Polar bears will track down seal holes and wait by them until the seals rise out of them to breathe and then attack. This is also known as still hunting.
"Ahu" are stone platforms on which many moai sit. There are 313 known ahu and 125 of these carry moai. The biggest, Ahu Tongariki is 220 m (720 ft), and had the most (15) and tallest moai.