Week 2: Baleen Whales (Mysticetes) and Toothed Whales (Odontocetes)
Baleen Whales (Mysticetes)
Baleen whales are also called mysticetes, which means "mustached whale". Scientists currently recognize fifteen species of mysticetes, grouped into four living families. Humpback whales are one of six species belonging to the Balaenopteridae family or rorqual family. All rorqual whales 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
The presence of baleen, or the absence of teeth is the primary characteristic defining the mysticetes or baleen whales. Instead of teeth, the mouth contains hundreds of plates of baleen (also known as whalebone) that are made of keratin, or the same substance that human hair and fingernails are derived from.The plates hang from both sides of the upper jaw of the whale’s mouth and are hardened on the outside but frayed on the inside like a broom.
These baleen plates act like a filtration system helping large whales to consume vast quantities of small prey at one time. When a humpback whale is feeding, it opens its mouth taking in huge volumes of water and prey at one time. It then uses its tongue to press the water through the baleen but unlike the water, the prey become trapped in the hair on the inside of the baleen. After the water is expelled, the whale uses its tongue to help sweep the inside of its mouth and swallow the prey (see below for more information on prey).
Baleen Whales have Two Blowholes; Toothed Whales have One Blowhole
As marine mammals, all whales, dolphins and porpoises breathe air through an external blowhole, located on the top of the whale’s head. All baleen whales have two blowholes, whereas toothed whales (like dolphins) have only one blowhole.
Prey and Feeding Strategies for Baleen Whales
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, while gray whales are known as benthic or bottom feeders and feed primarily on small amphipods or mysids. Right and bowhead whales are primarily skim feeders, swimming through swarms of plankton with their mouths open.
The Toothed Whales or 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.
Families of Toothed Whales
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).
Toothed Whales Echolocate and Have One Blowhole
Unlike baleen whales, toothed whales 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.
Prey for Toothed Whales
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.
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