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 while others are found throughout the world.
a. Certain species are limited to specific environmental zones. Southern right whales are only found in the southern hemisphere. Bowhead whales inhabit the waters around the Arctic ice edges that melt and reform seasonally.
b. Blue, sei, fin, Minke, and humpback whales have worldwide distributions.
c. Bryde's whales are found throughout the tropics and subtropics.
d. Some populations of baleen whale species are resident to restricted areas. A
population of fin whales is found year-round in the Gulf of California.
1. Some baleen whales are coastal (they stay near the shore) and others are oceanic (they roam the open seas).
2. Some species give birth and rear young in protected coastal bays and lagoons.
3. Some species forage along the productive continental shelf area.
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.
a. Migrations for most baleen whales average 3,000 to 5,000 km (1,800-3,000 mi.) each way, depending on the species.
b. Gray whales migrate over 10,000 (6,000 mi.) each way--the longest known migration for any mammal. See population.
c. Other 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 towards the poles as most species do.
d. Northern and southern hemisphere populations of the same migratory species don't encounter one another due to the opposite seasons. The northern population is feeding in the polar region while the southern population is breeding and calving in the tropical region.
e. Many factors may act as environmental cues to help baleen whales navigate along a migratory route: sun orientation, topography of the ocean floor, water temperature, chemical changes in the water, and magnetic sensing. Satellite-tracking studies assist scientists in research on migratory behavior of baleen whales.
2. Some individual whales do not migrate. These may be juveniles or post-reproductive adults and may stay in protected nearshore areas.
3. Variations in water temperature, food availability, and feeding habits may account for movements of some animals.
Gray whales migrate annually, making a 20,000-km (12,000-mile) round-trip journey from arctic feeding grounds to calving lagoons in Baja California, Mexico.
1. As a management tool, scientists catagorize a whale stock as a geographically isolated and genetically distinct group of whales. Thus, a species may be represented by several stocks. Some stocks of baleen whales are depleted, while worldwide population numbers remain high.
a. More than 800,000 Minke whales are found worldwide, yet scientists consider the West Greenland stock depleted.
b. About 95% of the total current population of bowhead whales survives in only one of four stocks. The other three face extinction.
c. Certain stocks are recovering due to international protection from commercial whaling. Theeastern Pacific gray whale was removed from the Endangered Species List in 1993 because the population (about 21,000 in 1993) appears to have reached pre-whaling numbers.
2. Photo-identification of individual whales allows reseachers to monitor the size of certain populations. Scars and other natural markings on the flukes, dorsal fins, and flanks of individual whales are photographed and catalogued. 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. See also callosites.
3. Population estimates of baleen whale species.
SeaWorld/Busch Gardens Animal Information Database
www.seaworld.org / www.buschgardens.org
©2002 Busch Entertainment Corporation.
All Rights Reserved.