by Lisa Taylor, student in Geography 316, Fall 1999
San Francisco State University
Geography 316: Biogeography
The Biogeography of The Gray Whale (Eschrichtius robustus)
by Lisa Taylor, student in Geography 316, Fall 1999
Kingdom: Animalia
Phylum: Chordata SUBPHYLUM: Vertebrata
Class: Mammalia SUBCLASS: Cetacea
Order: Mysticeti
Family: Eschrichtidae
Genus: Eschrichtius
Species: Eschrichtius robustus
Introduction
The Gray Whale, Eschrichtius robustus, one of the most observed of all whales,
are best known for their 1,200-mile round trip between its southern grounds in Baja
California, Mexico and its northern feeding grounds in the Bering and Chuckchi
Sea. Gray Whales have history along the Pacific Coast, and at one time was hunted to
the brink of extinction by a culmination of Siberian and Alaskan natives and commercial
Whaling. Once protected the populations flourished. But the current
dilemma of Grey whales is a massive salt factory located in last pristine habitat for the
Gray whale.
Description of Species
The Gray whales have an unmistakable profile. They
have a sharply pointed bowed head, no dorsal fins, and a series of knuckles or bumps
(usually-10) along the mid-line of the lower back (Watson 1981). The tail flukes are
not especially large but are always abraded so that the tips are worn and rounded with the
trailing edge visibly serrated (Watson 1981). Gray whales are unusually hairy with
irregular rows of bristles on the top of their head and along the side of the lower jaw,
with the largest amount in tuffs on the tip of the snout. The eyes are small circles
surrounded by skin folds. Another unique feature is along the throat were there are two
(sometimes four) longitudinal grooves about two meters in length. Gray whales like their
name implies, are dark gray in color and most individuals are blotched with lighter flecks
due to barnacles. (Watson 1981)
Gray whales are one of the largest whale species,
averaging forty feet in length. Males can reach a maximum length of fifty feet and weight
to up to 34 tons. Females can reach a maximum length of 42 feet and weight up to 38
tons in weight.
Calves at birth are fifteen feet long and weigh between 1,500 to 3,000 pounds at birth (Watson 1981). Gray whales are baleen in their feeding mechanism. They have an average of 160-baleen plates that are 50 cm in length and 25 cm in height. There are 40 bristles along the baleen plates with a medium gray color.
Habitat
Migration patterns allow Gray whales two distinct habitats. The
first is the summer feeding grounds in the plentiful Arctic waters of the Chuckchi
Sea. Here Gray whales are found in ice-free waters or in light ice cover with a
depth of 64 meters (Clarke 1989). Gray Whales stay in the feeding grounds for about
four months moving south in late September and early October (Watson 1981). The
second habitat is the breeding grounds off Baja California. There, Grays vacation in
the 71-degree waters where they give birth and keep the calves warm for enhanced
survival.
Natural History
Diet.
Migration patterns allow Gray whales two distinct habitats. The
first is the summer feeding grounds in the plentiful Arctic waters of the Chuckchi
Sea. Here Gray whales are found in ice-free waters or in light ice cover with a
depth of 64 meters (Clarke 1989). Gray Whales stay in the feeding grounds for about
four months moving south in late September and early October (Watson 1981). The
second habitat is the breeding grounds off Baja California. There, Grays vacation in
the 71-degree waters where they give birth and keep the calves warm for enhanced
survival.
Reproduction
Gray whales are not social animals,
interacting while passing on migration routes, feeding and breeding(Watson
1981). Therefore, courtship is complex and elaborate. In the
shallow lagoons during the month of January, mature male and female adults gather.
Spy hopping and circling are courtship rituals that begin in the early morning. By
midday whales break up into trios which consist of two males and one female. Both
males are involved in mating but the primary mate can be identified by one flipper held
motionless above the water as a signal(Watson 1981). The female approaches by
using delicate touch, caressing the male with her flippers until they lie belly to
belly(Watson 1981). The whales will stay together for up to an hour copulating
several times which can last up two minutes ending with a massive orgasmic
shudder (Watson 1981). While the mating is taking place, the second male is on
the far side of the female forming a prop or wedge to hold her next to her mate(Watson
1981).
