Reproductive

Breeding season is between June and August, with birth usually occurring between March and June. The average gestation time is nine months. Mothers of newborn pups are devoted to their offspring while nursing. For the first 5-to-6 to weeks of a newborn's life, the mother is so busy safely raising her pup that she will not eat. The pups go from 35 pounds at birth to roughly 175 pounds while being nursed. The mothers, though, will lose hundreds of pounds during this time. Once finished nursing her pups, the mothers will abandon their offspring and head out to the ocean to feed.

Monk seals are usually solitary, and although they will sometimes lie near each other in small groups they are careful not to touch each other, and may continually return to a particular beach. They spend most of their time at sea, about 2/3 of their time! They come to shore to rest (some will sleep for days on the beach in Hawaii), and to give birth. Females are sexually mature at 5-6 years, but it is unknown when males become sexually mature. Pregnancy lasts 9-11 months. Hawaiian monk seals give birth in March/April, and Mediterranean monk seals give birth in autumn – those for both species' pups have been observed year-round.