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Bat Ray

Bat Ray. Myliobatis californica. By Bridger Tillotson. Topics of Discussion:. Ecosystem/Role in Ecosystem Feeding Behavior Reproduction Human Impact. Ecosystem. Bat rays are euryhaline ; able to tolerate and live in environments with varying salinity levels.

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Bat Ray

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  1. Bat Ray Myliobatiscalifornica By Bridger Tillotson

  2. Topics of Discussion: • Ecosystem/Role in Ecosystem • Feeding Behavior • Reproduction • Human Impact

  3. Ecosystem • Bat rays are euryhaline; able to tolerate and live in environments with varying salinity levels. • Live at depths ranging from 1 to 46 meters either solitarily or in large schools with members of their own species or other species of eagle rays. • Bat rays can be found in muddy and sandy bottom bays, rocky bottom shorelines, kelp beds, estuaries and close to coral reefs. • Distribution of the species is limited to the eastern Pacific Ocean from Oregon to the Gulf of California and also near the Galápagos Islands.

  4. World Distribution

  5. Role in Ecosystem • Bat rays feed on many buried organisms; including mollusks, crustaceans, polychaetes and small bony fish. • Clams are the dominant prey item of the species. • Bat rays may help smaller fish to feed on buried organisms by uncovering them. • Preyed upon by white sharks, seven gill sharks and killer whales. Young, immature bat rays are consumed by sea lions.

  6. Bat Ray Feeding On Squid

  7. Feeding Behavior • Bat rays use their snout to dig up covered prey. • The species also captures food by waving its pectoral fins rapidly up and down to expose their prey, creating suction in the sand and digging trenches up to 20 cm deep and 4 m long.

  8. Feeding Behavior • Dentition of the species consists of a single elongated medial file and three lateral files of teeth on either side. The lower tooth plate is flat while the upper plate is convex in shape. The teeth are hexagonal, arranged in non-termino-lateral positions. These plates are used for crushing and grinding prey.

  9. Bat Ray Jaws

  10. Reproduction • Bat rays mate annually in the spring or summer. • After a male bat ray finds a suitable mate, they swim close behind the female with his back touching her underside. • The male may make repeated attempts at inserting a clasper into the female’s cloaca until successful. • During copulation, the pair swims together, moving their pectoral fins in unison. • Females may be pursued by more than one male, resulting in fights among the males. • Female bat rays form large mating aggregations, blocking other females that are immature or that have already mated. 

  11. Bat Rays Mating

  12. Reproduction • Ovoviviparous; eggs are fertilized internally and litters of up to 12 pups are born live following a gestation period of 9 to 12 months. • At birth, the pups are 30 to 36 cm wide and each weigh about 1 kg. • Pups are born tail-first with their pectoral fins rolled over the body. The spines of the pup are pliable and encased in tough sheaths, preventing injury to the female during birth. The spines harden and the natal sheath is discarded soon after birth.

  13. Human Impact • Bat rays are not currently threatened or endangered. The species is listed as "Least Concern" with the World Conservation Union (IUCN). • The species is non-aggressive and poses little threat to humans. However, bat rays possess 1 to 3 venomous spines located at the base of the tail. • Bat rays are not fished commercially in the United States, but are fished commercially in Mexico for food. The species is also targeted for sport fishing. • For many years, commercial oyster growers trapped bat rays because they thought bat rays ate large numbers of oysters. But recently researchers have discovered that bay rays rarely eat oysters, and that crabs were responsible for destroying the oyster beds. The oyster growers were actually causing the destruction of their own oyster beds by trapping bat rays, which prey on crabs.

  14. Human Impact • Bat rays are often caught in trawling and gill nets as unwanted by-catch. • Bat rays can readily adapt to captivity and are commonly displayed at public aquarium facilities; including SeaWorld, Aquarium of the Pacific and Monterey Bay Aquarium.

  15. Review Topics Discussed: • Ecosystem/Role in Ecosystem • Feeding Behavior • Reproduction • Human Impact

  16. Main Research Sources • Florida Museum of Natural History http://www.flmnh.ufl.edu/ • Aquarium of the Pacific http://www.aquariumofpacific.org/ • Monterey Bay Aquarium http://www.montereybayaquarium.org/

  17. Scientific Article • Food habits, occurrence, and population structure of the bat ray, Myliobatiscalifornica, in Humboldt Bay, California By Ann E. Gray, Timothy J. Mulligan & Robert W. Hannah

  18. Bridger’s Bat ray Presentation!

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