The bat ray (Myliobatis californica) is an eagle ray found in muddy or sandy sloughs, estuaries and bays, kelp beds and rocky-bottomed shoreline in the eastern Pacific Ocean, between the Oregon coast and the Gulf of California. It is also found in the area around the GalÃ¡pagos Islands. The largest specimens can grow to a wingspan of 1.8Â m (5Â ft 11Â in) and a mass of 91Â kg (201Â lb). They more typically range from 9.07â"13.61Â kg (20.0â"30.0Â lb). Bat rays are euryhaline, i.e. they are able to live in environments with a wide range of salinities.
Bat rays feed on mollusks, crustaceans and small fish on the seabed, using their winglike pectoral fins to move sand and expose prey animals. They may also dig trenches up to 20Â cm deep to expose buried prey, such as clams. Bat ray teeth are flat and pavementlike, forming tightly-packed rows that are used for crushing and grinding preyâ"the crushed shells are ejected and the flesh consumed. As with all elasmobranchs, these teeth fall out and are replaced continuously.
Relation to humans
While the bat ray, like other stingrays, has a venomous spine in its tail (near the base), it is not considered dangerous and uses the spine only when attacked or frightened.
Currently, the bat ray is fished commercially in Mexico but not the United States. However, it is sometimes fished for sport for its fighting characteristics. Prehistorically, native tribes on the California coast (probably Ohlone), especially in the San Francisco Bay area, fished bat rays in large numbers, presumably for food.
Commercial growers have long believed bat rays (which inhabit the same estuarine areas favored for the industry) prey on oysters, and trapped them in large numbers. In fact, crabs (which are prey of bat rays) are principally responsible for oyster loss. Bat rays are not considered endangered or threatened.
Bat Rays are popular in marine parks, and visitors are often allowed to touch or stroke the ray, usually on the wing.
Bat ray reproduction is ovoviviparous. They mate annually, in the spring or summer, and have a gestation period of nine to twelve months. Litter sizes range from two to ten â" pups emerge with their pectoral fins wrapped around the body, and the venomous spine is flexible and covered in a sheath which sloughs off within hours of birth. Bat rays live up to 23 years.
Bat rays copulate while swimming with synchronized wingbeatsâ"the male under the female. The male inserts a clasper into the female's cloaca, channeling semen into the orifice to fertilize her eggs.