HELENA, Mont. - The grainy footage shows two grizzly bear cubs under the watchful eye of their mother as they romp through a field and playfully tease a nearby wolf.

The remarkable scene was captured by the U.S. Geological Survey as part of a research project into the bear population in northwestern Montana. It's one of several intriguing clips recently posted on the agency's Web site that depict life inside Glacier National Park - from a bear rubbing its backside on a tree to a wolf feeding on an elk carcass.

The five-minute video of the bear cubs shows the wolf drawing close several times. At one point, a cub takes a playful swat at the wolf. Other times, the mother bear makes her presence known and "bluff charges" the wolf, stopping short of an attack.

Although seemingly playful, the underlying forces of nature are clear.

"I have no doubt that if the mom was not there and the wolf had the opportunity, it would eat the cub," said USGS research biologist Kate Kendall, in a telephone interview Wednesday.

The video was shot Aug. 10 by an unmanned, sensor-activated camera positioned for Kendall's research. The grizzlies and wolf apparently were drawn to the area by an elk carcass.

Kendall said the adult bear was relatively small, perhaps 150 to 200 pounds. A typical sow in Glacier National park in August weighs about 250 pounds, she said.

"Maybe that's why the wolf was not as impressed" by the bear defense and kept returning, Kendall said.

There was no indication the bears or the wolf were injured during the encounter.

Fatal wolf attacks on bear cubs have been documented, according to Carolyn Sime, gray wolf coordinator for the Montana Department of Fish, Wildlife and Parks. However, she knew of no instance in which a wolf has killed an adult grizzly bear.

http://nrmsc.usgs.gov/news/KendallRemoteCamera.htm]]->