Bat Stars have short, triangular arms, usually five in number but sometimes four to nine. Their color is extremely variable, but most are red or deep orange. Bat Stars function as marine scavengers and tend to congregate in large numbers where other animals are dead or dying. They feed by extending their stomachs over a plant or animal, whether dead or alive, and slowly digesting it.
They are territorial and will often engage each other in bouts of gentle arm-wrestling to protect a meal. When they cannot scavenge, Bat Stars will extend their stomachs into the seawater to trap suspended organic particles.
Bat Stars spawn mainly in early summer but they have no clear reproductive cycle. They release orange eggs and white sperm from pores between the arms on the upper surface of the body.
Bat Stars are common from Sitka, Alaska to Baja California. They live among rocks overgrown with surfgrass in the low intertidal zone and on seafloors covered with rocks, shells, gravel, hard sand or algae up to 951 feet (290 m) deep.