Photo Source: National Park Service
For this week’s blog post, we will explore the world of bat rays! Although, in my opinion, sharks reign supreme in the ocean...there are other incredible members in the Chondrichthyes group. Chondrichthyes is a group of marine creatures that includes sharks, skates, rays, and chimaeras. They are considered cartilaginous fish and have hard scales, a pair of nostrils, a two-chambered heart, paired fins (NH-PBS). If you want to learn more about chimaera, check out our previous blog post, “We Are Family, I Got Chimaera With Me.”
Photo Source: Oregon Coast Aquarium
The bat ray, Myliobatis californica, is sometimes referred to as the “eagle ray” because they are in the eagle ray family, Myliobatidae. They are closely related to common eagle rays and spotted eagle rays. Their beautiful pectoral fins have flexibility and curvature that enables them to glide, propel, and swim with a bat-like appearance. Their tails look whip-like and have venomous spines. Generally, bat rays are docile and calm in nature but their venomous spines can be utilized for defense from predators. These rays’ wingspans can be up to 6 feet in length and a bat ray can weigh 80-200 pounds.
Bat rays are found on the bottom of the ocean where they forage for food. Generally, they are found in muddy waters, sandy waters, and kelp forests along the Oregon coast and south to the Gulf of California. As they traverse through the sandy ocean floor, they use their sense of smell to search for food. Their mouth is located on the underside of their body and they use their sharp teeth to crush any prey they find to consume. Their teeth are fused into strong, flat plates so that they can eat a variety of difficult prey. Similar to sharks, bat rays have readily available teeth to replace broken ones and these new teeth will grow in place when needed!
Photo Source: The University of Washington
Their diet consists of mollusks, crustaceans, and small fishes. They will crunch up their prey, eat the fleshy parts of it, and spit out the shell and non-digestible pieces. To find their prey, bat rays use an electrosensory organ called the ampullae of Lorenzini. Sharks have this organ as well (shown on the right). The ampullae of Lorenzini are tiny, porous openings on the underside of the body. They allow bat rays to detect electrical fields around them. These fields are detectable via the muscles and nerves of other animals in the area. To learn more about the ampullae of Lorenzini, click here for a short Youtube video.
Rays of Sunshine
One of the most valuable adaptations that the bat ray possesses is countershading. Countershading is seen in various places and ways throughout nature, and the bat ray is no exception to it. Countershading is a unique type of camouflage that allows an animal to be hidden, or somewhat disguised, from multiple angles and perspectives. The bat ray’s underside is very white and light which allows it to blend in with the lighter and upper part of the ocean. This is helpful for the bat ray’s camouflage from the lower perspective such as one looking up at a bat ray with the sun shining above. Additionally, the top of their body is a darker gray or brown which blends in with the ocean floor if predators or prey are viewing the bat ray from above, looking down on them.
Bat rays are solitary animals seen alone for most of the time, except for breeding season. Occasionally, they can be found in groups of thousands of individuals! They remain inconspicuous to predators and prey by hiding underneath the sand. Another adaptation they have is the ability to avoid ingesting sand. They do this with their adapted spiracles. A spiracle is an opening on the outer part of the body that serves as a breathing pathway. In the bat ray’s case, their first gill slits changed and evolved to create their spiracles. As water passes through their respiratory spiracles, it travels over their gills and then gets pushed out the underside of their body via gill slits (Aquarium of the Pacific).
Make Their Day, Save A Ray
Today, bat rays are considered least concerned. However, there are still important conservation topics to discuss with them. They are hunted and consumed for meat in Mexico and commercially fished there. When they are not hunted for meat, they are sometimes intentionally caught due to their active nature in nets. This reminds us to cut out seafood or eat sustainable seafood, and to support sustainable seafood practices.
Additionally, they were previously trapped and hunted by oyster farmers because they were thought to be destroying and eating all of the oysters and thus the farmers’ livelihoods. After research, it was found that these bat rays prefer crabs over oysters and the lack of their presence destroyed oyster areas because crabs were uncontrolled and able to move in and consume all of the oysters. I hope you learned something cool about bat rays, and share our blogs to help spread awareness!
Photo Source: Aquarium of the Pacific
Written By: Bailey Higa