It’s the Halloween edition of Featured Species Friday! This week we are taking a closer look at a species that was named for its bat-like wings, the Bat Eagle Ray (Myliobatis californica). The bat eagle ray is a broad, angular shaped ray that can grow to up to 6 feet (1.8 m) across. It also has a round, protruding head that adds to its batty appearance. Like many species of ray, they have no caudal fin, but instead have a long, whip-like tail with up to 5 short stinging spines at the base. Its tail is preceded by a short dorsal fin, and some individuals have a series of ridges or bumps along their medial spine before the dorsal (Tricas et al., 1997). The bat eagle ray, or the bat ray as it is commonly referred to, is a member of the family Myliobatidae which includes other eagle rays, manta, and devil rays.
The bat ray spends its life living near the seafloor at depths typically less than 165 feet (50 m), though they have been documented at depths as great as 590 feet (180 m). The spend their days foraging in estuaries and bays for their favorite prey: crustaceans and bivalves. To crack open such hard prey, they have specialized pavement-like teeth. The central row are large, thick, flattened, hexagonal teeth, which are surrounded by three lateral rows of smaller crushing teeth (Klimley, 2013). When a bat ray bites into bivalve, the juicy, meaty parts are ingested, and the hard exoskeletons are spat back out (van Hees et al., 2015).
Take a moment and watch these adorable baby bat rays at the Monterey Bay Aquarium feed on some of their favorites. Try not to saw “aww.” I dare you!
Monterey Bay Aquarium. (Videographer). (2017 March 9). Feeding Time for the Baby Bat Rays! [Video Clip]. Retrieved from https://www.youtube.com/
Bat rays are fairly common along the western coast of North America from as far south as Baja California upwards to Oregon. These rays are constantly looking for new areas to forage, and when they find bountiful feeding grounds, they go nuts! One study found that over a 24 hour period, one bat ray moved continuously without returning to a “refuge” or a home site (Klimley, 2013). The figure below depicts the movements of a bat ray over the course of two days just north of San Francisco. This particular ray started in one area, foraging, and then traveled to another area to forage, before moving on again.
Because bat rays are fairly common and prefer shallow coastal waters, we have opportunities to study their behaviors. Their mating behavior has been well documented, unlike many other species of elasmobranchs. During courtship, the male swims directly under the receptive female. He has a special set of thorns around his eyes that poke into the female’s belly and help to keep the pair bonded during the encounter. When they are aligned, the male twists a single clasper up and into the female’s cloaca and deliver’s his sperm package. The two separate and the female incubates a litter of up to 12 pups inside her for 9 to 12 months (Tricas et al., 1997). Bat rays give birth to live young, but the pups incubate inside individual egg sacs, attached to egg yolks, inside mom. It’s a process called ovoviviparity or aplacental viviparity.
Authority: Gill, 1865
Family: Myliobatidae, 42 species
Length: Disc width up to 6 feet (1.8 m)
Weight: up to 200 lbs (91 kg)
Habitat: Marine intertidal regions, estuaries, bays, coastal waters
Depth: Surface to 590 feet (180 m)
Gestation: 9 – 12 months
Litter Range: Up to 12 pups
Home Range: Western coast of North America from Baja California, Mexico to Oregon
Diet: Benthic animals with hard exoskeletons like crustaceans and bivalves
IUCN Status: Least Concern; sometimes taken as bycatch in commercial fisheries
(van Hees et al., 2015)
Thanks so much for checking out the bat ray! Remember to swim over to last week’s featured species: the Green Sawfish. If there is a species of shark you’d love to know more about, leave me a comment or send me a message! I would love to do a feature on your favorite species.
The new Ocean For Sharks Shop is open! There’s handmade ocean inspired plush animals, canvas paintings, and of course my children’s book, Winifred the Wondrous Whale Shark, available in print and PDF. Be sure to stop by. Remember proceeds benefit shark research and conservation with a donation to Project AWARE!
Conservation legislation needs public support in order to become law and help protect the environment and wildlife. Tell your representatives that you care about environmental and wildlife conservation. It only takes a moment to make a change that will last a lifetime. Until next time finatics!
Featured Image Source
Reitsma, A. (Photographer). (n.d.). Bat ray in a touch pool at the Aquarium of the Pacific [Digital Image]. Retrieved from http://www.aquariumofpacific.org/
Ebert, D. (2003). Sharks, rays, and chimaeras of California(No. 71). Univ of California Press.
Klimley, A. P. (2013). The biology of sharks and rays. University of Chicago Press.
Leet, W. S. (2001). California’s living marine resources: a status report. University Of California, Division of Agriculture and Natural Resources; Califorinia Sea Grant.
Tricas, T. C., Deacon, K., Last, P., McCosker, J. E., Walker, T. I., & Taylor, L. (1997). The Nature Company Guides: Sharks and Rays. (L. Taylor, Ed.). Hong Kong: The Nature Company, Time Life Books.
van Hees, K., Pien, C., Ebert, D.A., Cailliet, G.M. & Smith, W.D. (2015). Myliobatis californicus: the IUCN Red List of Threatened Species 2015. Retrieved from http://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T39416A80677869.en