Gray whales are so named for their color. They can reach upwards of 45 feet long, and a mature whale can weigh as much as 40 tons. They have two blowholes on top of their head and lack a dorsal fin. Their tails can be as long as 10-12 feet and are deeply notched at the center.
There are two populations of Gray whales that are known to exist: one in the Eastern Pacific Ocean (between the waters off the coast of Alaska and the Californian Big Sur) and one in the Western Pacific Ocean, whose migratory route is believed to be between the Sea of Okhotsk and South Korea. The latter population is much smaller (numbered around 130 individuals) than that of the Eastern Pacific Ocean's population, which is believed to be between 20,000 and 22,000 individuals.
Gray whales typically feed in one location and then migrate a distance of about 12,000 miles to their breeding grounds. This distance is believed to be the longest annual migration of any mammal on Earth. The Eastern Pacific population of whales starts the trip in waters off the coast of Alaska and travels approximately 75 miles per day. They can often be seen off the coast of California during their migration, where whale-watching is a popular activity.