Gray whales 101: Facts on biology, migration, and more

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When Californians think of whales, they generally think of the species most sighted off our coasts — gray whales.

Swimming north and south, spouting, popping their heads out of the sea and endlessly curious about humans they encounter, gray whales are awe-inspiring creatures. They also are in trouble. More than 480 have been mysteriously found dead in the eastern Pacific since 2019.

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Basic gray whale facts

Length: Up to 49 feet
Weight: 90,000 pounds, more than a fully loaded semitruck
Color: The gray whale was named for the gray patches and white mottling on its dark skin.
Lifespan: Unknown, but estimated to be 40 to 80 years.
Speed: Generally 3-5 mph, but can swim double that speed when in danger.
Population: Roughly 19,000 (eastern Pacific gray whales)
Scientific name: Eschrichtius robustus

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Migration

Gray whales spend winters in the shallow lagoons of Baja California, Mexico, where females nurse their calves and others cavort and mate. They then travel north up the Pacific coast to waters off Alaska, their historical feeding grounds in the summer. Then, as winter approaches, they head south back to Baja.

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Biology

Mating: Gray whales reach sexual maturity at age 5 to 11 years.
Birthing: Mother gray whales nurse one calf at a time.
Pregnancy: Gestation period is 12 to 13 months.
Baby food: Whales are mammals, so newborn calves nurse on the milk of their mothers.
Blubber: Blubber is needed for energy, and also for insulation when the whales reach cold Arctic waters. Mothers and calves spend roughly two to three months in Baja before journeying north so baby whales can build up blubber.

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Whale and dolphin lingo

Test your knowledge of whale-watching terms:

Baleen: The bristle-like plates that hang from a whale’s upper jaw, used to filter prey, such as shrimp-like crustaceans, from the water. Baleen whales include all large whales, with the exception of orcas and sperm whales, which have teeth.
Blowhole: The nostril on the top of a whale or dolphin’s head. During dives, the blowhole is sealed by a nasal plug that opens when the animal surfaces. Baleen whales have two openings in their blowhole, while toothed whales have one.
Bow ride: When a whale or dolphin swims next to or in front of a vessel.
Breaching: When a whale or dolphin leaps out of the water, exposing the majority of its body.
Dorsal hump: Gray whales have a prominent dorsal hump followed by a series of knuckles along the dorsal ridge that extend to the flukes.
Flukes: The flat horizontal lobes that form the tail of all whale and dolphin species.

“Fluking” is when a whale flips its tail out of the water to help it dive deep at an angle. This whale is seen fluking at San Ignacio Lagoon, Baja California, part of El Vizcaíno Biosphere Reserve.

(Carolyn Cole / Los Angeles Times)
Fluking: When a whale or dolphin lifts its tail into the air to help it begin a sharply angled dive into deeper waters.
Foraging: Feeding or searching for food.
Krill: Tiny shrimp-like crustaceans eaten by whales, fish and birds, also known as euphausiids.
Lunge feeding: When whales, usually baleen whales, feed by lunging with open mouths through dense concentrations of fish or krill.
Mysticetes: All whale species that feed by filtering food through baleen plates rather than grabbing prey with their teeth.
Rostrum: The “snout” or “beak” of a dolphin or whale.
Spy hop: When a whale or dolphin raises its rostrum vertically above the water, then slips back below the surface. Possibly a means of obtaining a view above the surface.
Stranding: When a live or dead whale or dolphin comes ashore and is unable to get back into the water.

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Threats

A pod of orcas swims in Puget Sound west of Seattle.

(Associated Press)

Orcas: Also known as killer whales, orcas are often described as “gray whale enemy No. 1.” There are two main types of orcas — “resident” ones that feed primarily on fish and “transient” orcas that travel in packs, feeding on marine mammals. Gray whale calves are especially vulnerable.
Ship strikes: Scientists estimate that ships strike and kill scores of whales off the North American west coast each year. Over the last 15 years, global shipping traffic has tripled. Some projections forecast it could grow 1,200% more by 2050.

Food supply: In the Arctic, gray whales have historically fed on a species of amphipod — a type of crustacean — that has largely disappeared. As a result, gray whales have been forced to consume another species, and it is unknown if this new food source is as nutritious as their previous one.
Noise: Unnatural underwater sounds from boats, seismic air guns and other sources can disrupt communication among whales, and in extreme cases can cause hearing loss and depressed immune systems.
Fishing equipment: Discarded nets and traps can entangle and injure whales and make them more vulnerable to predators.

Marine debris, such as this entangled lobster trap in Maine, can harm whales and other marine mammals.

(Associated Press)

Other pollution: Whales migrating close to the west coast are exposed to surges of toxic runoff from stormwater, sewage plant failures and industrial discharges. As they feed, they also encounter litter tossed from boats and left on beaches.

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Some other whales of the eastern Pacific

Blue whales: Growing up to 98 feet long, blue whales are the largest of all whales, and the largest of all living creatures. Like other large whales, they were nearly hunted to extinction.

An 80-foot-long blue whale is seen between Santa Cruz and Santa Rosa islands off Southern California in 1999.

(Gary Phelps / Associated Press)

Fin whales: Slightly shorter than blue whales, fin whales are the second-largest leviathan.
Humpback whales: Named for their unusual body shape, humpback whales have long pectoral fins and knobs on their heads. Males produce a complex song that can last up to 20 minutes.
Sperm whales: Unlike gray, blue, humpback and fin whales, sperm whales have teeth and are known as the world’s largest toothed predator.