Whale Trust Maui Blog

Each year, tens of thousands of whales travel thousands of miles from their summer feeding grounds to winter breeding grounds. Hawaii, and most abundantly the shallow waters between Molokai, Lanai, Kahoolawe and Maui, is the largest breeding ground for North Pacific whales, most of whom are coming from the northwest coast of North America.

Although researchers still don’t understand why whales migrate to these winter grounds, it appears to be more for physical than biological characteristics. Most breeding grounds are warmer, shallower, and more protected than summer feeding areas, which may offer increased protection for mothers and their newborn calves. The dense congregation of whales that assemble in these winter grounds also brings together males and females, who may feed in different areas during the summer.

The sea conditions in Hawaii, including calm lees protected from trade winds, clear, warm water, and easy access to humpback whales make the Hawaiian Islands one of the best natural laboratories in the world to study whales.

What is a Breeding Ground?

Humpback whales have a specific reproductive cycle with the same components as all mammals: mating, gestation, birth and nurturing young. The typical reproductive cycle of a mature female humpback is: mating in winter, a year’s gestation, birth of one baby during the following (second) winter, a year’s care of the baby prior to weaning, then separation in the third winter followed by mating again. As most of the mating, birthing and nursing takes place during the winter months, the area they spend the winter becomes the “breeding ground”.

It is important to note, however, the “breeding ground” does not necessarily imply a rigid boundary for these behaviors. Reproductive activities begin, and some births occur, before whales reach Hawaii. In fact, some behaviors such as singing (a behavior not necessarily related to breeding per se but which is prevalent in breeding grounds and generally absent from feeding grounds) begin as early as late fall before the whales leave their summer feeding grounds. Reproductive activities also continue to some extent on the northern migration back to feeding grounds.

Whales, dolphins and porpoises are all grouped together under one taxonomic order called Cetacea.

Diversity is perhaps the most striking hallmark of the cetaceans, with over eighty different species of whales, dolphins, and porpoises recognized today. Cetaceans range in size from the small four-five foot porpoises and dolphins to the largest animal ever to live on earth, the 80-110 foot blue whale. Life spans also differ; humpbacks are believed to live at least 50-60 years while the bowhead whale is known to live at least as long as 120 years, and possibly as long as 200 years!

Cetaceans inhabit most of the world’s oceans, some traveling thousands of miles each year between high latitude feeding areas and lower latitude breeding and calving areas, while others live year around in fairly restricted areas. Some cetaceans even inhabit the world’s largest rivers.

Mysticetes vs Odontocetes

Based on the presence or absence of teeth, cetaceans are generally divided into two groups or suborders: the Mysticetes (baleen whales); and the Odontocetes (toothed whales).

Mysticetes

Baleen whales are also called mysticetes, which means “mustached whale”. Scientists currently recognize thirteen species of mysticetes, grouped into four living families. Humpback whales are one of six species belonging to the Balaenopteridae family or rorqual family. All rorquals have ventral pleats on the underside of their throat that allows them to expand their throat greatly while feeding. Other families of mysticetes include the Balaenidae (right and bowhead whales), the Eschrichtiidae (gray whale), and the Neobalaenidae (pygmy right whales).

Characteristics of Baleen Whales

Baleen

The term “baleen” refers to the plates found in the mouths of these types of whales that are used to filter out prey from the water. These plates are made out of a flexible protein called keratin and suspend from the palate arranged in rows. Different species have varying amounts of these plates. Fin whales, for example, have between 800-900 plates whereas humpbacks have only about 300. The plates can also vary in size, texture, and color between species.



Different families of baleen whales feed on different types of prey and rely on different feeding techniques to capture this prey. Humpback whales feed primarily on small schooling fishes such as capelin or herring, or shrimp-like crustaceans called krill (pictured below left), while gray whales are known as benthic or bottom feeders and feed primarily on small amphipods (see grey whale picture, top left) or mysids. Right and bowhead whales are primarily skim feeders, swimming through swarms of plankton with their mouths open.

Two Blowholes

As marine mammals, all whales, dolphins and porpoises breathe air through an external blowhole, located on the top of the whale’s head. All mysticetes have two blowholes, whereas odontocetes have only one blowhole.

Ventral Pleats

Humpback whales, like blue whales and other rorquals, have a number of expandable pleats on the underside of the throat. These pleats allow whales to expand their mouth to an enormous size when feeding so they can consume massive amounts of small prey at one time, or allow whales to appear larger when competing for access to a female on the breeding grounds (pictured right.)

Characteristics of Toothed Whales

Odontocetes

Toothed whales are also called odontocetes (coming from the Greek word ‘odont’ meaning tooth). There are at least 71 species of toothed whales, including all of the dolphins and porpoises and some species of whales, including the medium-sized killer and pilot whales, as well as the larger beaked whales and the largest odontocete, the 60-foot sperm whale. Some toothed whales, however, like the narwhal (Monodon monoceros), have no functional teeth at all. Male narwhals have a single tooth that erupts from the gums and can grow up to ten feet in length, called the narwhal tusk.

Prey

Types of prey vary substantially between different species of toothed whales, ranging from various types of schooling fish and squid to larger predatory fish like mahi-mahi (dolphin fish). Some species like the killer whale even prey on other marine mammals, including some of the largest baleen whales.

Families

Ten living families of odontocetes are recognized including Phocoenidae (porpoises), Delphinidae (true dolphins) Monodontidae (belugas, narwhals), Kogiidae (Pygmy and dwarf sperm whales), Physteridae (sperm whale), Ziphidae (beaked whales), Platanistidae (Indian River Dolphin), Iniidae (Amazon River dolphin), Pontoporiidae (Fransiscana) and Lipotidae (Yangtze river dolphin).

Echolocation

Unlike the mysticetes, odontocetes have only one external blowhole and possess echolocation capabilities. Echolocation is a way that toothed whales can assess their surrounding environment. By emitting a series of sounds and then listening to the returning echoes, toothed whales are essentially able to see with sound. As the produced sounds bounce off different objects in the environment, the returning echo provides valuable information on the object such as its size, shape and distance away. Echolocation is a vital way that toothed whales locate prey and detect predators.

From Calf to Sexually Mature Whale

Humpback whales take approximately five to fourteen years to reach sexual maturity.
[Read more…] about When Do Whales Reach Sexual Maturity?