Thor, left, and Boo, two of three orphaned grizzly bear cubs that came to the Detroit Zoo in Royal Oak, Mich., from Alaska in December are seen, Thursday, March 22, 2012. The cubs spent the winter "denned up" as they would in the wild. The 14-month-old brothers explored their new habitat, including having a dip in the 6-foot-deep pool and doing a little rough-housing. The three were orphaned in October and captured by the Alaska Department of Fish and Game after their mother was shot and killed by a poacher. CARLOS OSORIO / AP PHOTO