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Gray Whale Migration on Monterey Bay

gray whale migration on monterey bay

December is the beginning of the gray whale migration season here in Monterey Bay, and we are hoping for another spectacular year! Winter whale watching season is another great time of year to come out on the Bay to witness one of the longest migrations of any mammal on earth.

Every year, gray whales start their 10,000 mile round trip migration by swimming south from the Bering and Chukchi seas to the warm water lagoons of Mexico’s Baja Peninsula, where pregnant mothers look for protection so they can give birth to their calves. Gray whales can also be seen courting and mating on their migration route and on occasion, early born calves can be seen swimming alongside their mothers.

These baleen whales are gentle giants and weigh up to 72,000 pounds, reaching lengths of up to 46 feet and live between 55 and 70 years. Newly born calves are about 15 feet long and can weigh close to 2,000 pounds (one ton)!

Gray Whale Calf

Gray Whale Calf

The gray whale is dark slate-gray in color and is identified by individual scars, patches, and their dorsal surface. The gray whale also lacks a dorsal fin, instead bearing 6 to 12 dorsal crenulations (“knuckles”), which are raised bumps on the midline of its rear quarter, leading to the flukes. This is known as the dorsal ridge. To spot gray whales out in Monterey Bay, look for a V-shaped blow as produced by their two blowholes on the top of their head that some say look like a heart.

After mating, gray whales without calves start their migration back North from February through March and return to their cold water feeding grounds. Last to leave the nursery lagoons of Mexico, typically in March to mid-April, are the mothers with calves who are finally ready to make their first journey.

Gray whales need a whopping 65 tons of food for their annual migration! The majority of their diet consists of small zooplanktonic, called amphipods, but they also consume other crustaceans like shrimp, mysids, and krill. Because of the abundance of these nutrients and the diverse food chain in Monterey from the submarine canyon, we are lucky to see a healthy number of the 20,000 gray whales that migrate through our backyard.

It is also interesting to note, that a population of about 200 gray whales are residents of the Pacific coast known as the Pacific Coast feeding group and can occasionally be spotted year round.