Some of the ocean’s largest animals use a feeding system called baleen to consume vast quantities of tiny prey. This structure allows certain whale species to filter small organisms from enormous volumes of water, sustaining their massive bodies. This adaptation is a defining characteristic of an entire suborder of whales, setting them apart from their toothed relatives.
Composition and Structure of Baleen
Contrary to what its historical name “whalebone” might suggest, baleen is not made of bone. It is composed of keratin, the same fibrous structural protein that makes up human hair and fingernails. These keratin-based structures manifest as a series of long, flexible plates that are suspended in rows from the whale’s upper jaw. Depending on the whale species, there can be between 150 and 400 of these plates on each side of the mouth.
The structure of each individual plate is specialized for filter-feeding. While the outer edge is smooth, the inner edge, which faces the whale’s tongue, is frayed into fine, hair-like bristles. These bristles from adjacent plates overlap and intertwine, forming a dense, comb-like mat inside the whale’s mouth. This intricate network of bristles is what functions as the sieve.
The plates themselves vary significantly in size among species, from about one foot in minke whales to over 13 feet in bowhead whales. This material is both strong and flexible, and it grows continuously throughout the whale’s life to counteract wear from its constant use. The composition is a composite of keratin tubes and a calcified matrix, which gives the baleen the necessary stiffness to withstand the pressures of feeding.
The Filter-Feeding Mechanism
A baleen whale feeds by first taking an immense gulp of ocean water, which is rich with small prey like krill, copepods, and tiny fish. Once its mouth is full, the whale uses its large tongue to press upwards against the palate, forcing the water out of its mouth.
The water is expelled through the gaps between the baleen plates, but the food is trapped by the intricate mesh of keratinous bristles on the inside. The whale then scrapes the captured food off the baleen with its tongue and swallows it.
Whales employ different techniques to utilize their baleen. Some, like humpback and blue whales, are “lunge-feeders.” They actively lunge into dense swarms of krill or fish, engulfing both prey and water, and their pleated throats expand to accommodate the volume. Others, such as right whales, are “skim-feeders.” They swim slowly with their mouths open, continuously filtering plankton from the water’s surface.
Whales With Baleen
All whales that possess baleen belong to the scientific suborder Mysticeti. This group includes some of the most well-known whale species, such as the blue whale, humpback whale, fin whale, gray whale, and right whale. There are currently 16 recognized species of baleen whales.
This suborder stands in contrast to the other major group of cetaceans, the Odontoceti, or toothed whales. This group includes all dolphins and porpoises, as well as species like orcas, sperm whales, and belugas. Instead of baleen, odontocetes have teeth and typically hunt larger, individual prey like fish and squid. The two groups also differ in other ways; mysticetes have two blowholes, while odontocetes have only one.
Historical Use in Human Products
Before the widespread availability of plastics and other modern polymers, the unique properties of baleen made it a highly sought-after material. Its combination of strength and flexibility was unmatched by most other natural materials. This valuable commodity was a primary driver of the global whaling industry for centuries.
Common uses for baleen included:
- Stays in women’s corsets
- Umbrella ribs
- Buggy whips
- Collar stiffeners
- Fishing rods
- Hoops for crinoline skirts
The demand for baleen, alongside the desire for whale oil, led to extensive hunting that severely depleted the populations of many baleen whale species.