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How Gray Whale Calves Learn to Feed

Gray whales are on the return leg of their annual migration, heading from Baja California’s breeding lagoons to the Bering and Chukchi seas in the Arctic. Map source: Wikipedia, Creative Commons

A whimsical welcome letter to gray whale calves from the imagined “Bering & Chukchi Seas Dining Services.”

May 2013

Dear Gray Whale Calf,

Congratulations on completing your first northbound migration!

Welcome to the Arctic Ocean. This is where many gray whales feed during the summer (and soon, so will you). Swimming 85 to 100 miles a day on the northbound migration burns a lot of calories—it’s time for a hearty Arctic meal. Before you know it, you whales will migrate again, so it’s important to pack on the pounds.

Here, in the nutrient-rich waters between Russia and Alaska, there is a seafood smorgasbord! Patches of the muddy seafloor are full of baleen whale delicacies: shrimp-like animals called amphipods, worms, fish eggs, and molluscs. The body fat you gain from these foods will nourish you during the next migration (when you rarely feed).

This is also an exciting time, because shortly, you will no longer need to drink your mother’s milk.[1] This summer, you will begin mimicking how she feeds while accompanying her on dives to the amphipod beds.[2]

Learning to strain prey from the seafloor can be challenging for some calves at first. Most aren’t used to the feeling of mud between their baleen plates. Others worry about their mouths constantly being exposed to frigid Arctic water. But gray whales have special blood vessels at the base of their tongues to reduce the amount of heat that dissipates when you feed. In fact, scientists were surprised to learn that a calf loses more heat through its blubber than its tongue!

Gray whale head and mouth.

Gray whale head and mouth.

If you can’t find enough food, move to another area. Follow the lead of other gray whales, which have been traveling farther north in the past two decades.[3] You can also switch behaviors and feed on another type of prey. Biologists think gray whales are an intriguing marine mammal because you have flexible feeding strategies.[4] Not only can you suction feed, but you can suck or skim swarming shrimp and crab larvae from the water and engulf small fish. Gray whales that spend their summers near British Columbia and Washington use this feeding technique.[5]

Mom will stay by your side for the next few months, but by winter, you will be a fully independent gray whale and responsible for finding all of your own food.

Best of luck and happy grazing!

–Bering & Chukchi Seas Dining Services
(written by Kate Jirik, aquarium naturalist)

 

Birch Aquarium’s 2013 whale watching season ended April 14. Thousands of passengers experienced this amazing migration with our naturalists and the aquarium’s partner, Flagship Cruises & Events. We hope to see you for next year’s migration, beginning in December!

 


[1] Calves are weaned 7-9 months after they are born, typically mid-August through October (swfsc.noaa.gov).

[2] Dave Weller, PhD (gray whale biologist). Personal communication, 10 December 2013.

[3] Ibid.

[4] Interestingly, the use of diverse feeding modes may have helped gray whales survive the last ice age (Pyenson and Lindberg 2011, PLoS ONE 6(7):e21295).

[5] Stelle, LL, WM Megill, and MR Kinsel. 2008. Activity budget and diving behavior of gray whales (Eschrichtius robustus) in feeding grounds off coastal British Columbia. Marine Mammal Science 24(3):462-478.

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