Monk Seal on Laysan Beach

Monk Seal on Laysan Beach. An adult monk seal is usually dark gray or brown with a light gray or yellow belly. Adults can weigh anywhere from 375 to 500 pounds; adult females are generally larger than males. Pups are jet black and usually weigh 25 to 30 pounds at birth and weigh up to 132 to 198 pounds within five to six weeks. Nihoa Millerbird Translocation. The monk seal's common name is derived from its folds of skin that look like a monk's hood, and because it spends most of its time alone or in very small groups.