit and anchor down anything they can lift.”

This report contains material from the Associated Press.