Bear Power icons will bounce if they aren't passive powers and if a letter tile on the board has a lifetime counter of 1. The intent is that the bouncing will remind a player that activating the power might be a way of preventing a rock. (Of course you could also prevent the rock by simply using the letter to spell a word.)
Note that the code behind this bouncing is currently not very smart. E.g., the Break Rock Tile power will bounce when a 1-lifetime letter tile is on the board even though breaking a rock has nothing to do with whether the 1-lifetime letter tile will turn into a rock. The same power will also bounce even if there are no rocks on the board to break. Hopefully we can make this code smarter in the future.