Whalers hunted them extensively, and due to their slow traveling speed and well-known migratory route they were easily found in numbers. The discovery of their breeding lagoons in Mexico further hastened their decline. At one time there were 15 on-land stations in California alone for the processing of Gray Whales. Whale oil was very important at that time for use in lamps and in lubricating machinery. Since then it has come under the further protection of the Marine Mammal Act, the Endangered Species Act, and other federal and international protection treaties.
Gray whales mate one year and give birth the next.
Calves are usually born in the warm, shallow lagoons of Baja California, between December and April. Calves average 15 feet long at birth and weigh an estimated 1500 pounds. Nourished by approximately 50 gallons of the mother's rich milk each day, calves may gain 60 to 70 pounds daily and reach 18 to 19 feet in length by the end of winter. They are soon followed by the males, who continue courtship, and by juveniles of previous years. Mothers and new calves are the last to leave, occasionally remaining as late as May or June.