The cownose ray (Rhinoptera bonasus) is a highly migratory eagle ray known for its large, schooling movements in coastal waters. Its common name comes from the unique shape of its head, where separated pectoral fins create a notched appearance resembling a cow’s snout. These rays use powerful, plate-like teeth to feed on hard-shelled organisms like clams and oysters, which impacts the local ecosystem. Understanding their location and movement is important for conservation and managing interactions with shellfish industries.
Global and Regional Distribution
The cownose ray is primarily distributed along the continental shelf of the Western Atlantic Ocean. Its range extends northward from southern New England, down the United States East Coast, and throughout the Gulf of Mexico. The species is also found in the southern Caribbean Sea and along the Atlantic coast of South America.
Specific populations reach as far south as Trinidad, Venezuela, Brazil, and Uruguay. The American cownose ray (Rhinoptera bonasus) is confined to the Americas, demonstrating adaptability to diverse temperate and tropical marine environments.
Specific Habitat Characteristics
Cownose rays are pelagic, but they regularly inhabit specific nearshore environments for feeding and reproduction. They prefer shallow coastal waters, bays, and estuaries, typically found at depths less than 72 feet (22 meters). Their tolerance for a wide range of salinities allows them to utilize brackish estuarine systems, such as the Chesapeake Bay, as seasonal nursery and feeding grounds.
The physical composition of the seafloor relates directly to their diet. Cownose rays seek areas with soft, muddy, or sandy substrates. This soft bottom allows the rays to use their snout and pectoral fins to forage, stirring up sediment to uncover buried prey like clams and crustaceans. They employ electroreception and mechanical stirring to locate and excavate food items from the benthos.
Annual Migration Patterns
The cownose ray is a highly social and migratory animal, performing long-distance, seasonal movements driven by changing water temperatures. In late spring and early summer, large schools migrate northward along the Atlantic coast, reaching the mid-Atlantic and northern states like New England.
This northward journey allows them to reach productive feeding and mating grounds, aggregating in coastal areas like the Chesapeake Bay during warmer months. In late fall, the rays reverse course, undertaking a southward migration to find warmer wintering grounds. Tagging studies show that rays along the U.S. East Coast travel to offshore waters near central Florida, such as Cape Canaveral, for the winter. The southward departure from northern estuaries is often tied to the sea surface temperature dropping, potentially triggered by a threshold around 72 degrees Fahrenheit (22 degrees Celsius).