Featured Species: Bat Eagle Ray (Myliobatis californica)

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.

Myliobatis_californica_monterey_bay_aquarium
Pedersen, M. H. F. (Photographer). (2009 April 23). Bat rays (Myliobatis californica) at the Monterey Bay Aquarium [Digital Image]. Retrieved from https://commons.wikimedia.org/

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).

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Bester, C. (Photographer). (2018). Bat ray jaw [Digital Image]. Retrieved from https://www.floridamuseum.ufl.edu/

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.

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Fig. 14.6 Track of a bat eagle ray in Tomales Bay, just north of San Francisco in central California. The daytime positions of the ray on Day 1 are indicated by clear circles and the nighttime positions by solid circles. The former positions during Day 2 are denoted by clear squares. The clusters of closely spaced positions are likely associated with foraging and widely spaced positions forming a line indicate the ray is migrating from one prey source to another (Klimley, 2013).

 

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.

DDDB 191 bat rays mating sm
Bushing, B. (Photographer). (2006). Bat Rays Mating [Digital Image]. Retrieved from http://www.starthrower.org/

Ray Stats

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)

Reproduction: Ovoviviparous

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!

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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/

Literature Cited

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

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Featured Species: Daggernose Shark (Isogomphodon oxyrhynchus)

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Featured Species: Green Sawfish (Pristis zijsron)

 

 

 

 

 

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