Notes from the Field: The Bat Ray of the Marsh

bat ray
The fin of a Bat Ray in the Bay.

A tip of a fin poked out from the water. “Look at that!” I exclaim, looking up from the quadrat, where I was busily measuring plant heights during a day of monitoring at one of our restoration sites.

“Look at what?” my field partner replies.
“That,” I say, “Look at that,” I now say again excitedly as the other fin pokes out of the water.

“Oh… a bat ray,” he says as he spots it, letting his clipboard drop for a moment. This time, we both look away from our monitoring for a moment.  We watch as the bat ray glides along the shoreline, inadvertently exposing one fin out of the water while the other moved the bay mud beneath in search for breakfast, lunch and dinner.

The Myliobatis californica, otherwise known as the bat ray, is readily found in the San Francisco Bay. Traveling solitarily or in groups, bat rays can live in a wide range of salinities and can be found in the ocean, as well as the bay. Known to dig holes in the mud looking for their prey, which they create by suctioning their body on and off the sandy or muddy bottom, bat rays eat molluscs, crustaceans and small fish.  Chomping down things like whole crabs, shell and all, it spits out the hard parts, leaving only the fleshy inside for its eating.

Female bat rays are larger than male bat rays and can have a wingspan of up to 6 feet and weigh up to 200 pounds. Females get pregnant annually in the spring or summer and are pregnant for 9-12 months, with pups, or baby bat rays emerging from the mother live. A relative to sting rays, they too have a stinger or spine but are not known to sting unless in self-defense. Interestingly, pups emerge from their mothers with a built in sheath over their spine, which falls off shortly after birth.

Bat rays are known to jump out of the water and skim along the surface. I have yet to see this myself but fingers crossed, will someday. There are many spots that bat rays can be seen from the shoreline and Save the Bay’s restoration sites. Bat rays can be seen most easily by us along the shoreline at low tide. One good spot to look for them in Oakland is at the bridge that crosses over the outlet of New Marsh in the Martin Luther King Shoreline (check out our map). I can’t guarantee that you will see them here, but if you are patient, it is very possible, and it is definitely worth the wait.

Next time you volunteer with us, you might see a bat ray for yourself —

Crescent Calimpong, Restoration Specialist