Yes they do both. At least females do. They dig out snow caves and 'hibernate' while their young grow. They don't have a drop in body temperature and heart rate like true hybernating bears, but they don't leave until their cubs are old enough, and even then will return to the den on occasion. Enough national geographic stuff though. I'm sure these bears aren't normal polar bears, but it's something to keep in mind that it's not totally out of their range of natural behaviors in their natural habitat. On a tropical island though...I don't doubt that they are a bit confused.

Maybe the caves are just cooler and with all of that fur and humidity who wouldn't long for a dark damp cave to cool off in.