Hilton Head is home to a number of varietal species of rays, one of the most visually interesting being the cownose ray.
During the spring over the past few years, there has been an abundance of these rays washing up along our Hilton Head shores. This is likely being due to the storms and strong currents. While it is an unfortunate event, cownose rays are abundant throughout the Western North Atlantic.
Cownose rays, Rhinoptera bonasus, are part of the eagle ray family. Their scientific name comes from the Latin terms meaning “winged-nose bison,” a sentiment to their appearance. These rays vary in size, growing from one foot to four feet across. Their upper bodies are dark brown, while their underbellies range from creamy white to yellow, but they’re most noted for their short snout and concave forehead, which resembles a cow. Their tail is twice as long as their body and contains a venomous barb for self-defense. When swimming close to the surface, these rays’ wing tips will stick out of the water, resembling dorsal fins on sharks.
These rays are abundant from Maine, all the way to Brazil.
They make great migrations up to two times a year. The spring finds them moving northward for warm summer waters, while the fall shifts their movements back south. A number choose to live in our South Carolina waters year-round. They are pelagic creatures, spending most of their time swimming in the water column. Feeding behaviors lead them to the bottom of sandy or muddy coastal waters.
They primarily eat bivalves – clams, mussels and oysters. They have sharp teeth that break apart the shell and stomachs that are able to digest the soft body tissue and send the shell refuse out of their gills. When looking for prey, cownose rays use electroreceptive locators, sending electric waves into the sand to see if disturbances reflect off of them. Once the buried prey is found, the rays will start a stirring motion with their wings, sucking and venting water and sediment through their gills. This process moves the sediment out of the steep sided cavity and away from the prey.
Reproduction can occur any time between May and October.
Cownose rays take a long time to mature, males usually at six years and females all the way up to eight years. Once fertile, females on average produce one young, once a year. Females will develop an egg inside of their body that will gestate for up to twelve months. The eggs will develop and then hatch within the female in an ovoviviparous reproduction cycle. The young are born live and come out tail first.
Cobia, sandbar sharks and bull sharks prey upon cownose rays, but they are able to use their venomous stingers as a form of self-defense. It is very unlikely for a person to be stung by a cownose ray because they spend most of their time in the water column, instead of the bottom of our coastal areas.
By: Master Naturalist, Kathleen McMenamin