GRAY WHALE (Eschrichtius robustus)
[Eschrichtius-named after the Danish professor who worked with these animals, Daniel
Eschricht; robustus-strong]
Gray whales are medium sized baleen whales, reaching up to 45 feet (14 m) in length, with the
females usually being larger than the males. A mature gray whale can reach 40 t (44 short tons),
with a typical range of 15–33 t (17–36 short tons).They are gray with white patches, which
mostly consist of areas where barnacles and lice have attached themselves to the whales. In
fact, they carry over 400 pounds of barnacles and whale lice. The gray whale has no dorsal fin
but two-thirds of the way back on its body is a prominent dorsal hump followed by 6-12 knuckles
along the dorsal ridge that extend to the flukes (tail), pointed at the tips and deeply notched in
the center. Gray whale flippers are paddle-shaped and are also pointed at the tips. The tail itself
is 3–3.5 m (10–11 ft) across and deeply notched at the center while its edges taper to a point.
Individual whales are typically identified using photographs of their dorsal surface and matching
the scars and patches associated with parasites that have fallen off the whale or are still
attached.
All species of whale are broken down into two suborders. Baleen whales (which have
baleen plates and are the larger of the two suborders) have two blowholes while toothed
whales (which are smaller and have teeth) have a single blowhole. The blowhole(s) are located
at the top of the whales back (often on or near the head) and act as a passageway to the
trachea where air passes through and fills the lungs.
Blasting out of two blowholes, their exhaling breath creates two misty towers high in the air. If
it's not windy, the two towers of mist blend like a heart shape. The spout of the gray whale is a
noisy stream that rises 10-13 feet (3-4 m) above the water. It can be heard half a mile away.
Unlike humans however, whales do not breathe through their mouths because the trachea is not
connected to the whales throat. This separation allows whales to engulf their food while inhaling
or exhaling oxygen at the same time when near the surface of the water. More importantly by
having a separate air passage and food passage whales are able to swallow their food
underwater without worrying about taking water into their lungs.
The water that spouts from the blowhole is simply water that has collected around the
outside of the blowhole. The whales blowhole is surrounded by muscles to allow the
whale to dive without fear of taking in water. Researchers are unsure of whether or not whales
swallow large amounts of water when they engulf their food due to the high concentration of salt
in the salt water.
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Some species are known to expel the water by pushing it out with their tongue, while
keeping their food trapped inside the baleen plates, teeth or mouth, so it quite possible
that much of the water whales engulf comes from the water contents of the food they
swallow, since much of their food contains water within its body. Whales have specialized livers
and urinal systems to help them remove excess salt from the body when they swallow their food
and/or water.
Whales are also considered conscious breathers and never fall completely asleep because they
must come up for air or they will die. Although their brain is partially at rest half of their brain
remains alert in order to react quickly to life-threatening situations such as resurfacing for
oxygen or running from predators.
The California gray whale has been near extinction twice. The first time was after the discovery
of the calving lagoons in the 1850's. They made a brief recovery but the introduction of factory
ships in the early 1900's again pushed them to the brink of extinction. Protected from
commercial hunting since 1946, some hunting has been allowed for subsistence or for
"research." They were listed as "endangered" under the US Endangered Species Act of 1969
and further protected in American waters by the Marine Mammal Protection Act of 1972. The
Eastern Pacific gray whale was removed from the Endangered Species list in 1993 after
estimated numbers exceeded 21,000.
Gray whales are baleen whales, and each has approximately 300 plates of cream-colored
baleen hanging from its upper jaw. Two to five throat creases allow their throats to expand
during feeding. Sparse hairs are found on the snout, especially in young whales. The largest
plates are about 15 inches long and 10 inches wide. The baleen bristles are thicker than those
of the other baleen whales and are gray with yellowish bristles. The huge, narrow, pink tongue
of the gray whale is used to dislodge the food from the baleen, and weighs about 1-1.5 tons.
Gray whales congregated in small pods of about 3 whales, but the pod may have as
many as 16 members. Large groups (up to hundreds of whales) form in feeding waters,
but these are loose, temporary associations. They do not form long-term bonds.
Gray whales reach sexual maturity at 5-11 years of age, or when they reach 36-39 feet
(11-12 m) in length. The calf weighs 1,100-1,500 pounds (500-680 kg) and is about 15
feet (4.5 m) at birth. Calves nurse 7-8 months on milk that is 53% fat (human milk is 2%
fat). Females bear a single calf, at intervals of 2 or more years. Courtship and mating
behavior are complex, and frequently involve 3 or more whales of mixed sexes. Mating
and calving both occur primarily in the lagoons of Baja California, Mexico, including Laguna Ojo
de Liebre and Laguna San Ignacio, although both have been observed during the migration.
