 Whales, dolphins, and porpoises are fascinating to many people. It may be because of their size or because they seem so playful. Much of this attention has been focused on human threats to these animals. These creatures of the sea are mammals just like humans. They breath air. They are warmblooded. They bear live young called calves which are nursed by their mothers.
The whales, dolphins, and porpoises are in an order known as cetaceans. All cetacean species are protected by the Marine Mammal Protection Act of 1972. In addition, there are currently seven species of cetaceans in U.S. waters that are protected under the Endangered Species Act. They are the blue whale, the bowhead whale, the fin whale, the humpback whale, the northern right whale, the sei whale and the sperm whale. All seven species are listed as endangered.
 These whales became endangered because of overexploitation by commercial whalers. During the 19th century, whales were hunted primarily for oil and baleen. Before the advent of electricity, many American homes were lighted with whale oil. As recently as twenty years ago, products from whales were used for products such as machine oil and women's cosmetics. Due to the passage of the Marine Mammal Protection Act in 1972 (MMPA), it became illegal to import into the United States products made from whales.
The effects that the MMPA has had on the status of marine mammals around the world is certainly immeasurable. In the United States, we have only begun to quantify the MMPA’s impact on marine mammal stocks. However, some tangible results can been recognized. Some species of marine mammals have recovered so well as to be removed from the List of Endangered and Threatened Widllife such as the eastern North Pacific stock of gray whale, which has the distinction of being the first marine mammal species to be removed from this list.
Unfortunately, there are some species of cetaceans on which scientists have spent much time and many resources attempting to recovery from decline and, despite considerable and often exhaustive, focused conservation efforts, and protection from hunting, these species remain critically endangered. The northern right whale, for which recovery efforts have included the study of life histories and the reduction of human-caused injury and mortality, among numerous other conservation and management actions. Still, the future of these species is uncertain. They number less than 400 animals and even in the best of circumstances, it may take a hundred years for the right whale population to recover because of their slow reproductive rate and the continued human threats from collisions with ships and entanglement in fishing gear.
SPECIES OF CETACEANS IN THE U.S. ON THE ENDANGERED SPECIES LIST
Biological data taken from: National Marine Fisheries Service, 1984. Marine Fisheries Review, "The Status of Endangered Whales." National Marine Fisheries Service, Scientific Publications Office, Seattle, Washington.
 Blue Whale: (Balaenoptera musculus) The blue whale is thought to be the largest animal ever to inhabit the earth. At one time it may have reached lengths of up to 31 meters (100 feet)--roughly the length of a basketball court (commercial hunting for the largest individuals has, over time, resulted in a decrease in their overall size). Blue whales have weighed up to 146 metric tonnes (160 tons). They feed on small shrimp-like crustaceans and can consume up to eight tons of krill a day. The loudest sound ever recorded from an animal was produced by a blue whale, and some scientists have speculated that they may be able to remain in touch with each other over hundreds of miles. The number of blue whales in the Southern Hemisphere was severely depleted by whaling to less than ten percent of its oiginal number.
 Bowhead Whale: (Balaena mysticetus) As with other species, the bowhead whale was severely depleted by commercial whaling. It may be as long as 18-20 meters (60-65 feet) and weigh as much as 109 metric tonnes (120 tons). The diet of bowhead whales is similar to that of right whales. They eat small crustaceans termed copepods and euphausiids (krill). Alaskan Eskimos still harvest about 50 bowheads each year for subsistence use.
Fin Whale: (Balaenoptera physalus) The fin whale is the second largest whale reaching lengths of up to 27 meters (88 feet) and weights up to 69 metric tonnes (76 tons). Depending on where they live, fin whales eat both fish and small crustaceans. In the Antarctic, their prey is almost exclusively krill, but in northern areas they often eat small schooling fish such as herring or anchovies. Like the other great whale species, fin whales were severely depleted by whaling.
Humpback Whale: (Megaptera novaeangliae) The humpback whale reaches a maximum length of about 15.6 meters (51 feet) and a maximum weight of about 34 metric tonnes (37.5 tons). In the Southern Hemisphere its primary food is krill, but in the Northern Hemisphere it eats schooling fish such as anchovies, cod, sand lance, and capelin. The humpback is one of the most popular whales for whalewatching on both the East and West Coasts. It is often photographed leaping out of the water--an activity called breaching. The humpback is also called the "singing whale" for their ability to produce complex, repeating "songs." A male's song may be as long as half an hour and changes slightly from year to year. Scientists estimate that there are 10,000 humpbacks worldwide--only about eight percent of its estimated initial population.
