The Grey Seal generally breeds in Irish waters from September to December, and fluffy seal pups are born during the coldest months of the year. The cold, however, is not really a problem for them – why not? Their fluffy coat helps keep the pups warm till they have built up enough fat from the rich milk they suckle on. Their ability to gain fat is remarkable: grey seal pups triple their body mass in only three weeks. All that fat gets stored as blubber under their skin. With this experiment, you will feel for yourself the insulating power of fat!