Gestation is estimated at 11-13 months, allowing the newly pregnant females to return
to the Arctic, feed during the summer, and then migrate back to the Baja lagoons in
plenty of time before their calf is born. Birthing usually occurs in the back reaches of the
lagoons (sometimes up to 30 miles from the entrance). Newly pregnant females often
join the birthing areas and help with the actual birthing and care of the young, much like
a midwife. Females who give birth will not mate until the following year. Thus, most
females give birth every other year after they reach sexual maturity.
The majority of gray whales feed in the cold arctic waters of the Bering, Chukchi, and
Beaufort Seas. Grays usually travel within 2.5 miles of the shore, staying in water that
is less than 300 feet deep, although at times they pass through deeper water. Their
migratory path has undoubtedly evolved as a response to changes in the earth's
climate. During the last ice age (18,000 years ago) they wouldn't have been able to
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access the rich amphipod beds of the arctic because of the Bering Land Bridge. As a
whale that lives along the coast, the gray whale has had to adapt to changing conditions
to survive.
During the Arctic winter, when the gray whale summer feeding grounds (Bering and
Chukchi Seas) are frozen, the whales migrate to protected equatorial lagoons to calve
and mate. Gray whale migration is the longest known of any mammal at 11,000 miles
(16,000-22,530 km) round trip, migrating each fall and spring, mainly along the western coast of
North America though not all whales make the migratory trip.
Migrating gray whales have predictable breathing patterns, generally blowing 3-5 times
in 15-30 second intervals before raising its fluke and then diving for 3-5 minutes. A gray
whale can dive up to 15 - 30 minutes. Mother gray whales are very protective of their calves,
and earned the name "Devilfish" from early whalers in lagoons because they often protected
their young violently.
Gray whales are the most coastal of the baleen whales and are often found within a
kilometer of the coast, although an increase in boat traffic seems to have forced the
whales to stay farther out. Because of their liking for inshore waters, gray whales are
some of the best known cetaceans. Gray whales are very agile swimmers and go 500 feet (155
m) deep, however, they can swim in even relatively shallow water without running aground.
Gray whales move through the water using up and down movements of their flukes.
They travel both night and day at speeds of 3-6 miles per hour, averaging 80-100 miles
a day. It takes about 2 months to complete the one-way migration. On the trip north they travel a
little slower, especially the mothers and calves that stop to nurse and rest.
They also breach, jumping partially out of the water and falling back at an angle,
splashing and making a loud noise. This may help clean off some of the encrustations of
parasites (barnacles and whale lice) or in communicating with other gray whales.
Spyhopping is another gray whale activity in which the whale pokes its head up to 10
feet (3 m) out of the water, turning around slowly, to take a look around.
Gray whales (like all baleen whales) are seasonal feeders and carnivores. They are
bottom feeders (benthic feeders) that filter out small crustaceans (1/2 inch (1.2 cm)
long shrimp-like crustaceans called amphipods, krill, copepods, etc.), plankton, and
mollusks (including squid and fish) from the ocean sediment. Amphipods are very
abundant in the northern waters during the summer because the longer days produce
more phytoplankton and zooplankton, the food amphipods feed upon. Gray whales are
the only bottom feeding whale. A single gray whale is believed to turn over 50 acres of
sediment during a season of feeding. The mud thus churned is oxygenated, exposed to
the nutrient rich water and is in effect seeded for the next years harvest. These
crustaceans are found in relatively shallow waters between about 25 feet and about 150
feet deep.
During feeding, the gray whale appears to prefer using its right side to scour the bottom
and find its food. To feed they gulp mouthfuls of mud from the bottom, then use the
whiskery baleen as a filter to drain out the unwanted material. This leaves the
amphipods stuck to the baleen inside their mouths. They then use their tongues to
loosen the amphipods from the baleen, and swallow.
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During migration and while in calving areas, gray whales eat very little, although they
occasionally will eat shrimp-like mysids or small fish at the surface. Thus the blubber
they add during the summer feedings must provide energy for the remainder of the year.
