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Geologic Timeline: The last 144 million years of Earth's 4.6 billion year history.
Extinct gray whale.

FOSSIL FIELD GUIDE

As yet unnamed species
Extinct Gray Whale
Family: Eschrichtidae
Order Cetacea

Time
Pliocene Epoch

Place
It has only been found in the eastern Northern Pacific, thus far.

In Our Region
Chula Vista, San Diego, National City

Description
This extinct baleen whale discovered by the San Diego Natural History Museum paleontology staff reached about 35 feet (10 meters) in body length, and had a head shape similar to that of the modern gray whale. It had a narrow, delicate, and slightly arched rostrum. It is the most common Pliocene species of baleen whale found in southern California, out of some ten species of extinct baleen whales discovered in this area.

Although the whale is as yet unnamed, Tom Deméré, Curator of Paleontology, states that this whale is related to the modern gray whale, but is not in the same genus.

Skeleton of extinct gray whale.
Extinct gray whale
SDSNH specimen nos. 90517 and 90489

An Inside Look
Many fossils from this species of extinct gray whale have been found in the San Diego area by San Diego Natural History Museum paleontology staff. In fact, the department has seven skeletons of this species. The most complete is a beautiful juvenile whale skeleton, still articulated in a hard sandstone matrix. Many of the recovered fossil remains of this whale are juveniles, suggesting to paleontologists that the Pliocene San Diego Bay may once have been a calving lagoon, similar to those seen today in areas of Baja California, such as San Ignacio and Scammon's lagoons.

Ecology
The following is information about Eschrichtius robustus, the living species of gray whale. We cannot be certain if the extinct gray whale had similar patterns of feeding, reproduction, or lifestyle.

The living gray whale, up to 45 feet (13.7 meters) long, is a bulk filter feeder with a streamlined body, tapered head, and 2-5 short grooves along the throat. Instead of teeth, like all baleen whales, the gray whale has fine keratin tubules that hang from the roof of the mouth in cornified plates.

With these baleen sieves, gray whales trap minute organisms by rolling to one side on the ocean floor and sucking in mud, water and tiny invertebrates from the substrate, and pressing out the water with their tongue. They are the only baleen whale that "mines" the ocean bottom in this manner. Long scours in the mud attest to their benthic foraging habits. Small crustaceans called amphipods make up a large portion of their diet.

The gray whale finds most of its food in the mud or sand of shallow sea floors, along the Pacific coastline. These whales migrate from the cold waters of Alaska and Siberia all the way to the breeding lagoons in Baja California. Heavily depleted during the intense whaling industry of the 1800s-1900s, almost to extinction, this species has since bounced back, thanks to environmental protection laws.

Gray whales are covered with a thick layer of blubber that serves to reduce drag in the water, acts as an energy reservoir to store fat, and insulates against cold water temperatures. The species is restricted to coastal areas because of its bottom feeding diet, and is found inshore or offshore in shallow continental shelf waters.

Gray whales do all their feeding in summer and fall in high latitudes, feeding heavily from May through October, storing fat reserves. During this time, the pack ice retreats, exposing the sea floor to daylight, which in turn causes a bloom of microorganisms.

During the rest of year polar feeding grounds are covered with ice, so the whales migrate to warm winter breeding grounds. During the migration, the whales fast for 6 months or so, losing about 30% of their body weight.

Breeding starts most often in late November and December during the migration south. Gestation lasts about a year. A single calf is born, weighing up to1500 pounds (680 kg).


Head of modern gray whale.

Gray whale and calf.

The mother whale is fiercely protective of her baby, often stroking it. The baby whale nurses while at the lagoons and on migration, always staying close to its mother. The milk is very rich, made up of 53 % fat .Calves are weaned at about 8 months of age. The long return migration north starts in February.

These animals were once called "devil fish" by whalers who harpooned the whales and witnessed their ferocious attempts to defend their young. Now that they are protected, some gray whales are known to be very friendly and curious and seek out physical contact with humans.

Their skin has large gray and white patches, and is covered with scarred areas and parasites; in fact they have more ectoparasites than any other cetacean. Their lifespan is unknown, although it is perhaps 80 years or so.

The North Atlantic population of gray whales is now extinct. Sub-fossils, so called because they are less than 10,000 years old, have been found on the east coast from New Jersey to Florida, the most recent dating to 1650 AD. The demise of this population was most likely due to whaling.

A Korean or western north Pacific population of gray whales is very close to being eliminated also, most likely due to whaling. The eastern north Pacific population is by far the largest surviving group, and probably amounts to about 20,000 individuals.

The gray whale was listed as an endangered species in 1969 by the Federal government. After making a comeback many years later, it has been de-listed. However, there is concern about warming trends in Arctic waters, since this may result in a sudden decrease of food resources. An increase in mortality in 1999 and 2000 seemed to indicate some gray whales were starving.

This species continues to be threatened by virtue of the fact that they are coastal animals, and therefore closely connected with ship traffic, pollution, and oil and gas extraction.

Further Investigation
The evolutionary history of the modern gray whale has been a mystery. However, the discovery and study of the new eschrichtiid fossils from the San Diego area provides strong evidence that gray whales (fossil and modern) are closely related to the balaenopterid baleen whales (fin and humpback whales). Molecular studies using DNA support this hypothesis and suggest that the family evolved here in the north Pacific Ocean during the Pliocene Epoch. The gray whale is very distinct and placed in its own family. Further studies of this species of extinct gray whale will help to flesh out the story of diversity in this family.

Suggested Reading
Perrin, William F., Bernd Wursig and J.G. M. Thewissen. 2002. Encyclopedia of Marine Mammals. San Diego: Academic Press.



Text: Margaret Dykens and Lynett Gillette
Illustration: William Stout
Fossil whale photograph: François Gohier
Gray whale photographs: Jon Rebman



Pleistocene Epoch 1.8 million-10,000 years ago.
Pliocene Epoch 5-1.8 million years ago.
Miocene Epoch 24-5 million years ago.
Oligocene Epoch 34-24 million years ago.
Eocene Epoch 53-34 million years ago.
Paleocene Epoch 65-55 million years ago.
Cretaceous/Tertiary Boundary Rock, 65 million years ago.
Cretaceous Period 144-65 million years ago.
Earth's history began 4.6 billion years ago.
MYA = million years ago.