While the mother seal is on the beach only four to five weeks, she also loses about one-third of her body mass as she gives birth and nurses a pup to over 300 pounds while also nourishing herself with her metabolized blubber. Indeed, while the weight of the new born pup as a fraction of the mothers weight is similar to that for humans, at the end of four weeks the pup weighs about one-third as much as the mother, a ratio that doesn't happen with human babies for several years. ( http://www.elephantseal.org )