Rorquals: Balaenopteridae

views updated

RORQUALS: Balaenopteridae

BLUE WHALE (Balaenoptera musculu): SPECIES ACCOUNTS


Rorquals (ROAR-kwulz) are large baleen (buh-LEEN or BAY-leen) whales. Like all baleen whales, they are filter feeders. These whales do not have teeth. Instead, they have many overlapping plates called baleen plates that hang like a curtain from the upper jaw. These plates are made of a material called keratin (KARE-ah-tin). This horny, fingernail-like material frays out into thin hairs at the end of each strand to make a strainer. Rorquals also have a set of ridges and groves along the bottom of their mouth and throat. When they open their mouth to feed, the grooves expand and make the inside of their mouth very large so that they can suck up a lot of water. They then push the water out through the baleen plates and use their tongue to lick up food that remains.

Rorqual whales can be anywhere between 32 to 102 feet (10 to 31 meters) long and weigh as much as 200 tons (181 metric tons). Some rorquals have a dorsal fin on their backs, and others have particular bumps or ridges on their head and back that help to distinguish them from other rorquals. Females are usually larger than males.


Rorquals are found in all of the oceans of the world and the seas that connect to these oceans. They do not live in the parts of the Arctic and Antarctic Ocean that are covered by ice, since they must come to the surface to breathe. Rorquals are more often found in shallower parts of the ocean that are closer to land. These areas are called continental shelves.


Rorquals can be seen most often in open waters over continental shelves. They can sometimes be found in bays and inlets near land.


Rorqual whales eat small fish, squid, and other small marine animals. Much of their diet is made up by krill, which are tiny shrimp-like animals. They obtain their food by filtering large quantities of water through their baleen. Normally they feed at depths no greater than 300 feet (91 meters) and stay under water no longer than ten minutes.

To capture the large amount of food that they need, rorquals expand their mouth and open it wide. Then they close their mouth most of the way, leaving only the baleen exposed, like a sieve (siv) between their lips, and squeeze the water out by ramming their tongue against the baleen. This pushes out the water and leaves the food behind. The blue whale, the largest rorqual, can eat 8 tons (7.3 metric tons) of krill per day.


Rorquals normally swim at around 10 to 20 miles per hour (16 to 32 kilometers per hour). Some species, such as the fin whale can swim at speeds of 23 miles per hour (37 kilometers per hour) for short periods. Groups, or pods, are usually made up of two to five individuals, but sometimes large groups of rorquals come together where food is abundant. Generally rorquals do not dive deeper than 300 feet (91 meters) below the surface.

Even though different rorqual species live in different parts of the world, they all follow a migration pattern. This means that they spend part of the year in a warmer area and then move, often over great distances, to a cooler area for the other part of the year. Rorquals time their reproduction with this yearly cycle by giving birth in the warmer area and feeding in the cooler area. A female rorqual is pregnant for about a year, depending on the species, before she gives birth to a single calf. When the calf is born, it measures between 9 and 23 feet (2.7 and 7 meters) long. The young nurse, feed on their mother's milk, for about a year and grow rapidly. They become mature between five and fifteen years and live, on average, fifty to eighty years.


All species of rorquals have been hunted by people for their oil and meat. Their oil was used in making margarine, soap, and lubricants, or industrial oils, until the 1980s. During the early 1900s humpback whales were hunted heavily, because they live close to land and their population was severely reduced. Hunters then began hunting of a number of other rorqual species. The blue whale became a preferred target of whalers, whale hunters, because of its size and the quantity of oil, meat, and blubber that it could provide. Larger blue whales could contain as much as 9,000 gallons (34,000 liters) of oil. Through efforts of the International Whaling Commission, environmental groups and other agencies, large scale commercial whaling ended by 1990. Today, whale watching is more popular and profitable than hunting. According to the World Wildlife Fund, this ecotourism, travel for the purpose of observing wildlife and learning about the environment, generated approximately one billion dollars in 2000.


Scientists have discovered that each humpback whale's dorsal, back, fin and tail markings are unique. This is the whale's fingerprint. Knowing this, scientists can follow individual whales by photographing them when they leap out of the water and matching their fin and tail pattern to known individual whales. Being able to track a single whale has helped scientists learn where they migrate, when they mate, how long they live, and other important information.


The International Whaling Commission, set up in 1946 by twenty countries, has attempted to monitor and establish limits on the number of whales and the kinds of whales that are killed each year. In 1972, the United States Congress passed the Marine Mammal Protection Act banning hunting of marine mammals and the purchasing of their products from other countries. While these efforts have brought an end to most whale hunting worldwide, they may have been too late for many rorqual species. Today, the blue whale, the sei whale, and the fin whale are considered Endangered, facing a very high risk of extinction in the wild. Humpback whales are considered Vulnerable, facing a high risk of extinction in the wild. Studies done by the International Whaling Commission have estimated that there are fewer than five hundred blue whales remaining in the world.

BLUE WHALE (Balaenoptera musculu): SPECIES ACCOUNTS

Physical characteristics: The blue whale is the largest animal on the planet. Their skin is gray or blue-gray with lighter colored splotches. Blue whales grow to between 74 and 79 feet (23 and 24 meters) and weigh up to 200 tons (181 metric tons). Females are slightly larger than males.

Geographic range: Blue whales are found in all oceans worldwide.

