Pacific Gray Whale Facts | Baja Wildlife Guide

PHYSICAL CHARACTERISTICS

All whales are warm-blooded creatures that have common traits shared by most mammals: they breathe oxygen, have a layer of blubber, give birth, produce milk and have hair (small hairs can be found at the top of the rostrum on a calf). These baleen whales reach upward of 45 feet long, although the adult female may be slightly larger, and both sexes typically weigh between 30 and 40 tons. Members of this species can expect a lifespan of about 30 to 50 years, although some may live until the age of 60.

This species gets its name from its blotchy-colored skin pattern, which is mottled gray speckled with white, pale yellow or burnt orange barnacles and parasites, known as whale lice. These patches are found at the tip of the head, surrounding the blowhole, and toward the anterior region of the back. The gray whale has a streamlined body, with a narrow, tapered head, which gives it a conical shape. Its arched upper jaw, called the rostrum, overlaps the lower jaw by a margin. The rostrum is dimpled, each bump containing a single stiff hair. Between two and five grooves, measuring 5 feet in length, are located on the ventral throat that allow for limited expansion of the whale’s throat during feeding. Gray whales possess neither a dorsal nor a back fin. Instead, they have a protruding dorsal hump, which is located two-thirds back along the body and is followed by 6 to 12 knuckles that proceed down the dorsal ridge until reaching the tail. The whale shark’s paddle-shaped flippers have pointed tips, and its V-shaped tail flukes measure 10 to 12 feet across.

SENSES

Hearing is the most crucial sense a gray whale possesses. Sound travels further and four times faster in water than in air. It is believed that these whales can hear very low frequencies, and their superior hearing is of better use in dark ocean habitats because of their poorer vision.

Sight
There is some uncertainty about how well whales can actually see because their eyes are relatively very small—about the size of a baseball. The gray whale’s eyes are positioned toward the back of their head, which gives them two fields of vision on either side of the body. This monocular vision limits their depth perception and may make it more difficult to see their surroundings. Sight is crucial only when close to breaching the ocean’s surface, as they rely on their other senses to navigate the murky depths where little light shines through.

Smell
A whale’s sense of smell is highly compromised and may be nonexistent. The brain’s olfactory bulb is essential to olfaction, but it is greatly reduced in baleen whales.

Touch
Gray whales possess vibrissae, which are whiskers on their snouts that help detect their surroundings tactilely, much like cats. Cetacean skin is also highly sensitive to touch.

Magnetism
It is thought that gray whales may gain directional cues during long migrations by relying on the earth’s magnetic field. This sense of magnetism is not fully understood, though mass beaching of whales is often found at sites where an anomaly occurs in the magnetic field, perhaps leading the whales astray.

FEEDING HABITS

These baleen whales have upper jaws that house a series of overlapping, fringed plates—130 to 180 in number. The cream-colored plates are made of keratin that split into fine hairs on the ends near the tongue. The plates—2 to 10 inches long and placed one-third of an inch apart—form an overlapping screen that aids in trapping prey while expelling water.

Unlike most baleen whales, the gray whale is primarily a bottom feeder and must get food from the sediment on the ocean floor; they feed mainly on small crustaceans such as amphipods (tiny shrimplike animals) and tube worms that are found in this sediment. The gray whale feeds mainly in the Chukchi and Bering seas of Alaska during the summer.

To feed, a whale will dive to the ocean floor, even up to 395 feet deep, although it prefers to feed in much shallower water. Once it reaches the bottom, the whale will roll on its side and draw the sediments and waters into its mouth, which is 1 foot deep and has a surface area about the size of a desk. As it shuts its mouth, food is trapped in the baleen fringes as water and sediment are filtered out of the plates. The baleen plates have stiffer, coarser bristles than other baleen whales because they must filter out sediment in addition to water. Gray whales will stay under water for three to five minutes to eat, leaving behind a trail of dents in the ocean floor.

The feeding season for gray whales lasts from mid-spring to mid-fall. The majority of the population travels to the frigid Arctic waters of the Chukchi and Bering seas, though some gray whales feed farther south from British Columbia to Mexico. Along the Oregon coast, between 200 and 400 whales can be found during summer months. The whale’s summer food supply of marine life, primarily bottom-dwelling amphipods, is usually more plentiful at higher latitudes; the longer days produce a large amount of phytoplankton, which are consumed by zooplankton, a staple of many sea creatures’ diets.

VOCALS

Scientists have recorded a large repertoire of gray whale calls while at their mating and birthing grounds. These whales display comparatively lower levels of vocal activity at their feeding grounds. Research suggests that vocals are an important means of attracting a mate or are used so by females to communicate with their calves. However, in the northern feeding grounds where predators such as killer whales lurk, vocal activity is restrained to avoid potential detection.

