The USGS runs a research project where they've put sensor-activated remote-controlled cameras in Glacier National Park.
Go to the page and you can see videos of bear cubs fighting wolves and dancing bears. No, it's got nothing to do with the Grateful Dead or Russian music or the circus. Just bears doing their tree rub thing, which makes it looks like they're dancing.
Try watching it and not smiling. But heed the warning at the end...don't dance with the bears.