Humpback Whales

Humpback Whale (Megaptera novaeangliae)

Hawaiian Name: Koholā

Indigenous (migratory).

Status: Endangered Species.

[Illustration: Humpback mother with calf]

It’s not often you see a animal as big as a large school bus fly up into the air and then come crashing down on the water in a chaos of sound and water. In the Hawaiian Islands, however, where humpback whales are known for their spectacular breaches, this is not an unusual sight.

Adult humpback whales may be 45 feet (14 m) long and weigh more than 40 tons (36 mtons). Newborn humpbacks are very light colored (almost white), but their color begins darkening within the first two weeks.

Humpback calves are about 12 feet (3.7 m) long at birth, weigh about 1.5 tons (1.4 mtons), and may feed on more than 100 gallons (379 liters) of their mother’s milk each day.

The humpback whales around the Hawaiian Islands are part of the North Pacific humpback population, which spends the summers near Alaskan waters feeding.

Less than two-thirds of the North Pacific humpbacks migrate to the tropical seas around the Hawaiian Islands each winter to mate and give birth. The remainder migrate to other areas near Mexico, California, Japan, and the Marianas Islands near Taiwan.

 

Anatomy

Humpbacks have two blowholes, called nares, on the top of their head. On the front of the humpback’s head (on the upper and lower jaws) are many sensory nodules, which are golf-ball sized bumps also referred to as tubercles. Each tubercle contains a hair called a vibrissa, which helps the whale sense vibration and temperature.

Twelve to 30 ventral pleats, or throat grooves, span two-thirds of the length of the humpback whale’s underside. These long, furrowed ventral pleats contain the extra skin that allows the whale’s huge mouth to expand open during feeding.

Baleen

The humpback is a baleen whale. Instead of having jaws with teeth to grab prey, they filter their food from the water using the plates of baleen that hang from their upper jaw. The baleen is comprised of chitin, which is similar in hardness to human fingernails.

The humpback’s hair-like strips of baleen fuse together to form larger plates, about 335 of them, each about 6 inches (15 cm) wide and 2.5 feet (.8 m) long with about 35 bristles.

The ends of the baleen strips are frayed, and intertwine to form a food-filtering system. Before plastic was invented, baleen was used for women’s corsets, hoop skirts, umbrellas, and a variety of other products that required strong, flexible material.

Feeding

North Pacific humpbacks feed in northern waters during the winter, feasting mostly on the tiny shrimp-like creatures known as krill, as well as small fish such as herring.

The feeding humpback fills its mouth with more than 1,000 gallons (378,500 liters) of water, and then strains the water out through the baleen, which keeps the food inside. The whale then uses its 2-ton (1.8-mton) tongue to help swallow the food in gulps down its relatively small throat, which only opens to about 10 inches (25 cm) in diameter.

In their summer feeding waters off the coast of Alaska, humpback whales sometimes use a technique known as bubblenet feeding. While spiraling inward around a school of fish such as herring, the humpback whale releases air, which confuses the fish and then traps them within the curtain of bubbles.

The whale then swims below the school, opens its huge mouth, and scoops up a nice meal by coming right up through the chaotic frenzy of fish. With fish jumping at the surface and birds diving down to get the fish, whales may sometimes accidentally swallow a bird or two.

[Illustration: Bubblenet feeding]

Breaching

In the last two decades, whale-watching has become a worldwide recreational industry, and seeing a whale breach is the highlight of any whale-watching trip.

During a typical breach, the humpback whale leaps upward (usually about 2/3 of the whale’s body comes out of the water), spins around 180 degrees in mid air, and then lands on its back with a huge splash. Breaching humpback whales are a common sight in Hawaiian waters during winter.

[Illustration: Breaching Whale]

Researchers theorize that humpback whales may breach for a variety of reasons. Humpbacks have a special eye lens adapted to seeing in air, and may breach to look around above water. They may also breach to knock barnacles off their body, and male humpbacks may breach to impress females during the breeding season.

Breaching may also be a form of communication. Often one whale will breach, and then another whale will suddenly breach some distance away, possibly in response to the sound of the first whale hitting the water.

Humpback calves are sometimes seen breaching over and over again, and this may simply be the baby imitating the behavior if its mother. Researchers also have not been able to rule out the possibility that breaching may be a form of play for the whales. In other words, whales may complete these amazing acrobatic pirouettes simply because it’s fun!

