What material are baleen plates made of?

Baleen plates are made of keratin, the tough protein also found in human hair, fingernails, and the outer layer of skin.

These plates hang from the whale’s upper jaw in two rows. Instead of chewing food, a baleen whale takes in a large mouthful of seawater containing krill, copepods, small fish, or other prey. The whale then pushes the water back out with its tongue. Fine keratin fibers along the inner edge of the plates trap the food while the water escapes.

Baleen is not bone, cartilage, or tooth enamel. The old term “whalebone” is therefore misleading: baleen is a flexible, keratin-based filter rather than a skeletal structure. Its stiffness varies among species, and some baleen is partly mineralized with calcium compounds, which reinforces the plates without changing their basic keratin composition.

Before modern plastics, people used baleen for corset stays, umbrella ribs, buggy whips, and other objects needing both flexibility and strength. Today, the material is best understood as a remarkable natural feeding system rather than a form of bone.