Gray Whale Migration
Summer: July, August, September

Gray Whale Migration Route
(Click on face of map)

On the Arctic Feeding Grounds
The whales haven't eaten much for months, mostly fasting until their arctic feeding grounds are once again ice-free. When the gray whales finally reach their summer feeding grounds in the Bering and Chukchi Seas, it's time to feast!

By June and July, the whales are said to be as thick as a huge grazing herd. For months they've been living off fat reserves in the calving and mating lagoons, and along the migration trail. Even though they appear to do a small amount of feeding in fall and winter whenever they can find a food source, whales have a LOT of weight to gain back. Each whale must grow strong and fat before migrating in autumn to the breeding and calving grounds over 5,000 miles south. During its five- or six-month feast on the arctic feeding grounds, an adult gray whale will swallow about 70 metric tons of food.

Do you see the 3-5 throat grooves on the underside? These expand when the whale is feeding.
Photo Mike & Winston.

A jar of krill—a favorite whale food. Shauna Bingham, Channel Islands Marine Sanctuary

Summer feeding is better at higher latitudes. Why? Daylight is almost 24 hours, and such long days produce lots of phytoplankton. These tiny marine plants are eaten by zooplankton (tiny marine animals). Together, these are the basic food for all ocean life. A lot of plankton stimulates the growth of the marine food web, including bottom-dwelling amphipods. Amphipods are the primary prey of gray whales. It takes a lot of those tiny critters—an estimated 300 kg (660 lb.)—to fill a gray whale's stomach!

As bottom feeders, gray whales help other species. Over a feeding season, one gray whale willl sift through a hundred acres or more of seafloor. One square foot of Bering Sea sediment might yield less than half an ounce of amphipods in certain sections, so the whales also spend lots of time searching for food. All this foraging stirs up nutrients that come to the surface for birds to eat.

Eventually the days shorten. The air chills, and water starts turning into ice. The whales know it is time to swim south again in a yearly cycle continues for as long as they live.

Summer Lessons

  • Beast Feast
    How much food will a gray whale eat during the summer? Where are their favorite feeding grounds?