Posted by Ken Jones
on May-28-08 8:00pm
(In reply to: Treating stings from bat rays and stingrays as ... posted by Ken Jones on May-28-08 7:52pm)
Myliobatis californicus (bat ray and bat sting ray)
2004/05/18 14:28:52.207 GMT-
By Katie Schmidt
Species: Myliobatis californicus
Bat rays are found in shallow waters and coral reefs from Oregon to the Sea of Cortez.
Biogeographic Regions: pacific ocean (native ).
Bat rays are found living close to the shores of bays, sloughs, kelp beds and coral reefs. Bat rays prefer to live in areas with sandy or muddy bottoms for it allows easier access to food. They are most commonly found in depths reaching between 3m and 12m but have occasionally been spotted as deep as 46m. (Gray, Mulligan, and Hannah, 1997; Last and Stevens, 1994)
Aquatic Biomes: reef; coastal.
Bat rays are commonly distinguished from other rays because of their distinct, protruding head and large eyes (a close look). They have a flat body with a dorsal fin at the base of the tail. The tail is whiplike and can be as long or longer than the width of the body. It is armed with a barbed stinger that is venomous. Bat rays are named for their two long pectoral fins that are shaped like the wings of a bat. The skin is smooth, dark brown or black and has no markings. Bat rays have a white underbelly. The skeleton is made of cartilage, instead of bone. Bat rays are usually born measuring 11.4 inches and can grow to reach 5.9 feet. Females are typically larger than males and have been found weighing up to 200 pounds. (Details.) (Last and Stevens, 1994; Michael, 1993)
physical features: bilateral symmetry .
Bat rays reproduce on an annual cycle, usually copulating during the spring or summer of one year and then giving birth the following spring or summer. The male chooses his mate by following close behind her and assessing her reproductive condition by smelling her chemical signals. When the male has found a suitable mate, he continues to swim close behind and moves under so that his back is touching her stomach. He rotates a clasper up and to the side of the female. After inserting it into her cloaca, they swim together with synchronous beats of the pectoral fins. Many times, males will fight over a particular female. The female may end up having more than one male clinging onto her pectoral fins at one time and will wait for one of the males to finally flip her into the correct position. Bat rays reproduce in large mating aggregations with the females clustering in one area. Females may lie on top of one another, burying females that have already mated or those that are not sexually mature yet. This allows less confusion for the males to pick a suitable mate.
The gestation period is between 8-12 months and the number of live young born depends upon the size of the mother but can be up to 10 pups at a time. The female enters a bay area to deliver in an effort to protect from larger predators in the ocean and to allow access to a more stable food source. The young pups do not require any parental care and are born with stingers ready to protect from predators. Before bat rays are actually born, the stinger is pliable and has a sheath that is sloughed. It protects the mother from the dangerous stinger during delivery but is immediately lost at the time of delivery. Bat rays reach sexual maturity around the age of 5 years, usually when they measure from wing tip to wing tip 67-68 cm. (Last and Stevens, 1994; Michael, 1993)
Bat Rays are usually solitary animals but have been seen swimming in groups of thousands. They also swim with other rays from the same family (eagle ray). Females stick together and usually live where large amounts of food are found. Bat Rays move around a lot, even during copulation, and are noted for their ability to "jump out of water" and skim along the surface for several seconds. This is often described as looking like "flying". (Gray, Mulligan, and Hannah, 1997; Last and Stevens, 1994)
Key behaviors: natatorial; motile .
Bat rays are carnivorous and feed on a variety of molluscs, crustaceans, and small fishes. They have adapted to eat whatever food is most abundant in the environment, which may include polychaete worms, abalone, oysters, snails, shrimp, crabs, and bony fish. Juveniles eat clams while adult bat rays are the only stage that eats echiuroid worms.
Bat rays use their snout to dig invertebrates from the sand, making the bat ray an important benthic predator. They also capture prey by lifting the body on the pectoral fin tip, flapping the pectoral tips quickly up and down, and then using the suction created by the flapping to pull sand out from under the body, exposing hidden prey. When bat rays feed on molluscs, they eat the entire animal, crush the shell inside of the mouth, spit out the hard shell pieces, and then eat the soft part of the mollusc body. Bat rays, depending on size, may burrow with their nose deeper into the sand or mud bottoms in an effort to eat larger prey. (Gray, Mulligan, and Hannah, 1997; Talent, 1982)
Economic Importance for Humans: Negative
Bat rays feed on oysters in large amounts and because of this, they are considered a great threat to oyster growers. As a result, oyster growers in the Humbodlt Bay area have trapped them for over 37 years. (Gray, Mulligan, and Hannah, 1997; Michael, 1993)
Economic Importance for Humans: Positive
Because bat rays are large predators that use their snouts to dig up food, they wind up creating extremely large pits up to 4m long and 20 cm deep. These large pits allow access to small organisms that may be the food of smaller fish. Small fish rely on this relationship with bat rays because a lot of them are unable to dig their own food out of the sand.
* Bat rays have been known to live up to 23 years.
* Predators of the bat ray are the California sea lion and the broadnose sevengill shark
* Bat ray fossils have been discovered in Pliocene deposits dating back 1 million years.
* The origin of the name "bat ray" was given by Gill in 1865 because of their pectoral fins which resemble bat wings.
* Bat rays have been successfully bred at Sea World.
(email response from Sea World, 2000:Talen,1982:Gray, Mulligan, and Hannah,1997)
Katie Schmidt (author), University of Michigan: June, 2000.
Tanya Dewey (editor), University of Michigan: June, 2000.
Gray, A., T. Mulligan, R. Hannah. 1997. Food habits, occurence, and population structure of the bat ray, Myliobatis Californica, in Humboldt Bay, California. Environmental Biology of Fishes, 49: 227-238.
Last, P., J. Stevens. 1994. Sharks and Rays of Australia. Australia: CSIRO.
Michael, S. 1993. Reef Sharks & Rays of the World: A guide to their identification, behavior, and ecology.. Monterey, California: Sea Challengers.
Talent, L. 1982. Food Habits of the Gray Smoothhound, Mustelus Californicus, the Brown Smoothhound, Mustelus Henlei, the Shovelnose Guitarfish, Rhinobatos Productus, and the Bat Ray, Myliobatis Californicus, in Elkhorn Slough, California. California Fish and Game, 68: 224-234.
2004/05/18 14:28:53.267 GMT-4
To cite this page: Schmidt, K. 2000. "Myliobatis californicus" (On-line), Animal Diversity Web. Accessed May 31, 2004 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Myliobatis_californicus.html.
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Treating stings from bat rays and stingrays as ... Ken Jones - May-28-08 7:52pm
Myliobatis californicus— Ken Jones - May-28-08 8:00pm