Other Humpback Behaviors

Aside from breaching, there are numerous other humpback behaviors commonly seen by whale watchers. These typical behaviors include:

Ø Pec Slap—Slapping a pectoral fin down onto the surface.

Ø Fluking—Lifting the tail fluke up out of the water in preparation for diving down.

Ø Tail Slap—Slapping just the tail fluke down onto the surface.

Ø Peduncle Slap—Lifting the whole back region of the body out of the water and then slapping it down onto the surface.

Ø Head Slap—Slapping the lower jaw onto the water’s surface.

Ø Spy Hop—Rising up from the water head first, as if to look around.

Ø Spouting—Sending up sprays of mist (from the blowholes) while breathing at the water’s surface.

Ø Round Out—Also called peduncle arch. Arching its back above the surface and then raising its tail fluke and diving below. This behavior led to the name “humpback.”

Ø Singing—Emitting patterned sounds (described below).

Humpback Songs

Humpbacks don’t have vocal cords, yet they sing beautiful, complex songs. Generally, only the males sing, and they only sing in the winter mating waters (such as the waters around the Hawaiian Islands). Male humpback singing is thought to be related to the courtship of females, and may be a sort of love song to win the favor of the females.

Scientists analyzing humpback singing have found that the songs are composed of a series of repeated phrases and themes. One song may last about 20 minutes, and may be repeated over and over again, often for many hours in a row.

Though humpbacks have no functional vocal cords, they nevertheless have a broad tonal range, producing the highest and lowest frequencies humans can hear, as well as tones beyond the range of human hearing.

All of the humpback whales around the Hawaiian Islands are basically singing the same song, perhaps imitating the mating song of the most successful whale.

Each week the song changes just a little bit, and all the humpbacks make this same change. In this manner, the group’s song changes gradually over time so that, by the end of the mating season, the song is very different than it was at the beginning of the season.

When the whales return to their feeding waters in Alaska they stop singing until the next year when they come back to the Hawaiian Islands. When the whales return to the tropical waters of the Hawaiian Islands, they take up singing the same song just as it was when they left Hawaiian waters the year before.

The humpback whale is the only animal known to have such an evolving song, and to have an actual rhythm in its complex songs.

Population

Before commercial whaling there were approximately about 200,000 humpbacks in the world’s oceans. Commercial hunting of humpbacks throughout the 1900s decimated the species.

From 1960 to 1965, more than 5,000 North Pacific humpbacks were killed. When the total ban on hunting humpbacks was enacted by the International Whaling Commission in 1966, there were likely fewer than 1,000 humpbacks left.

Today the population of North Pacific humpback whales is estimated at less than 9,000 (estimates range from 6,000 to more than 8,000), with about 3,700 to 5,000 of the whales migrating to the Hawaiian Islands each year to mate and give birth. This number has been growing about 7% per year for the last decade.

Added protection was given to the humpback species when a large area around the Hawaiian Islands was designated as the Hawaiian Islands Humpback Whale National Marine Sanctuary on November 4, 1992. Governor Benjamin Cayetano approved the Sanctuary in State of Hawai‘i waters on June 5, 1997.

Numerous humpback studies have been undertaken in recent years. A 2002 study of humpbacks utilized satellite transmitters on humpbacks off Brazil’s Atlantic coast, tracking the whales to the Antarctic more than 2,000 miles (3,219 km) away. The research’s conclusions about migration paths will be used as part of the case for establishing a whale sanctuary in the South Atlantic.

In 2003 at least 100 scientists from North America, Central America, Russia and other countries began developing a new study known as Structure of Populations, Levels of Abundance and Status of Humpbacks (SPLASH).

The study’s goals include obtaining a more accurate humpback whale population estimate as well as a better analysis of humpback genetics and evolution using biopsy sampling. Also to be studied is humpback diet, mating, mortality, migratory routes, and regional populations.

Another 2003 study analyzing humpback whale DNA concluded that historical North Atlantic humpback whale populations were much larger than previously thought, as were populations of fin and minke whales. Conducted by Harvard’s Stephen R. Palumbi and Stanford’s Joe Roman and published in July, 2003 in the journal Science, the study estimated the pre-hunting humpback population at 240,000, up from a previous estimate of as little as 20,000.

