for approximately six weeks, they grow considerably, eventually weighing between by the time they are weaned, while the mother loses up to . Monk seals, like elephant seals, shed their hair and the outer layer of their skin in an annual catastrophic molt. During the most active period of the molt, about 10 days for the Hawaiian monk seal, the seal remains on the beach. The hair, generally dark gray on the dorsal side and lighter silver ventrally, gradually changes color through the year with exposure to atmospheric conditions. Sunlight and seawater cause the dark gray to become brown and the light silver to become yellow-brown, while long periods of time spent in the water can also promote algae growth, giving many seals a green tinge. The juvenile coat of the monk seal, manifest in a molt by the time a pup is weaned is silver-gray; pups are born with black pelage. Many Hawaiian monk seals sport scars from shark attacks or entanglements with fishing gear. Maximum life expectancy is 25 to 30 years. Evolution and migration The monk seals are members of the Phocidae. In an influential 1977 paper, Repenning and Ray proposed, based on certain unspecialized features, that they were the most primitive living seals. However, this idea has since been entirely superseded. In an effort to inform the public and conserve the seals, the National Oceanic Atmospheric Administration (NOAA) Fisheries Service developed a historical timeline to demonstrate that the Hawaiian islands has been home to the seals for millions of years and that the seals belong there. Evidence points to monk seals migrating to Hawaii between 4–11 million years ago (mya) through an open water passage between North and South America called the Central American Seaway. The Isthmus of Panama closed the Seaway approximately 3 million years ago. Berta and Sumich ask how this species came to the Hawaiian Islands when its closest relatives are on the other side of the world in the North Atlantic and Mediterranean Sea. The species may have evolved in the Pacific or Atlantic, but in either case, came to Hawaii long before the first Polynesians. Ecology Habitat The majority of the Hawaiian monk seal population can be found around the Northwest Hawaiian Islands but a small and growing population lives around the main Hawaiian Islands. These seals spend two-thirds of their time at sea. Monk seals spend much of their time