 Northern Right Whale: (Eubalaena glacialis) The right whale got its name because it was the "right" whale to hunt due to the facts that it often resting or "logged" at the surface, was slow moving, and floated after being killed. It is the most endangered species of whale in U.S. waters. It was the first whale hunted by American whalers and was so depleted that it has not recovered despite being protected from whaling for over 50 years. The maximum length of right whales is about 18.6 meters (60 feet), and the maximum weight is slightly more than 91 metric tonnes (100 tons). They feed on large schools of crustaceans, specifically copepods and krill and may feed on small fish near the ocean floor. Even though the threat of whaling has subsided, right whales still face the dangers of being entangled in fishing gear and being hit by ships.
Sei Whale: (Balaenoptera borealis) Sei whales can reach a length of 18.5 meters (60 feet) and a weight of 29.1 metric tonnes (32 tons). They feed primarily on krill and other small crustaceans, but also feed at times on small fish. The sei whale is the fastest of the baleen whales and can reach speeds of more than 33 km per hour (20 mph). Although less is known about the numbers of sei whales than some other species, they were also severely impacted by commercial whaling.
Sperm Whale: (Physeter macrocephalus) Unlike the other great whales on the endangered species list, the sperm whale does not feed with baleen, but is a toothed whale. It is the largest of the toothed whales, reaching a length of 18.5 meters (60 feet) in males and 12.5 meters (40 feet) in females. Sperm whales are noted for their ability to make deep dives, which can last up to an hour and a half and can be as deep as 3.3 kilomters (two miles) below the surface. It is the most abundant of all the endangered whales, with an estimated population of two million individuals, but due to dramatic declines caused by commercial whaling, they are still considered endangered. Sperm whales feed mainly on squid, including the giant squid.
Feeding Habits
As is indicated in the discussions of individual species, various species of whales feed at different levels on the food chain. Some species feed on the swarms of zooplankton (copepods and euphausiids, or "krill"), while others feed on schooling fish. The sperm whale feeds on squid, which themselves are predators. The type of prey a whale eats determine an individual species' foraging habits. Some are called lungers because they take huge gulps of water containing their prey, swallowing the prey and expelling the water. Others are skimmers that swim along with their mouths open before straining their prey from the water. One of the more interesting feeding methods has been observed in humpback whales. Alone or in group they sometimes form "bubble nets" around schools of fish, disorienting them with the bubbles and driving them into tighter groups, and then take turns swimming up through the bubble net to get their food.
Reproduction
Most whales have a very low reproductive rate: females only have a single calf every two to four years. With very small populations, this low rate of reproduction means that it may takes decades for some species to recover to their former population levels.
For some species of whales, the calves are born during the part of the annual cycle when the animals are in warmer waters, and the adults are not feeding. Unlike dolphins and porpoises, a calf spends a relatively short period of time with its mother. Calves usually become independent within a single year. During that time, a calf gains weight very rapidly. Whale milk is very rich, and a blue whale calf may gain almost 200 pounds per day.
Possible Threats to Recovery
Although commercial whaling currently no longer presents a threat to the survival of the baleen whales in U.S. waters, loss of habitat and other human activities may make recovery more difficult. Collisions with vessels, oil spills and other changes in water quality, coastal development, and increasing noise created from the use of oceanic resources may all affect the whales' lives.
Commerical fisheries may also affect whales as some whale species often become entangled in fishing gear. For example, each year several humpback whales are entangled in fishing gear along the east coast of the United States and Canada. Some fisheries may also compete with whales for food, such as herring.
One area of marine mammal science that is increasingly being focused on in the potential effects of anthropogenic (manmade) noise in the marine environment on marine mammals. Noise from seimic exploration, military exercises, and boat traffic may cause whales to alter their natural behavior. In fact, there is evidence that humpback whales in Hawaii may have changed their use of near-shore waters where calves are raised by their mothers because of increasing human activity and that migrating bowhead whales may move further offshore to avoid human-caused noise.
Although we do not have a full understanding of the possible impacts, pollution could also affect whales. Many contaminants can be stored in marine mammal blubber for long periods of time. Due to lives of feeding and fasting in which the larger whales lose large amounts of body fat, pollutant loads are usually lower in baleen whales than in dolphins and porpoises. Deterioration of the environment could possibly affect the whales in another way: if pollution and other factors reduce the number of fish and crustaceans, the food available to the whales could also be reduced.
Photo Credits (from top to bottom of page): NMFS file photo; NMFS file photo; Robyn Angliss, NMFS NMML: P. Michael Payne, Alaska Regional Office; and Center for Coastal Studies.
*Material on this web page courtesy of the U. S. Dept. of Commerce National Oceanic and Atmospheric Administration
NOAA Fisheries
National Marine Fisheries Service
Office of Protected Resources
URL http://www.nmfs.gov/prot_res/cetacean/cetacean.html
|