The new DNA study also raised the estimate of the pre-hunting fin whale population to 360,000, up from previous estimates ranging from 30,000 to 50,000. The pre-hunting minke whale population estimate was raised to 265,000, up from about 100,000.

Continuing research will attempt to explain the wide disparity between the new estimates and the previous estimates, with broad implications for when a species is considered endangered, which is based on considering the current population in comparison to historical populations.

Migration

After spending the summer months northern waters, the first humpback whales begin arriving near the Hawaiian Islands around November. These first whales are usually the whales that gave birth the previous year along with their yearling calves, which will be weaned during their winter stay in Hawaiian waters.

Sometimes males and yearling calves arrive together. The last humpback whales to arrive in Hawaiian waters are the pregnant mothers who stay in northern waters as long as possible to be well fed for the rigors of giving birth and nursing, not to mention the long migration to the Hawaiian Islands.

The humpback population around the Hawaiian Islands peaks around January, and then in spring the whales begin to leave again. The last whales to leave Hawaiian waters are the mothers with their newborn calves, who typically leave around May to begin the journey north.

A mother humpback may have lost up to 25% of her body weight from the time she leaves Alaskan waters to the time she returns.

In 1995, Oregon State University researcher Bruce Mate used satellite-monitored radio transmitters (shot into the whales from a crossbow) to monitor humpback whales, recording distances of up to 90 miles (145 km) per day traveled by tagged whales. Three tagged whales began their annual migration from Kaua‘i’s Nāpali coast, swimming separate but basically parallel routes toward the Gulf of Alaska.

The direction of two of these whales, an adult and a sub-adult, was almost directly magnetic north, while the third tagged whale, which was accompanied by a calf, traveled in a direction just east of magnetic north.

Interisland travel was also tracked among several whales. One tagged whale swam near five islands in a ten day period, and also spent time at Penguin Bank, a coral-covered shoal west of Moloka‘i that is often frequented by humpbacks and various other cetaceans.

To report a stranded or entangled whale, or a whale being harassed by humans, call the Marine Mammal Hotline at 888-256-9840.

Other Cetaceans Around the Hawaiian Islands

Of the 78 species of cetaceans (whales, dolphins, and porpoises) worldwide, 22 species are known to inhabit Hawaiian waters, and thus may be considered native to the Hawaiian Islands. These native cetacean species include 17 Odontocetes (e.g., toothed species, such as dolphins), and five Mysticetes (e.g., baleen whales, such as the humpback).

One whale with a prominent role in ancient Hawaiian culture was the palaoa (Physeter macrocephalus, sperm whale), which is a toothed species (Odontocete), unlike the humpback whale, which is a baleen whale (Mysticete). The teeth of the palaoa were used by ancient Hawaiians to make the prized lei niho palaoa (whale tooth pendant). (See Lei Niho Palaoa in Lei Flowers section, Chapter 3.)

In August of 2001 a 10-foot (3-m) long, 1,200-pound (544-kg) baby sperm whale (Physeter macrocephalus) beached itself on the island of Hawai‘i’s Kona shoreline. Though public volunteers and officials attempted to save the whale, placing it in a tank and feeding it, the whale died.

Another whale historically seen in the Hawaiian Islands is the right whale (Eubalaena glacialis). In the 1800s, commercial whalers killed 97% of all right whales. Today there are about 200 right whales left in the North Pacific Ocean.

Other whales also seen around the Hawaiian Islands include short-finned pilot whales (Globicephala macrorhynchus); killer whales (Ornicus orca); false killer whales (Pseudorca crassidens), pygmy killer whales (Feresa attenuata), melon-headed whales (Peponocephala electra); pygmy sperm whales (Kogia breviceps); dwarf sperm whales (Kogia simus); minke whales (Balaenoptera acutorostrata); northern bottlenose whales (Hyperoodon ampullatus) and two species of beaked whales: the Cuvier’s beaked whale (Ziphius cavirostris) and the Blainville’s beaked whale (Mesoplodon densirostris).

The largest of all whales is the blue whale (Balaenoptera musculus), not known to be native to the Hawaiian Islands, though blue whales do inhabit the Pacific Ocean and so they may sometimes come near the Hawaiian Islands.

The largest blue whale on record measured 190 feet (58 m), which is bigger than the biggest known dinosaur. The largest humpback whale ever documented was 88 feet (26.8 m) long.