The gray whales are on the move!

0
132
 

The following article is one in a series of articles written by Heal the Bay, which will focus on different marine animals found in the Santa Monica Bay. This is the last month of whale watching, and the following story gives interesting facts and information on the migration of the gray whale population.

Gray whales, Eschrichtius robustus, spend their lives in the eastern Pacific Ocean and closely follow the North American coastline during their annual migration from the Arctic seas to the Baja California peninsula. These “coastal” whales make one of the longest of all mammalian migrations, averaging 10,000 to 14,000 miles round-trip. Usually around October, whales begin to leave the rich feeding grounds in the Bering and Chuckchi seas and head south for the warm lagoons of Baja, Mexico where some whales mate and those that are already pregnant give birth. This southward migration takes about two to three months to complete. The whales stay at the lagoons for another two to three months, using this time mainly for feeding. Gray whale calves, which are 15-feet long when born, drink as much as 50 gallons of milk per day. This milk, which is 53 percent milk fat (human milk is 2 percent milk fat), allows the calves to build up a thick layer of blubber to sustain them during the two- to three-month northward migration and to keep them warm in the colder waters. Mothers and calves travel very near shore on the northbound migration and can easily be seen from Point Dume and several places in Palos Verdes.

How do I know it’s a gray whale?

Gray whales get their name from their gray color, which is mottled in adults, with patches of whitish barnacles and orange whale lice. An adult gray whale can grow to be 45 feet long and can weigh between 30 and 40 tons. These whales lack a dorsal fin, and instead have a series of six to twelve dorsal knuckles, or ridges, that begin about two-thirds of the way down the body and extend to the tail. A gray whale has a predictable breathing pattern, especially during the migration. It will “blow” (exhale then inhale) approximately three to five times in 15- to 30-second intervals, staying close to the ocean surface the entire time. Then the whale will raise its fluke, or tail, and dive down where it can stay submerged for three to five minutes. During migration a gray whale can travel at three to six miles per hour.

How are the whales doing?

Not long ago, there were three distinct, separate gray whale populations: a North Atlantic population, which is now extinct from over-hunting; a western North Pacific population which was thought to be extinct (we now realize there are a few hundred animals left); and the eastern North Pacific population, which is the largest surviving gray whale population. The eastern North Pacific population is estimated at 23,000 to 25,000 animals, which is considered to be at or near pre-whaling levels. This population neared extinction in the 1850s after the discovery of calving lagoons, which were easy hunting grounds. In fact, the whales were what is now called “commercially extinct,” meaning that their numbers were so few they were not worth the expense of hunting. Their population partially rebounded in the early 1900s, but with the advent of steam-powered ships they were hunted to near-extinction again. Finally, the International Whaling Commission granted the gray whale full protection in 1947, which has once again given the whales a chance to survive.

To learn more about the gray whale migration, visit acsonline.org