Beast
Feast
By Susan Payne, NOAA
Feeding is the main activity of hungry whales returning north. They lived off nothing but their fat reserves for months along the migration trail and in the warm lagoons of Mexico. Whales must gain back all the weight they lost. An adult gray whale eats approximately 2,400 pounds of food a day, scraping its nutrition off the bottom of the ocean. It swallows at least 67-77 tons of food during a 5- or 6-month feast on the Arctic feeding grounds! Biologist Susan Payne in Kodiak, Alaska, tells scientific information about the feasting of gray whales:
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Baleen
in the Mouth Photo Mike Hawe |
Gray whales migrate to their northern feeding area to feed on the dense, rich, tiny benthic (bottom-dwelling) creatures of the Bering and Chukchi seas. The gray whale's short baleen has been adapted for collecting this bottom-dwelling food. Scientists have noted that the whale's right side is often different from its left side. The baleen on the right side shows more wear. The head has fewer barnacles and skin abrasions. To scientists, these are signs that the whales turn onto that side to feed on the ocean floor. Then, with their mouth 10-20 cm above the surface of the ocean bottom, they create a pulsating suction by depressing their tongue. The suction pulls the prey from mud as deep as 20-30 cm. The grooves made by a whale's mouth plowing along the muddy ocean floor are called feeding tracks. Feeding tracks are slightly curved. They measure 1 to 3 meters long and from 0.5 to 1.0 m wide (Nerini, 1984).
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Favorite Feeding Grounds
As bottom feeders, gray whales like to feed in shallower waters. Their
favorite feeding grounds in the northern Bering Sea is a shallow
region less
than
50 meters
deep.
They also
prefer an
area less than 68 meters deep in the southern Chukchi Sea. The Chirikov
Basin, located north of St. Lawrence Island (63.50N, 170.17W)
and south of the Bering Straits (66.00N, 168.50W), is dominated by a
community of amphipods, Ampelisca macrocephala. (Get a good
map and use the latitude and longitude to locate these places.)
Gray whales also feed in the Western Bering Sea, the southern capes of St. Lawrence Island, the southern Chukchi Sea, and the north side of the Chukchi Peninsula. The prey in these areas includes not only amphipods but also cumaceans and isopods (Nerini, 1984). (These are all scientific names for very small creatures. Do research to find pictures of them.)
Acrobatics Aid Feeding
 Photo Keith Jones |
Besides benthic feeding in some areas, gray whales along their migratory route have also been reported to feed on pelagic species. These include schooling squid, krill, small bait fish such as capelin, crab larvae, herring eggs, and ghost shrimp.
Here in Alaska where I live, whale watchers off Kodiak's Narrow Cape like to watch whale acrobatics. We see whales in the surf standing on their heads with their flukes in the air, or lying on their sides with flippers out of the water! According to James Darling of the West Coast Whale Research Foundation, these whales may be feeding on mysids, little critters hiding under rocks. Gray whales also feed on species such as crab larvae, found in plankton. When feeding on plankton, whales can be seen skim-feeding with their upper jaws above the surface of the ocean. It looks like they are biting at their prey.
National Science Education Standards
- Organisms have basic needs.
- Each plant or animal has different structures that serve different functions in growth, survival, reproduction.
- All organisms must be able to obtain and use resources, grow, reproduce, and maintain stable internal conditions in a constantly changing external environment.
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