Habitat: Blue whales spend the spring months in the colder waters close to the poles, but migrate toward the warmer regions closer to the equator for the other eight months.

Diet: Blue whales eat only during the spring for about four months when they feed in colder waters. The rest of the year, they live off stores of blubber, fat, that they build up during the feeding season. Blue whales eat krill and generally avoid other marine life. When they are feeding, they can eat 8 tons (7.3 metric tons) of krill per day.

Behavior and reproduction: Although they usually swim at about 14 miles per hour (22 kilometers per hour), blue whales have been

known to swim as fast as 30 miles per hour (48 kilometers per hour). They dive for ten to twenty minutes to feed and generally do not dive more than 300 feet (91 meters) below the surface. Female blue whales give birth in late spring and summer after twelve months of pregnancy to young that are about 23 feet (7 meters) long. Blue whales can live past one hundred years of age.

Blue whales and people: When whalers began using ships that allowed them to haul up whales no matter how large they were, the blue whale populations dropped dramatically. Because of their size, blue whales were highly prized, as whalers could bring in large amounts of oil, blubber, and meat with a single kill. During the years of 1930 and 1931, almost 30,000 blue whales were killed. During the 1960s, the blue whale gained protection from the International Whaling Commission. The blue whale may not survive much longer. Some scientists predict that the remaining population of about five hundred whales is not large enough to support a recovery. In recent decades the blue whale has taken a place in popular culture, and its image has helped to promote conservation efforts and ecotourism activities such as whale watching.

Conservation status: Blue whales are Endangered. ∎


Physical characteristics: The northern minke whale is the smallest rorqual whale, but is still between 26 and 33 feet (8 and 10 meters) long. They are sleek whales with black, brown or gray backs and lighter bellies. They have light stripes across their flippers.

Geographic range: Northern minke whales migrate from tropical waters to the polar oceans in the Northern Hemisphere. There are two separate populations, one in the North Atlantic and one in the North Pacific.

Habitat: Northern minke whales live at the edge of the polar ice fields, and sometimes even enter the fields of ice. They prefer water close to shore, and will enter bays and inlets.

Diet: Although a large part of their diet is krill and small schooling fish, the northern minke whale feeds on many foods that other rorquals generally avoid, including larger fish such as salmon, cod, and mackerel.

Behavior and reproduction: Northern minke whales are most often seen alone, in pairs, or groups of three. However, there are times when they gather in large groups of up to fifty in rich feeding areas. Female northern minke whales are pregnant for ten months, after which the calves nurse for about six months. Calving usually occurs in the winter. Calves stay with their mothers for about two years, even when they have stopped nursing. These rorquals often live to be sixty years old.

Northern minke whales and people: Meat from this rorqual, as well as many other rorquals, is sought after in Japan and Korea as a special delicacy. Their meat is extremely expensive. Despite the International Whaling Commission's 1986 ban on hunting, these whales are still taken illegally because of the high price their meat brings.

Conservation status: Northern minke whales, unlike many of their fellow rorquals, are abundant and considered at low risk for extinction. ∎


Physical characteristics: Humpback whales grow to between 38 and 49 feet (12 to 15 meters) in length and weigh between 27 and 33 tons (25 to 30 metric tons). The tail can be 18 feet (5.5 meters) wide. They are black except for their underside, flippers, and throat, which are white. Their head, jaw, and flippers are covered with bumps. Each bump has at least one hair growing out of it. Scientists do not know what these bumps or hairs are for. The humpback whale has the longest flippers of any whale.

Geographic range: Humpback whales live in the Pacific and Atlantic Oceans.

Habitat: Humpback whales spend the cooler months closer to the equator and then migrate towards the north or south pole for the warmer months.

Diet: Like most rorquals, humpback whales eat krill or small marine animals that they catch by filtering large quantities of water through their baleen. While the largest part of their diet is krill, the humpback whale also eats a variety of small fish. Each whale eats about 1.5 tons (1.4 metric tons) of food a day.

Behavior and reproduction: Humpback whales tend to gather in groups of two to five. Not only are they known for their acrobatic

ability to leap out of the water and slap the water with their tail and flippers, but humpback whales do some of the most complex and intricate singing of any mammal. These songs last about twenty to thirty minutes and are repeated for hours. The North Atlantic whales all sing the same song, and it is different from the song the North Pacific humpback whales sing. Females are pregnant for twelve months and nurse their young for another year after birth. They usually have a new calf every other year. Humpback whales can live up to seventy-five years.

Humpback whales and people: Because humpback whales tend to stay closer to the land than other rorquals, they were hunted heavily. Although their numbers have decreased substantially, the humpback whale is less likely to go extinct than several other whales.

Conservation status: Humpback whales are considered Vulnerable. ∎



Clapham, Phil. Humpback Whales (World Life Library). Stillwater, MN: Voyageur Press, 1996.

Cooper, Jason. Baleen Whales. Vero Beach, FL: The Rourke Book Company, 1996.

Miller-Schroeder, Patricia. Blue Whales. Austin, TX: Raintree Steck-Vaughn, 1998.

Web sites:

American Cetacean Society. (accessed on July 8, 2004).

International Whaling Commission. (accessed on July 8, 2004).

Myers, Phil. "Family Balaenopteridae (Rorquals)." Animal Diversity Web. (accessed on July 9, 2004).

Whale and Dolphin Conservation Society. (accessed on July 8, 2004).