How Far Do Gray Whales Migrate? Mexico to the Arctic

How far is the gray whale migration?

The eastern North Pacific gray whale travels about 8,000–11,000 km (5,000–6,800 mi) each way, depending on where it feeds and where it spends the winter. NOAA describes the round trip as about 10,000 miles (16,000 km), and in some cases more than 14,000 miles (22,500 km).

That is a remarkable distance for a whale that weighs up to about 40 tonnes and eats little on the way. Whales on migration swim day and night at an average of about 8 km/h (5 mph), covering roughly 120 km (75 mi) a day. Over a lifetime of several decades, an adult may swim the equivalent of many trips around the world.

Gray whales share the title of longest mammal migration with the humpback whale, some of which travel 8,000 km (5,000 mi) or more in one direction between polar seas and the tropics. No mammal comes close to the Arctic tern, though, which flies around 70,000 km (44,000 mi) a year; see Which bird has the longest migration?

The route from the Arctic to Baja California

In summer, most eastern gray whales feed in the shallow Bering, Chukchi and Beaufort seas, sucking up small crustaceans from the seafloor. As the days shorten and sea ice starts to form in autumn, they head south through the Aleutian Islands, mostly through Unimak Pass, and follow the coastline of Alaska, British Columbia, Washington, Oregon and California.

Their destination is a string of warm, shallow lagoons and bays on the Pacific coast of Baja California Sur. The three most important are Laguna Ojo de Liebre (once called Scammon’s Lagoon), San Ignacio Lagoon and the Magdalena Bay complex. Pregnant females give birth there or along the way, and other whales court and mate.

Not every whale makes the full trip. About 200 whales, the Pacific Coast Feeding Group, stop for the summer between northern California and British Columbia. A small group also returns each spring to Puget Sound in Washington, near Whidbey Island, to feed on ghost shrimp before continuing north.

When do gray whales pass the US West Coast?

The migration runs on a reliable calendar, although the timing shifts a little from year to year.

The southbound migration is the more concentrated of the two, peaking off central California around mid-January. Pregnant females lead, followed by other adults and then young whales. In the lagoons, the number of whales peaks between mid-February and mid-March.

The northbound migration comes in two waves. Males and females without calves leave the lagoons first, from February. Mothers with newborn calves stay longest, until the calves are strong enough, and travel north from about March to May. They often swim very close to shore, which may help them avoid orcas that wait along the route.

Why do gray whales migrate so far?

Gray whales migrate because the best places to eat and the best places to give birth are thousands of kilometers apart. The Arctic seas are rich in food in summer, when long days fuel huge numbers of seafloor amphipods, but they freeze over in winter and are cold for newborn calves.

The Mexican lagoons have almost no food for gray whales, but they are warm, calm and shallow. Scientists think this protects calves, which are born with little blubber, from cold water, rough seas and predators such as orcas. Mothers nurse their calves on very rich milk, and by spring the calves have enough blubber for the long swim north.

To make the journey, adults rely on the energy they stored as blubber during the Arctic summer. They largely fast for months on end, losing a large part of their body weight before they can feed heavily again in the north.

Record journeys of western gray whales

The most remarkable migrations come from the small, endangered western gray whale population, which feeds off Sakhalin Island in the Russian Far East. Scientists had assumed these whales wintered off Asia, but satellite tags told another story.

In 2011, a female nicknamed Varvara was tagged off Sakhalin. She crossed the Bering Sea and the Gulf of Alaska, swam down the coast of North America to the breeding lagoons of Baja California and then returned to Sakhalin, about 22,500 km (14,000 mi) in 172 days. The study, published in 2015, described it as the longest recorded migration of any mammal. Photo-identification and genetic matches have since shown that some western whales regularly mix with the eastern population in Mexico. The journey also appears among the longest animal migrations on Earth.

How do gray whales find their way?

No one knows exactly. Gray whales migrate close to the coast, and they may simply follow the shoreline, perhaps using the shape of the coast, the sound of surf and the depth of the seafloor as guides. Many scientists also suspect that whales can sense Earth’s magnetic field, as some birds and sea turtles do, but this has not been proven.

Young whales probably learn the route on their first journey with their mothers. Whatever the method, gray whales are remarkably consistent, returning to the same lagoons and feeding areas year after year.

Where to watch the gray whale migration

The migration is one of the easiest whale shows in the world to see from land. Good places include Cabrillo National Monument in San Diego, Point Vicente on the Palos Verdes Peninsula, Point Reyes and Monterey Bay in California, and Depoe Bay and Yachats in Oregon. Oregon holds volunteer-staffed whale watch weeks around the winter holidays and the spring break.

In Mexico, licensed small-boat trips in the Baja lagoons offer close views of mothers and calves from about January to April. Wherever you watch, keep a respectful distance: NOAA advises vessels to stay at least 100 yards (91 m) from whales.