Bat rays (Myliobatus californica) are found in sandy and muddy bays and sloughs, as well as rocky areas. They swim gracefully by flapping their batlike wings, or pectoral fins. The flapping motion, when done in the sand, exposes buried invertebrates that they feed on. They also use their snout to dig for prey and have fused teeth that can crush strong shells, which they then spit out, eating the soft, fleshy parts. Bat rays can be found feeding in the intertidal zone during high tide.
Bat rays mate during the summer months, followed by a gestation period of nine to 12 months. They give birth to two to ten live young. Pups emerge tail first and their stinging spines are covered with a sheath that sloughs off to protect the mother during birth. They can grow to a wingspan of six feet, but this size is uncommon.
Although they have one to three venomous barbed spines at the base of their tail, the docile animals only sting to defend themselves.
For many years, oyster growers trapped bat rays because they thought bat rays ate large numbers of oysters. But recently researchers have discovered that bat rays rarely eat oysters, and that crabs were destroying the oyster beds. The oyster growers were actually causing the destruction of their own oyster beds by trapping bat rays, which eat crabs.
Baylands Ecosystem Species and Community Profiles: Life histories and environmental requirements of key plants, fish and wildlife. Prepared by the San Francisco Bay Area Wetlands Ecosystem Goals Project.