Some vocalizations can be heard above water; sailors of old believed the whistles and moans of a whale were the callings of mermaids or sea monsters. The sounds produced by a gray whale include a series of clicks, rasps, roars, squeaks, and grunts and groans and are made either by pushing bursts of air through the lungs or the blowhole.

BREATHING

All whales must surface in order to breathe. When gray whales breach, they blow a jet of vapor into the air, which can reach a height of 15 feet. The spout produced from the blowhole takes the shape of a heart when viewed from the back or head-on. The whale blows three to five times in intervals of 15 to 30 seconds, lifting its tail before submerging back into the ocean, and then rising again in three to five minutes.

Gray whales remain underwater no more than 15 minutes. Marine mammals rarely drown, unless they become entangled in fisher’s nets and are unable to surface. Suffocation can occur in calves born underwater, who must feel the touch of air on their skin in order to take their first breath; some newborns never reach the surface.

SHORE HABITS

Shallow water can be dangerous for larger whales because they often become stranded. Gray and right whales, however, manage to swim in very shallow water. In lagoons, they negotiate the seemingly treacherous turbid channels, withstanding the strength of the tidal currents. Feeding grounds may often be in shallower regions—in furrows on the outer edge of breaking waves along sandy beaches. Sometimes humans, spotting how close the whales are to shore, call in reports of stranding when in actuality, the whales are merely feeding at low tide.

REACTION TO HUMANS

Subsequent studies on the impacts of salt production in the lagoons indicate that gray whales are adaptable creatures, changing their behaviors in light of human disturbances. They have been observed circumnavigating barge traffic and evading or being indifferent toward fishing and touring vessels. Sometimes, curious whales will approach a ship, even allowing passengers to touch them. It appears that these whales adapt well to new sights and sounds unless they feel threatened with physical harm. In a study done in Baja, California, the sounds of orcas and oil drilling were projected into the waters of Laguna San Ignacio: these alone caused the gray whales to flee.

The gray whale is a resilient, adaptable species, apparent by its recovery and removal from the Endangered Species List in 1994. Comprehensive, long-term studies are required to better understand the impacts of human activities on gray whale behavior, reproduction, lifespan and habitat. From this information, we can gather how to best manage the gray whale’s winter grounds in Mexico and the areas throughout their migratory range.

PREDATORS

A gray whale’s only natural predators are large sharks and killer whales. Orcas in the Pacific Ocean hunt gray whales along the coast of Oregon in late April and May, often targeting females and calves that are migrating north. In fact, evidence of these encounters may be seen directly on the whales’ bodies; many gray whales have visible orca teeth scars on their flippers and flukes. The biggest threat to gray whales are humans, especially when whales become entrapped in fishing nets, grow sick from polluted water, and lose crucial food sources from overfishing.

MATING

Both female and male gray whales reach sexual maturity at 5 years old, or after they reach 35 feet in length. Mating generally takes place near and in the lower ends of the lagoons. Females first ovulate in November, so most mating occurs in the north, but if the female has not mated, or if the mating is infertile, she will ovulate a second time in 40 days. Matings that are observed farther south in January probably are of this category. The gestation period is calculated to be 13 months, so births occur mainly in January when the expectant female has reached the lagoon.

At the beginning of courtship, the female swims evasively, with one to seven males in pursuit. The courting whales roll over in the water, extending their flippers alternately like spars. Gradually, the males drop out, until normally only two remain. By now, the female has slowed and the males crowd her flanks. The female surfaces, usually upside down and spiraling; the males then swim up onto her body, grazing her genital area. Next, the female stops moving and may be rolled over when the males try to mount. The males flank the female on either side, clasping her body with their flippers to stop the rolling, using their weight to force her tail area down. This causes her to pivot her head up out of the water and then to sink tail first. The heads of the males also break the water whenever they slide up onto her body.

Considering the size of these whales, the gentleness of their contact is amazing. Except for rolling, the movements are reminiscent of a slow-motion film. The males may follow the female, as she dives vertically downward, exposing their tails. When the female is thoroughly aroused, she lies at the surface, upside down with her flippers extended. The males swim upside down alongside with their genital organs exposed. These organs are curved and sufficiently long enough to reach across the not inconsiderable girth of the female to touch her midsection.

The two males will adjust their position to contact the female’s genital opening. There is also some positioning of the genital organ by extension and rotation. As soon as the genital organs are in contact, the pair rolls toward each other to complete the coupling. The separation of the pair does not necessarily connote the end of courtship, as the threesome may stay together throughout the rest of the day. The bond between female and males, however, is a short affair; females have been observed mating with three different males within a 45-minute span.

Header Credit: Bill Gent & Diana Russler

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