Pagophilic ("ice-loving") nursing in phocid seals

"Terrestrial breeding seals have relatively long lactation, whereas seals that breed on pack ice have brief but intense lactation (as little as 4 days).Typically, patterns of lactation have been explained in adaptive terms. Those species that give birth on stable substrates have extended lactation, while those that give birth on unstable pack ice have briefer lactation that permits pups to achieve nutritional independence before the ice shifts or melts." (after Perry et al. 1995. J. Mammal. 76:22)