| Cownose ray | ||||||||||||||
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| Rhinoptera bonasus (Mitchill, 1815) |
The Cownose ray (Rhinoptera bonasus) is a species of Eagle ray found throughout a large part of the western Atlantic and Caribbean from New England, USA, in north to Brazil in south. It is the most common type of ray found in the Chesapeake Bay, USA. The rays grow rapidly and male rays are about 35 inches (90 cm) in width and weigh 26 pounds (12 kg). Females are 28 inches (70 cm) in width and weigh 36 pounds (16 kg). When the ray is small it grows inside its mother, positioned with wings folded over its body. It also gains nutrition from the mother's uterine secretions. It also breaks through what is called a breech birth-tail first. The cownose ray is 11 to 18 inches (28 to 46 cm) in width at birth. When it gets older it can often grow to 45 inches (1.1 m) in width, and weigh 50 pounds (23 kg) or more. There is some controversy over the size an adult cownose ray can reach; however a wingspan of 84 inches has been recorded. It is brown-backed with a whitish belly. Ovoviviparous. Cownose rays don't have a particularly distinctive coloration but its shape is recognizable. Its eyes peer out spookily from the sides of the broad head. It also has a set of remarkable teeth plates designed for crushing clams and oyster shells. One can also be stung by a cownose ray. The stinger is on its tail, close to the ray's body, and it doesn't usually inflict damage. The stinger is known as the spine which is pointed and it has teeth lining its lateral edges. It is coated with a weak venom that posses symptoms similar to that of a bee sting. The cownose ray feeds upon clams. It is a voracious eater. They also eat oysters, hard clams and other invertebrates. The mouth is located on the underside. On the front, there are two modified fins which form a suction which allows the ray to vacuum up food from small cracks. Rays move as a group regardless of time during feeding. This group's synchronized wing flaps stir up sediment and allows the rays to find buried clams and oysters. When they locate their prey they place it in their jaws and crush it. In 2007, from June 2nd to September 1st, Brookfield Zoo featured an exhibit where visitors could reach into a wide but shallow pool containing mostly cownose rays who had their stingers docked, making them safe enough to touch as they swam around the pool. The Aquarium of the Americas in New Orleans, Louisiana, currently features a cownose ray touchpool and twice daily visitor feeding times.
References
- Barker (2005). Rhinoptera bonasus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Database entry includes a lengthy justification of why this species is near threatened
- "Rhinoptera bonasus". FishBase. Ed. Ranier Froese and Daniel Pauly. August 2005 version. N.p.: FishBase, 2005.