Gray whales spend about 6-7 months of their year feeding in Alaskan waters above the
Arctic Circle and only about 1 month (for males and females without a calf) in Mexican
waters. Cows with calves spend about three months in the lagoons. It takes gray whales
about 4 months to migrate to and from the lagoons (2 months each way).
PREDATORS AND PARASITES
Killer whales (orcas), the large sharks, and humans are the gray whales' only natural predators.
Orcas hunt gray whales off the Pacific Northwest coast near Oregon, USA. Skin parasites
(including barnacles and whale lice) attach themselves to the head area, back, and blowhole
area also. Orca (killer whales) are the gray whale's main predator and many gray whales have
orca teeth scars on their flukes. The young calves on their journey north are somewhat easy
prey for orcas. Gray whale life expectancy is anywhere from 40 - 70 years.
VOCALIZATION
Gray whales emit grunts, clicks, and whistling sounds. These sounds and those
produced by breaching are used in communication with other gray whales. Scientists have long
known that man-made, underwater noises — from engines, sonars, weapons testing, and such
industrial tools as air guns used in oil and gas exploration — are deafening whales and other
sea mammals.
Scientists have discovered that whales can decrease the sensitivity of their hearing to protect
their ears from loud noise. Humans tend to do this with index fingers; scientists haven’t
pinpointed how whales do it, but they have seen the first evidence of the behavior. The noise
threat arises because of the basic properties of seawater. Typically, light can travel for hundreds
of feet through ocean water before diminishing to nothingness. But sound can travel for
hundreds of miles.
The world’s oceans have been getting noisier as companies and governments expand their
undersea activities. Researchers have linked the growing racket to deftness tissue damage,
mass strandings and disorientation in creatures that rely on hearing to navigate, find food and
care for their young.
The heads of whales and dolphins are mazes of resonant chambers and acoustic lenses that
give the animals not only extraordinary hearing but complex voices. The distinctive songs of
humpback whales appear to be sung exclusively by males seeking mates. In recent decades,
scientists have linked the human cacophony to reductions in mammalian vocalization, which
suggests declines in foraging and breeding.
It is thought that mother whales on their way back to the Bering Sea with their calves tend to
hug the coastline where the wave action and shallower waters disrupt the sonar signals
broadcast by Orcas that identify their prey.
Frank Schiavone added the following:
Once numbering in the tens of thousands in the Northern Hemisphere, the Atlantic gray whale
became extinct in the 1700’s. Today, gray whales are only found in the North Pacific. There are two
distinct genetically different populations – the Western North Pacific (WNP) and the Eastern North
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Pacific (ENP). The WNP population is nearly extinct with fewer than 130 individuals according to the
most recent survey data compiled in 2008. WNP gray whales are listed as critically endangered by the
ICUN. The Eastern Northern Pacific gray whale population, on the other hand, is robust and its
recovery has been nothing short of remarkable. The most recent (NOAA Fisheries) estimate of
abundance is based on southbound survey data from 2006/2007. It puts the number of ENP gray
whales at 19,126. Estimates from 2007/2008, 2009/2010, and 2010/2011 have not yet been compiled
or are available.
WNP gray whales were delisted in 1994 when the population level was thought to have reached prewhaling levels (roughly 18,000 individuals). An unusual mortality event or UME occurred in 1999 and
in 2000 reducing numbers by one third. Over 60% of dead whales were adults. Strange since, as a
rule, calf strandings are far more common. The UME is still being debated but it is thought that limited
food availability was the underlying cause. Fortunately, current trends and oceanographic conditions
suggests that the high mortality was not a chronic problem as the population has recovered fully to
the levels prior to the UME. Based upon genetic studies (looking at mitochondrial and nuclear variation) by S. E. Alter, Steve
Palumbi, and others it is likely that Pacific gray whales once numbered 96,000 animals some 1100 to
1600 years ago. Today, estimates are that the current gray whale populations are at roughly 85% of
carrying capacity and “within the range of its optimum sustainable population (OSP)”.
So how will climate change impact the ENP gray whales?? Reductions in Arctic sea ice will
undoubtedly affect their summer range. Their salvation will be their “trophic plasticity” as Gray whales
are both benthic and pelagic feeders. As Artic ice melts pelagic prey will likely increase while benthic
prey will likely decrease. Gray whales will be far better suited than trophic specialists that have very
specific diets. Gray whales, however, may be negatively impacted by ocean acidification as it will
reduce shell-forming animals which are important food sources to them.
See NOAA Fisheries Stock Assessments for more information.
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