Gestation will lasts twelve months so that the
calves are born in the same lagoons conceived in. Females give birth unattended in
waters about 33 feet deep. (Watson 1981) The Calf is nursed for 8 months with
the two leaving after two months beginning their long northward migration. The
calves are weaned in once they reach the Arctic waters.
Males reach puberty at eight years and will have a body length of
11 meters. Most males will have a marked seasonal reproduction cycle with a peak in
spermatogenetic activity in the early fall and winter (Rice 1984).
Dives and Breathing
There are two breathing patterns one used for
shallow and one for deep dives. During a shallow dive, less than 100 feet, Gray
whales breath 3-4 times at intervals of 10 to 20 seconds. Then, they dive for up to
3 to 4 minutes surfacing again about 1000 feet away. (Watson 1981). On a deep
dive, Grays take 5-6 breaths and dive for seven to ten minutes, surfacing 2,000 feet away
( Watson 1981). Gray Whales will spend 15% of their time at the surface, if left
undistributed they will rest on the surface up to half and hour basking in the sun.
When in the shallow lagoons, Grays will rest on the ocean floor in order to avoid the
harsh sun.
Parasites
From birth Gray whales receive harmless hitchhikers called barnacles
from their mothers. Along with barnacles, Gray whales will carry several species of
lice, Siamese scampi, Siamese respire, found only on Gray whales and Siamese yeti
commonly found. The lice will feed a pond Gray whale skin that is around open
wounds or scars. (Gordon 1991) Skin care for the Grays come by way of a silver
fish called the Topsmelt. Tposmelts supplement their diets on the lice for protein, and in
turn it decreases resistance and drag for the whales. (Gordon 1991)
Evolution
The earliest ancestors of whales lived on land
approximately 50 million years ago yet scientist have not been able to
identify the direct ancestors of modern Gray whales. Gray whales belong to the
orders of mammals called Cetaceans that include whales, porpoises, and dolphins.
(Gordon 1991) The Cetaceans contain 80 species all specifically adapted to
the marine environment. The Cetaceans have been divided to two major orders;
the tooth whales and the baleen whales or Odontoceti and Mysticeti orders.
From the Mysticeti there are three derived families, The Balaenidae ( right whales),
Eschrichtidae (gray whale), and Balaenopteridae (rorqual whale) (Watson 1981).
Mammals originally classified as Cetaceans first appeared
in the strata of the early middle Eocene period, they were primitive and less
adapted to a complete aquatic existence (Gaskin 1982). The first Cetaceans were in
the Archaeocti family which during the Oligocene Period (25-38 million years ago) they
split into four families Agorophiidae, Squalodontidae, the primitive oloocetes (tooth
whales), and the Aetiocetidae and Cetheriidae which are primitive Mysticeti(baleen whales)
(Evans 1987). The Odontocetes and Mysticetes evolved similarly from the Archaeocets
with a more aquatic mode of life, they had a backward shift of the external nostrils,
developed a structure to seal their nostrils against water, a long mobile neck, functional
hind limbs and a lost pelvic girdle. (Evans 1987) Their body also evolved in a
streamline manner with a dorsal fin (except gray whales) and horizontal tail flukes for
forward movement. (Evans 1987) By Mid-Oligocene the teeth of some Mysticetes
gave way to baleen plates, which were suspended from the ridges of the palate.
(Evans 1987) It is suggested thathe Zooplankton rich strata found in the Oligocene
favored the evolution of baleen mode of feeding. ( Evans 1987)
Gray Whales are the least specialized, giving scientists the best idea of what the first baleen whales may have looked( Watson 1981). A theory that Gray Whales evolved from Cetotheres was challenged because of the absence of fossil remains that linked the earliest modern Grays which are 50,000 to 120,000 years old to the much older Cetothere(Gordon 1991). The absence of fossils may be related in part to a coastal habitat in with carcasses beached leaving the bones to be scattered and broken rather than fossilized. (Evans 1987) Unfortunately, the origins of the Gray Whale are unknown since the oldest fossil date is from Pleistocene and are not easily distinguished from other species. (Evans 1987)
Distribution
Distribution Map of the Californian and Korean Stock
Eschrichtius robustus is distributed in a
continual coastal pattern. The North Atlantic stock is now extinct, but though
subfossil finds and with literacy evidence it is shown to have existed on both sides of
the North Atlantic and along the North American shores up till the seventeenth
century (Klinowska 1991). The North Pacific stock has two geographically isolated
populations; the California stock located in the Eastern North Pacific, and the
Korean stock located along the Western North Pacific coast. The Western stock
migrates from its winter calving grounds in Japan’s Northern Ikhotske Sea, to its
summer feeding grounds in Korean waters(Klinowska 1991). The Korean Stock has
a much smaller in population in comparisson to the Californian stock. It has
been hypothesized that they are displaced populations from the California stock (
Klinowska 1991). Because of the estimation that there are only 100-200 Gray
whales left, it is believed that the stock is going extinct and unfortunately little more
information is known.
