Baleen whales are marine mammals distinguished by their unique feeding method. Instead of teeth, they filter vast quantities of water through specialized plates in their mouths to capture prey. This adaptation allows them to thrive on small organisms, playing a significant role in marine food webs across global oceans.
Understanding Baleen Whales
Baleen whales possess baleen plates, made of keratin, the same protein found in human fingernails. These plates hang in rows from the upper jaw, resembling a giant comb. The inner edge of each plate is frayed, forming a dense mat that acts as a sieve to trap food particles.
Different species employ various feeding strategies. Gulp feeders, such as rorquals, take in enormous volumes of water and prey, then use their tongues to push the water out through the baleen, trapping the food inside. Skim feeders, like right whales, swim with their mouths open through dense patches of prey, continuously filtering water. Some species, like the gray whale, also engage in bottom feeding, stirring up sediments to filter out benthic invertebrates.
Baleen whales are among the largest animals on Earth, with some species reaching lengths exceeding 100 feet. Most species undertake extensive seasonal migrations between colder feeding grounds and warmer breeding grounds. Their diet primarily consists of small schooling organisms, including krill, copepods, and small fish, which they consume in massive quantities to sustain their large body sizes.
Classification of Baleen Whales
Baleen whales are categorized into four families. The largest is Balaenopteridae, commonly known as rorquals, recognized by their streamlined bodies and numerous throat pleats that expand during feeding. Examples include the blue whale and the humpback whale.
The Balaenidae family comprises the right whales, distinguished by their robust bodies, lack of dorsal fins, and long, arched mouths that house exceptionally long baleen plates. These whales are known for their slow swimming speeds and unique callosities, rough patches of skin on their heads. The North Atlantic right whale and the bowhead whale are members of this group.
The Eschrichtiidae family contains only one living species, the gray whale, notable for its mottled gray skin and a series of knuckles or bumps instead of a dorsal fin. Gray whales are unique among baleen whales for their habit of feeding on the ocean floor, sifting invertebrates from sediments.
The Neobalaenidae family includes one species, the pygmy right whale, the smallest of all baleen whales. This species shares characteristics with both right whales and rorquals but is distinct enough to warrant its own family. Pygmy right whales are little studied due to their elusive nature and often offshore habitats.
Distinctive Baleen Whale Species
Among baleen whales, several species stand out for their unique attributes and behaviors. The blue whale, Balaenoptera musculus, is the largest animal known to have ever lived, reaching lengths of up to 98 feet and weighing over 190 tons. Its immense size allows it to consume up to 8,000 pounds of krill per day, primarily through gulp feeding.
Humpback whales, Megaptera novaeangliae, are known for their complex vocalizations, often called songs, which can last for many minutes and are thought to play a role in mating. These whales are also known for their acrobatic displays, including breaching and pec slapping, where they leap out of the water or slap their long pectoral fins on the surface. They utilize a unique feeding technique called bubble-net feeding, where groups of whales work together to blow bubbles around prey, creating a “net” to concentrate food.
The gray whale, Eschrichtius robustus, undertakes one of the longest migrations of any mammal, traveling up to 12,000 miles round trip annually between its Arctic feeding grounds and warmer breeding lagoons in Baja California, Mexico. Their distinctive mottled gray skin, often covered in barnacles and whale lice, results from their bottom-feeding habits, where they actively churn up sediments to filter out small crustaceans and worms. This specialized feeding strategy sets them apart from other baleen whales.
Fin whales, Balaenoptera physalus, are the second-largest whale species, reaching lengths of up to 85 feet. They are often called the “greyhounds of the sea” due to their remarkable speed, capable of reaching sustained speeds of 23 miles per hour. Their unique asymmetric coloration, with a white lower jaw on the right side and a dark lower jaw on the left, is believed to aid in their lunge feeding, potentially confusing prey as they turn on their side to engulf large schools of fish or krill.