Pagophilic behaviour: mother seal suckling pup on the ice

True seals of the Northwest Atlantic exhibit a variety of reproductive patterns associated with different breeding substrates. Terrestrial breeding species have relatively long lactation (24 days in harbor seals (Phoca vitulina)) whereas species that breed on pack ice have brief but intense lactation. For example, hooded seals (Cystophora cristata) have the briefest lactation known for any mammal: 4 days, but the milk is of high quality and the young spend a large part of the day nursing (after Perry et. al. 1995. J. Mammal 76:22)