Atlantic Bottlenose Dolphins (Tursiops truncatus)
About Whales, Dolphins & Porpoises
Cetaceans
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.
Amazon River Dolphin (Boutu), (Inia geoffrensis)
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.
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), which are explored in greater detail below.
Characteristics of Baleen Whales (Mysticetes)
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).
Photo above right: Gray whale (Eschrictius robustus) feeding on shrimp-like organisms called amphipods on the ocean floor.
Baleen
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.
Photo, top right: A right whale in the process of skim-feeding on plankton.
Photo, bottom right: Baleen Whales feed on a variety of small, shrimp-like ocean-dwelling organisms of zooplankton called 'krill'.
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.
Photo, right: The two blowholes are shown open as this humpback whale (Megaptera novaeangliae) surfaces to breathe.
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.)
Photo, top right : The ventral pleats of a humpback whale (M. novaeangliae) are shown extended as the whale closes its mouth after a feeding episode.
Photo, bottom right : The ventral pleats of a humpback whale (M. novaeangliae) are shown extended as a whale lunges above the surface on the Hawaiian breeding grounds.
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Characteristics of Toothed Whales (Odontocetes)
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.
Photo, top right : Killer Whale (Orcinus orca)
Photo, bottom right : Sparring Narwhal Whales
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.
Photo, right: A false killer whale (Pseudorca crassidens) attacks a mahi-mahi (Coryphaena hippurus) in the waters off Hawaii.
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).
Photo, right: Beluga Whale
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.
Photo, right: Toothed whales, unlike the baleen whales, have only one blowhole as shown in this picture of a sperm whale (Physeter macrocephalus)
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General Information
Longevity
Whales are generally long-lived mammals, but longevity differs
between species and sometimes between sexes. Although the average
lifespan of a humpback whale is currently unknown, they are believed
to live at least as long as 50-60 years. Some species of whales,
however, like the bowhead whale are now known to live at least as
long as 120 years, and possibly as long as 200 years.
Photo, right: Bowhead Whale(Balaena mysticetus).
Size
The sizes of cetaceans range from the small 4-5 foot porpoises
and the critically endangered Hector’s Dolphin (Cephalorhynchus
hectori) to the blue whale (Balaenoptera musculus),
the largest mammal to ever live on earth. In general, baleen whales
tend to be larger than toothed whales, but the 60-foot male sperm
whale is larger than many Mysticetes, including the humpback whale.
Humpback whales are considered a medium-sized baleen whale, with
adults averaging 40-45 feet in length and weighing approximately
one ton per foot.
Photo, right: A humpback whale dwarfs this 24-foot boat used by Whale Trust scientists.
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