Baleen in mysticete cetaceans

Baleen plates are keratinous structures located in the upper jaw of baleen whales, known as mysticetes. They allow these animals to filter immense volumes of water in order to extract prey such as krill, copepods or small fish.

Origin and structure

Each baleen plate is a flexible blade of keratin embedded in the upper jaw. Its inner surface frays into fringes, which maximises filtering efficiency.

• Number of plates: between 200 and 400 per half-jaw
• Maximum length: up to 4 metres in the blue whale
• Material: alpha keratin, as in nails or feathers

Filtering mechanisms

Baleen allows mysticetes to adopt two main feeding strategies:

Filtering by lunge feeding

Used by rorquals, it consists of taking in a large volume of water and then pushing it back out through the baleen, which retains the prey.

Filtering by skimming

In the right whale, the mouth stays open continuously while the animal swims through plankton swarms.

Variation between species

Growth and wear

Baleen wears down continuously but is renewed from its base. This growth maintains a constant filtering efficiency despite the abrasion caused by water and food particles.

Scientific value

Baleen serves as a biological archive. By analysing its layered composition, scientists can reconstruct an individual’s feeding, migrations and hormone levels over several years.

Baleen is not only a tool for survival: it is also a record of an individual’s biological history.

Further features

• Some baleen plates are pigmented black or white depending on the species.
• Historically, baleen was used to make corsets and umbrellas (known as “whalebone” in the textile trade).