The Eastern North Pacific or Californian stock contains the
largest population of Grey whales ranging from their feeding grounds in the Southern
Chuckchi Sea to their breeding grounds in the warm lagoons of Baja California(Reeves
1998). Before commercial whaling existed, the California stock flourished.
Population numbers were estimate30-40,000 with current population figures estimated
at around 20,000, with a 3.2% increase over 20 years(Klinowska 1991).
Migration Route for the Californian Stock
The California Gray Whale migrates along the coast
swimming between the Intertidal and Bathyl Zones which are located approximately 5- 100
meters off shore. They range in water temperatures between 41 and 70 degrees
Fahrenheit (Klinowaska 1991). During the 12,00 mile migration, Gray Whales
migrate between a longitude as far west as 130 degrees in August and as far east as
174 degrees in September. Grey whales never pass the Continental Shelf and their
entire migrating range is contained within 45 degrees of latitude (Reeves 1988).
EXPLOITATION
Eskimos living on the shores of the Northern Bering
Sea and the Chukchi Sea were the first to hunt Gray whales. Until 1969 the USSR on
the Chukotk coast were hunting large quantites of Grays, until the International Whaling
Commission set a cap at 179 per year, (mainly for Aboriginal hunting) (Rice, 1984).
The main culprits in the massive decline of Gray whale populations was American whaling
from 1846-1900’s (Rice, 1984). It was estimated from 1846-1874 that 8,100
Gray whales were hunted with the peak year of 474 whales taken ( Rice, 1984). In
1905 with modern whaling practices starting, began decrease of Grays hunted to 48 per year
until banned in 1937 by the International Convention for the Regulations of Whaling (Rice
1984).
Current threats to Gray whales are the commercial whale
watching boats in California and Mexico, as non-consumptive use of whales (Klinowska
1991). The pressure from visitors may disturb the whales especially in the breeding
lagoons. Also, Mitsubishi Cooperation and the Mexican Government in a joint
venture to build the worlds largest salt factory in Laguna San Ignacio, the last pristine
habitat of the Gray whale (www.savebajawhales.com)would endanger the habitat through noise
pollution, population growth, physical disturbance and secondary development (
www.savebajawhales.com ).
Bibliography
Clarke, J,E, Moore, D, Ljungblad. 1989. “Utilization patterns
in the north- eastern Chukchi Sea, July-October 1982-1987.” Canadian Journal
of Zoology. 67(11):2646-2654.
Evans, Peter. 1987. The Natural History of Whales and Dolphins. Helm, London.
Gaskin, D.E. 1982. The Ecology of Whales and Dolphins. Heinemann, London.
Gordon, David, Alan Baldridge. 1991. The Gray Whale. Monterey Bay Aquarium Press,
Monterey Bay.
Klinowska, Margaret. 1991. Dolphins, Porpoises and Whales on the World. IUCN.
Gland, Switzerland.
Reeves, Randall, Edward Michell. 1988. “ Current Status of the Gray Whale,
Eschrichtius robustus.” Canadian Field-Naturalist 84(3): 113-126.
Rice, Dale, Allen Wolfman, Howard Brattam. 1984. “ The Gray Whale, Eschrichtius
robustus.” US National Marine Fisheries Service Review 46(4):7-14.
Watson, Lyall. 1981. Sea Guide to Whales of the World. Dutton, New York.
http://www.savebajawhales.com.
http://www.bajasalt.com./GRAY/gray-1main.htlm.
send comments to bholzman@sfsu.edu
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