Gray Whale

 

Status
ESA Endangered - Western North Pacific population
MMPA Depleted - Western North Pacific population
Delisted from ESA - Eastern North Pacific population

Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Eschrichtiidae
Genus: Eschrichtius
Species: robustus

Species Description
Gray whales are mysticetes, or baleen whales. Gray whales are the only species in the family Eschrichtiidae. These large whales can grow to about 50 ft (15 m) long, and weigh approximately 80,000 lb (35,000 kg). Females are slightly larger than males. They have a mottled gray body, with small eyes located just above the corners of the mouth. Their "pectoral fins" (flippers) are broad, paddle-shaped, and pointed at the tips. Lacking a dorsal fin, they instead have a "dorsal hump" located about two-thirds of the way back on the body, and a series of 8-14 small bumps, known as "knuckles," between the dorsal hump and the tail flukes. The tail flukes are more than 15 ft (3 m) wide, have S-shaped trailing edges, and a deep median notch. Calves are born dark gray and lighten as they age to brownish-gray or light gray. All gray whales are mottled with lighter patches, and have barnacles and whale lice on their bodies, with higher concentrations found on the head and tail.

Gray whales are frequently observed traveling alone or in small, unstable groups, although large aggregations may be seen on feeding and breeding grounds. Similar to other baleen whales, long-term bonds between individuals are rare. Gray whales are bottom feeders, and suck sediment and the "benthic" amphipods that are their prey from the sea floor. To do this, they roll on their sides and swim slowly along, filtering their food through coarse baleen plates, of which they have 130-180 on each side of the upper jaw. In doing so, they often leave long trails of mud behind them, and "feeding pits" in the sea floor.

Gray whales become sexually mature between 6-12 years, at an average of 8 years old. After 12-13 months of gestation, females give birth to a single calf. Newborn calves are approximately 14-16 ft (4.5-5 m) long, and weigh about 2,000 lb (920 kg). The average and maximum life span of gray whales is unknown, although one female was estimated at 75-80 years old after death (Jones and Swartz, 2002). The age of large whales in family Balaenopteridae can be estimated by counting the layers present in waxy ear plugs, which are formed in the auditory canal (Hohn 2002).

Killer whales (Orcinus orca) are the only non-human predator of gray whales.

Habitat
Gray whales are found mainly in shallow coastal waters in the North Pacific Ocean.

Gray Whale Range Map (click for larger view PDF)

Distribution
There are two isolated geographic distributions of gray whales in the North Pacific Ocean: the Eastern North Pacific stock, found along the west coast of North America, and the Western North Pacific or "Korean" stock, found along the coast of eastern Asia.

Most of the Eastern North Pacific stock spends the summer feeding in the northern Bering and Chukchi Seas, but gray whales have also been reported feeding along the Pacific coast during the summer, in waters off of southeast Alaska, British Columbia, Washington, Oregon, and California. In the fall, gray whales migrate from their summer feeding grounds, heading south along the coast of North America to spend the winter in their breeding and calving areas off the coast of Baja California, Mexico. Calves are born in shallow lagoons and bays from early January to mid-February. From mid-February to May, the Eastern North Pacific stock of gray whales can be seen migrating northward with newborn calves along the West Coast of the U.S.

Photo-identification studies indicate that gray whales in this stock move widely within and between areas on the Pacific coast, are not always observed in the same area each year, and may have several year gaps between re-sightings in studied areas (Calambokidis and Quan 1999, Quan 2000, Calambokidis et al. 2002).

Population Trends
Systematic counts of Eastern North Pacific gray whales migrating south along the central California coast have been conducted by shore-based observers at Granite Canyon most years since 1967. The most recent abundance estimates are based on counts made during the 1997/98, 2000/01, and 2001/02 southbound migrations, and range from about 18,000-30,000 animals. For more information, see the Stock Assessment Reports.

In contrast, the Western North Pacific population remains highly depleted and its continued survival is questionable. This population is estimated to include fewer than 100 individuals.

Threats
Commercial whaling severely depleted both the eastern and western populations between the mid-1800s and early 1900s. Beginning in the mid-1930s, gray whales were protected under a ban on commercial hunting adopted by the League of Nations. This ban (which included right whales) was the first international agreement to protect a whale species from commercial whaling operations. The ban on commercial gray whale catches has continued since the late 1940s under the International Whaling Commission. Gray whales are still hunted by native people of Chukotka and Washington State and are subject to catch limits under the International Whaling Commission's  "aboriginal subsistence whaling" scheme.

Other current threats include collisions with vessels, entanglement in fishing gear, habitat degradation, disturbance from ecotourism and whale watching, disturbance from low-frequency noise, and the possibility that illegal whaling or resumed legal whaling will remove animals at biologically unsustainable rates. The eastern stock's annual migration along the highly populated coastline of the western United States, and their concentration in limited winter and summer areas, may make them particularly vulnerable to impacts from commercial or industrial development or local catastrophic events.

Conservation Efforts
The Eastern North Pacific stock of gray whales was removed from the U.S. List of Endangered and Threatened Wildlife in 1994, based on evidence that they had recovered to near their estimated original population size and were not in danger of extinction throughout all or a significant portion of their range. In 1999, a NMFS review [pdf] of the status of the Eastern North Pacific stock of gray whales recommended the continuation of this stock's classification as non-threatened. This determination was based on the continued growth of the population (at that time, rising at 2.5% annually and estimated at 26,600 individuals) and the lack of evidence of any imminent threats to the stock. NMFS continues to monitor the abundance of the stock, especially as it approaches its carrying capacity.

The 2008 IUCN Red List of Threatened Species  lists gray whales as "least concern."

Regulatory Overview
All marine mammals, including gray whales, are protected under the Marine Mammal Protection Act of 1972, as amended. As of 1994, the Eastern North Pacific stock of gray whale is no longer listed as endangered under the Endangered Species Act of 1973.

The Western North Pacific stock of gray whales has not recovered. It is listed as "Endangered" under the ESA and "depleted" under the MMPA.