Gray Whales: Mud, Mating and Migrating

A gray whale. Photo courtesy of NOS/NOAA/MBNMS.
Two gray whales. Photo courtesy of NOS/NOAA/MBNMS.

Have you seen any heart-shaped puffs of mist from the ocean offshore California lately? If so you were likely close to a gray whale. Gray whales arguably hold the record of having the longest mammal migration on earth and they are passing by Central Coast waters now. Starting in winter, gray whales (Eschrichtius robustus), are off on their 11,000-mile trip south and then head back north to the Arctic by summer.

The Great Migration: When to See it

Grays begin their migration in November heading south to the bays and lagoons of Baja California. Most of the whales passing the Central Coast during November and December are pregnant females racing to warmer waters to give birth. In mid-January, the rest of the gray whale population passes by.

They return north from mid-February to early summer; this is peak migration time and the Monterey Bay is a great food source. Northwest winds push the surface water offshore, replacing it with nutrient rich cold water from greater depths. This “upwelling” fuels the growth of plankton which are the basis for the Monterey Bay National Marine Sanctuary’s rich marine food chain. The richest waters are centered along the submarine canyons that come close to shore. Look for them just beyond the kelp forests. The gray whales come close enough that you can see the growth of whitish barnacles and pink “whale lice” on their skin – even without binoculars.

The gray whale migration route. Photo courtesy of NOS/NOAA Fisheries.
The gray whale migration route. Photo courtesy of NOS/NOAA Fisheries.

Mud Munching

Grays feed in a very unusual way. They dive to the bottom, lay on their sides and scoop up great gobs of mud which they filter through their baleen. The bristles of the baleen trap inch-long, fat-rich amphipods that get whisked down their throats using their huge tongue. Grays spend the summer in the Bering Sea or the Chukchi Sea, between Russia and Alaska feeding on the food rich muds.

Big as a School Bus

A full grown gray whale can be 45 feet long and weigh 40 tons but, even so, are often surprisingly hard to see. They are a mottled gray, with white patches of barnacles over their bulky body and a narrow, V-shaped head. The shape of the spouts gives you the first clue grays are around. The water tends to make a heart-shape: different from the more straight-up spout of blues and humpbacks.

A heart-shaped gray whale spout. Photo by  Linda Tanner via Flickr Creative Commons.
A heart-shaped gray whale spout. Photo by Linda Tanner .

Typically grays only come to the surface for a short time. They give a quick couple of spouts, a roll of the back, and then they’re down for 5 or 6 minutes or more. Just long enough for you to get bored and look away.

Increasing Numbers

In the 1970s, whale sightings were few because their populations had been depleted due to world whaling practices. Thanks to anti-whaling laws that began in the 1940s, but were really given teeth in the US and internationally in the 1970s, many species have made a strong recovery. Gray whales have been taken off the endangered species list, while the numbers of humpback and blue whales have increased.

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About The Author

I really enjoy field trips. I love being in a cool place and having someone tell me about it. The problem is, you can’t always find a professor or park ranger-type to tell you all they know about the local rocks, plants, and history. So I decided to combine my love of things natural with mobile technology.

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