Humpback Whale

NOAA

 

Status
ESA Endangered - throughout its range
MMPA Depleted - throughout its range

Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Balaenopteridae
Genus: Megaptera
Species: novaeangliae

Species Description
Humpback whales are well known for their long "pectoral" fins, which can be up to 15 feet (4.6 m) in length. Their scientific name, Megaptera novaeangliae, means "big-winged New Englander" as the New England population was the one best known to Europeans. These long fins give them increased maneuverability; they can be used to slow down or even go backwards.

Similar to all baleen whales, adult females are larger than adult males, reaching lengths of up to 60 feet (18 m). Their body coloration is primarily dark grey, but individuals have a variable amount of white on their pectoral fins and belly. This variation is so distinctive that the pigmentation pattern on the undersides of their "flukes" is used to identify individual whales, similar to a humans fingerprint.

Humpback whales are the favorite of whale watchers, as they frequently perform aerial displays, such as breaching (jumping out of the water), or slap the surface with their pectoral fins, tails, or heads.

In the summer, humpbacks are found in high latitude feeding grounds such as the Gulf of Maine in the Atlantic and Gulf of Alaska in the Pacific. In the winter, they migrate to calving grounds in subtropical or tropical waters such as the Dominican Republic in the Atlantic and the Hawaiian Islands in the Pacific. The Arabian Sea humpback, however, does not migrate, remaining in tropical waters all year.

Humpback whales travel great distances during their seasonal migration, the farthest migration of any mammal. The longest recorded migration was 5,160 miles (8,300 km). This trek from Costa Rica to Antarctica was completed by seven animals, including a calf. One of the more closely studied routes is between Alaska and Hawaii, where humpbacks have been observed making the 3,000 mile (4,830 km) trip in as few as 36 days.

During the summer months, humpbacks spend the majority of their time feeding and building up fat stores (blubber) that they will live off of during the winter. Humpbacks filter feed on tiny crustaceans (mostly krill), plankton, and small fish and can consume up to 3,000 pounds (1360 kg) of food per day. Several hunting methods involve using air bubbles to herd, corral, or disorient fish. One highly complex variant, called "bubble netting," is unique to humpbacks. This technique is often performed in groups with defined roles for distracting, scaring, and herding before whales lunge at prey corralled near the surface.

In their wintering grounds, humpback whales congregate and engage in mating activities. Humpbacks are generally "polygynous" with males exhibiting competitive behavior on wintering grounds. Aggressive and antagonistic behaviors include chasing, vocal and bubble displays, horizontal tail thrashing, and rear body thrashing. Males within these groups also make physical contact; striking or surfacing on top of one another. These bouts can cause injuries ranging from bloody scrapes to, in one recorded instance, death. Also on wintering grounds, males sing complex songs that can last up to 20 minutes and be heard 20 miles (30 km) away. A male may sing for hours, repeating the song several times. All males in a population sing the same song, but that song continually evolves over time. Humpback whale singing has been studied for decades, but scientists still understand very little about its function.

Gestation lasts for about 11 months. Newborns are 13 to 16 ft (4 to 5 m) long and grow quickly from the highly nutritious milk of their mothers. Weaning occurs between 6 and 10 months after birth. Mothers are protective and affectionate towards their calves, swimming close and frequently touching them with their flippers. Males do not provide parental support for calves. Breeding usually occurs once every two years, but sometimes occurs twice in three years.

Habitat
During migration, humpbacks stay near the surface of the ocean.

While feeding and calving, humpbacks prefer shallow waters. During calving, humpbacks are usually found in the warmest waters available at that latitude. Calving grounds are commonly near offshore reef systems, islands, or continental shores.

Humpback feeding grounds are in cold, productive coastal waters.

Humpback Whale Range Map (click for larger view PDF)

Distribution
Humpback whales live in all major oceans from the equator to sub-polar latitudes.

In the western North Atlantic ocean, humpback whales feed during spring, summer, and fall over a range that encompasses the eastern coast of the United States (including the Gulf of Maine), the Gulf of St. Lawrence, Newfoundland/Labrador, and western Greenland. In winter, whales from the Gulf of Maine mate and calve primarily in the West Indies. Not all whales migrate to the West Indies every winter, and significant numbers of animals are found in mid- and high-latitude regions at this time.

In the North Pacific, there are at least three separate populations:

1. California/Oregon/Washington stock winters in coastal Central America and Mexico and migrates to areas ranging from the coast of California to southern British Columbia in summer/fall;
2. Central North Pacific stock winters in the Hawaiian Islands and migrates to northern British Columbia/ Southeast Alaska and Prince William Sound west to Kodiak; and
3. Western North Pacific stock winters near Japan and probably migrates to waters west of the Kodiak Archipelago (the Bering Sea and Aleutian Islands ) in summer/fall. There is some mixing between these populations, though they are still considered distinct stocks.

In the Southern Hemisphere, the International Whaling Commission (IWC) has designated seven major breeding stocks linked to seven major feeding areas. Most breeding areas for Southern Hemisphere humpbacks are at 20°S, although some are in the Northern Hemisphere, including areas along the west coast of Africa and Central America. In Costa Rica, there is overlap with Northern Hemisphere humpbacks geographically, but they are not there at the same time. All Southern Hemisphere humpbacks share feeding grounds in the Antarctic south of 40°S and between 120°E and 110°W.

