hunters who sometimes drive them several hundred yards inland to harvesting sites. The term fur seal comes from the thick waterproof underfur which numbers over 350,000 hairs per square inch (60,000/cm²). When seal skins are processed, the longer guard hairs are removed to reveal this underfur which is then straightened and dyed to make a very soft and warm pelt. Northern fur seals are found on both sides of the Pacific Ocean from about 32° north to the central Bering Sea. It is the most common species of fur seal which occurs in northern waters. Eight other species of fur seals have been described, most from the southern hemisphere.

General description: There is no pattern of rings or spots on the pelage of fur seals. Females and young males appear uniformly black when wet. They appear gray or brown when dry except for the lighter colored throat and chest areas which may be seen when an animal is viewed from the front. Mature bulls are predominantly brownish-black and begin developing a lighter colored mane around 6 years of age. Females that have been ashore for a few days may appear brown due to staining of the fur by mud and excrement. When observed at sea, fur seals appear very dark and are often seen porpoising or resting on the surface with one or more of their long flippers curved above the water.

Fully mature male northern fur seals weigh 450-600 pounds (200-275 kg) when they arrive at rookery areas in the late spring. As much as 25 percent of this weight may be lost during their stay on land. Mature females usually weigh 90-110 pounds (40-50 kg).

Life history: Alaska's Pribilof Islands provide breeding grounds for over two-thirds of the world population of northern fur seals. Hundreds of thousands of these animals return there each summer to give birth and breed. Large males arrive first, establishing territories in May and early June which they aggressively defend for an average of 50 days. As many as 100 females may eventually collect within each of these territories, although numbers of 20-60 are more common. Pregnant females begin arriving in early to mid-June. Within 48 hours after arrival they give birth to a single 10-14 pound (4.5-6.4 kg) pup and then mate again within a week. Females nurse their pups for three to four months, making several week-long trips to sea to feed during this period.

Female fur seals mature at 3 to 5 years of age, and over 80 percent of those between ages 8 and 13 are pregnant each year. Tagged females have lived for as long as 26 years, and one was found to still be reproductive at age 25. Males are sexually mature at 5 or 6 years but are usually not large enough or socially mature enough to enter the reproductive population until 9 or 10 years old. Males older than age 17 have not been found.

Migration and distribution: Seals begin leaving the Pribilof Islands in November. By late December virtually no animals will be seen ashore. Unless sick or injured, northern fur seals will rarely touch land again until the following summer when the cycle begins anew. Throughout the intervening months they occur most frequently near the continental shelf edge, usually not closer than 10 miles (16 km) nor further than 100 miles (160 km) from shore. Females and immature males (ages 1-5 years) swim to the south and may be found from Southeast Alaska to California with some going as far as the California-Mexico border. Adult males do not undertake an equivalent migration. It is generally thought that nearly all of the older males winter in the Gulf of Alaska and southern Bering Sea.