HABITAT & DISTRIBUTION OF BALEEN WHALES

DISTRIBUTION
1.

Baleen whales can be found in all oceans worldwide, from polar seas to temperate and tropical zones.

2.

Some species of baleen whales have limited distribution. For example:
•

Southern right whales (Eubalaena australis) are found only in the southern hemisphere; northern right whales (Eubalaena glacialis) are found only in the northern hemisphere.
• Bowhead whales (Balaena mysticetus) inhabit the waters around the Arctic ice edges that melt and reform seasonally.
• Some populations of baleen whale species are resident to restricted areas. A population of fin whales (Balaenoptera physalus) is found year-round in the Gulf of California.

3.

Some species are found throughout the world. For example, fin whales, minke whales (Balaenoptera acutorostrata), sei whales (Balaenoptera borealis), blue whales (Balaenoptera musculus), and humpback whales (Megaptera novaeangliae) have worldwide distributions. Bryde's whales (Balaenoptera edeni) are found throughout the tropics and subtropics.
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HABITAT
1.

Some baleen whales are coastal. (They stay near shore.) They forage along the productive continental shelf area. Some species give birth and rear young in protected coastal bays and lagoons. Other species are oceanic. (They roam the open seas.)
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MIGRATION
1.

Most baleen whales are highly migratory, moving toward high-latitude (polar) feeding areas in the summer and toward low-latitude (tropical) calving areas in the winter.
•

Variations in water temperature, food availability, and feeding habits may account for movements of some animals.
• Some individual whales do not migrate. These may be juveniles or post-reproductive adults and may stay in protected nearshore areas.

2.

Northern and southern hemisphere populations of the same species don't encounter one another due to the opposite seasons in the northern and southern hemisphere. While the northern population is breeding and calving in tropical regions during the northern hemisphere's winter, the southern population is foraging in polar feeding grounds during the southern hemisphere's summer.

3.

Many factors may act as environmental cues to help baleen whales navigate along a migration route: sun orientation, topography of the ocean floor, water temperature, chemical changes in the water, and magnetic sensing. Satellite-tracking studies assist scientists researching migratory behavior of baleen whales.

4.

Most baleen whales migrate 3,000 to 5,000 km (1,800-3,000 miles) each way, depending on the species.
•

Gray whales migrate more than 10,000 km (6,000 miles) each way - the longest known migration for any mammal.
• Some species migrate much shorter distances. For example, Bryde's whales only move from temperate regions to the equator. And sei whales don't migrate as far toward the poles as most species do.
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POPULATION
1.

For most baleen whale species, estimating abundance is difficult due to their vast distribution and their aquatic habits.

2.

For many species, there are no population estimates. For others, estimates are based on old data that may no longer reflect the current population. The table below lists the most current estimates available.

3.

As a management tool, scientists categorize a geographically isolated and genetically distinct group of whales as a whale stock. Thus, a species may be represented by several stocks. For some species, certain stocks are depleted, while worldwide population numbers remain high.
•

More than 800,000 minke whales are found worldwide, yet scientists consider the West Greenland stock depleted.
• Most of the total current population of bowhead whales survives in only one of five stocks. The other four face extinction.
• Certain stocks are recovering due to international protection from commercial whaling. Most notably, the gray whale population appears to have reached pre-whaling numbers.
• Photo-identification of individual whales helps researchers monitor the size of certain populations. Experts photograph and catalog scars and other natural markings on the flukes, dorsal fins, and flanks of individual whales. When these identified whales are re-sighted during subsequent years, researchers can gather information on reproductive and growth rates, differences between males and females, and migration.
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TABLE: BALEEN WHALE DISTRIBUTION & ABUNDANCE

FAMILY BALAENIDAE: THE RIGHT WHALES

SPECIES
DISTRIBUTION ABUNDANCE


bowhead whale
(Balaena mysticetus)
Bering-Chukchi-Beaufort Seas 8,000
Sea of Okhotsk probably 10's to a few 100's in each of these populations
Davis Strait
Hudson Bay
Greenland Sea


pygmy right whale
(Caperea marginata)
southern hemisphere unknown


Southern right whale
(Eubalaena australis)
southern hemisphere 4,300


Northern right whale
(Eubalaena glacialis)
North Pacific

possibly several hundred
North Atlantic

FAMILY BALAENOPTERIDAE: THE RORQUAL WHALES

SPECIES
DISTRIBUTION ABUNDANCE


minke whale
(Balaenoptera acutorostrata)
southern hemisphere 761,000
North Atlantic 149,000
western North Pacific 25,000
rest of North Pacific unknown


sei whale
(Balaenoptera borealis)
southern hemisphere 37,000
North Pacific 14,000
North Atlantic probably few 1,000's


Bryde's whale
(Balaenoptera edeni)
western North Pacific 14,000
rest of northern hemisphere unknown
southern hemisphere unknown


blue whale
(Balaenoptera musculus)
southern hemisphere

400-1,400
California, Oregon, Washington 1,480
rest of northern hemisphere unknown


fin whale
(Balaenoptera physalus)
North Atlantic 47,300
California, Oregon, Washington 3,200
rest of northern hemisphere unknown
southern hemisphere 103,000


humpback whale
(Megaptera novaeangliae)
western North Atlantic 11,570
rest of northern hemisphere unknown
southern hemisphere south of 60˚S 10,000
rest of southern hemisphere unknown

FAMILY ESCHRICTIDAE: THE GRAY WHALE

SPECIES
DISTRIBUTION ABUNDANCE


gray whale
(Eschrictius robustus)
eastern North Pacific 26,000
western North Pacific less than 100