Population Trends
Humpbacks are increasing in abundance in much of their range.

In the Southern Hemisphere, humpback abundance prior to commercial exploitation is estimated at 100,000 whales. Including illegal unreported Soviet whaling, there were an estimated 200,000 Southern Hemisphere humpback whales harvested from 1904-1980. The current Southern Hemisphere population may be over 25,000 whales although we have little data on which to base this estimate.

In the North Pacific, humpback abundance was estimated at fewer than 1,400 whales in 1966, after heavy commercial exploitation. The current abundance estimate for the North Pacific is about 20,000 whales.

For the North Atlantic, the best available estimate is 11,570 whales.

No current or historical abundance estimates are available for humpbacks in the Indian Ocean.

While estimating humpback whale abundance is inherently difficult, the best estimates for minimum populations for the five stocks of humpback whales recognized in U.S. waters are:

1. Gulf of Maine stock in the Atlantic Ocean - about 550
2. Western North Pacific - about 365
3. Central North Pacific (including the Southeast Alaska feeding area) - about 3,700
4. California/Oregon/Washington - about 1,250
5. American Samoa - about 150

The Gulf of Maine, central North Pacific, and California/Oregon/Washington stocks seem to be increasing.

There is not enough information to accurately assess population trends for the western North Pacific and American Samoa stocks.

Threats
Humpback whales face a series of threats including entanglement in fishing gear (bycatch), ship strikes, whale watch harassment, habitat impacts, and proposed harvest.

Humpbacks can become entangled in fishing gear, either swimming off with the gear or becoming anchored. NOAA Fisheries has observed "incidental take" of humpback whales in the California/Oregon swordfish and thresher shark drift gillnet fishery. Potential entanglement from gear from several fisheries can occur on their long migration from Hawaii to Alaska. Humpbacks in Hawaii have been observed entangled in longline gear, crab pots, and other non-fishery-related lines.

Inadvertent ship strikes can injure or kill humpbacks. NOAA Fisheries has verified mortality related to ship strikes in the Gulf of Maine and in southeastern Alaska. Ship strikes have also been reported in Hawaii.

Whale watching vessels may stress or even strike whales. The Gulf of Maine stock is the focus of whale watching in New England from late spring to early fall, particularly within the Stellwagen Bank National Marine Sanctuary. The central North Pacific stock is the focus of a whale-watching industry on their wintering grounds in the Hawaiian Islands. The feeding aggregation in southeast Alaska is also the focus of a developing whale-watching industry that may impact whales in localized areas.

Shipping channels, fisheries, and aquaculture may occupy or destroy humpback whale aggregation areas. Recreational use of marine areas, including resort development and increased boat traffic, may displace whales that would normally use that area. In Hawaii, acoustic impacts from vessel operation, oceanographic research using active sonar, and military operations are also of increasing concern.

While there is no current legal commercial harvest of humpback whales, there is interest by some countries to resume humpback harvest. Japan has proposed killing 50 humpback whales as part of its program of scientific research under special permit (scientific whaling) called JARPA II in the IWC management areas IV and V in the Antarctic . Also, Denmark recently proposed a hunt of 10 humpbacks a year off the coast of Greenland. Both of these proposed harvests have the potential to negatively impact recovery of humpback whales.

Conservation Efforts
The most recent conservation efforts by NOAA Fisheries and its partners are to:

• Reduce bycatch in gillnet and trap/pot fisheries in the western North Atlantic through the Atlantic Large Whale Take Reduction Plan.
• Implement marine mammal take reduction measures identified in the Pacific Offshore Cetacean Take Reduction Plan.
• Mitigate ship strikes and respond to humpback whales in distress (see Alaska and Hawaii regulations).
• Educate whale watch vessels and boat operators on practicing safe boating around whales.
• Monitor humpbacks in U.S. waters via shipboard surveys and mark recapture studies.
• Research humpback population structure and abundance including the Structure of Populations, Levels of Abundance, and Status of Humpbacks (SPLASH) and More North Atlantic Humpbacks (MoNAH) projects as well as work done at the Hawaiian Islands Humpback Whale National Marine Sanctuary.

In 1991, NOAA Fisheries published the humpback whale recovery plan [pdf].

Regulatory Overview
In 1946, the International Convention for the Regulation of Whaling regulated commercial whaling of humpback whales. In 1966, the International Whaling Commission prohibited commercial whaling of humpbacks. In June 1970, humpback whales were designated as "endangered" under the Endangered Species Conservation Act (ESCA). In 1973, the Endangered Species Act (ESA) replaced the ESCA, and continued to list humpbacks as endangered.

In 1972, humpbacks were provided additional protection under the Marine Mammal Protection Act (MMPA), and were considered "depleted" in 1973. Under the MMPA, threats to humpbacks are mitigated by regulations implementing the Pacific Offshore Cetacean Take Reduction Plan and the Atlantic Large Whale Take Reduction Plan.