Geographic Range
Nearctic, Atlantic Ocean, Neotropical:
The Southern Stingray has been found in the Nearctic waters as far north
as New Jersey, throughout the Caribbean, and in Neotropic waters as far
south as coastal central South America. The Southern Stingray is most
abundant, however, in Florida and the Bahamas (http://www.Caymans.com:8080/~Caymans/Stingray_City.html,
1996).
Physical Characteristics
Southern Stingrays are almost completely
flat. The entire body consists of a disc-shaped body with no distinct
head. At the end of the body is a long whip-like tail that contains one or
more razor-sharp serrated barbs.
The eyes and unusually large spiracles are
on top of the ill-defined head, and the mouth and gill slits are on the
underside. The sides of the Southern Stingray consist of large pectoral
fins, which are mistakenly, yet quite commonly, called "wings." Dasyatis
americana has no dorsal or caudal fin. The ventral surface of the ray
is always white with the top ranging from khaki to dark brown to slate
gray.
One of the distinct features to the class
Chondrichthyes is that the entire endoskeleton is made of cartilage. Bone
is completley absent from the entire class. This is an interesting fact,
espacially since the ancestors of the Chondrichthyes had well-developed
bone.
Females are the larger of the two sexes,
with a maximum width of six feet across. The average female, however, is
considerably smaller. The male adult can have as little as a two foot
fin-span (http://www.Caymans.com:8080/~Caymans/Stingray_City.html,
1966; http://www.Cayman.org:80/fauna/stingray.htm,
1966; Hickman and Roberts, 1995.)
Natural History
Food Habits
The Southern Stingray's main diet
consists of crabs, shell fish, marine worms, conch, shrimp, and
occasionally small fish.
The mouth of the Southern Stingray is
hidden on the flat underside, and it feeds by slowly grazing the sand of
the ocean floor. With the eyes on top side of the ray, it relies on
highly developed electro-receptors combined with an acute sense of smell
and touch. After the prey is sensed, the ray covers it with its body.
While feeding, the ray completely buries itself in the sand. Usually,
during this process, only the eyes and long tail are exposed. People
commonly mistake this feeding stage as a stage of sleep (http://www.Caymans.com:8080/~Caymans/Stingray_City.html,
1966; http://www.Cayman.org:80/fauna/stingray.htm,
1966).
Reproduction
The Southern Stingray participates in
internal fertilization. Dasyatis americana is ovoviparous; the
female carries eggs internally but does not nurture the fetuses. The
young hatch from the eggs while still in the mother's body. The ray
gives birth to approximately three to five, nine-inch long
"pups" born at the same time. The pups have long, spiny tails
and large fins like the adult, but the body is somewhat slimmer. To make
birth easier, the pup's spine remains flexible, and the
"wings" of the unborn ray remain folded over in the style of a
newspaper (Gilbert et al., 1967; McCormick et al., 1963; http://www.Caymans.com:8080/~Caymans/Stingray_City.html,
1966; Hickman and Roberts, 1995)
Behavior
Dasyatis americana has a poorly
developed social system. Most move actively through their environments.
An exception to this is the two "Stingray City" tourist
attractions in the Cayman Islands and the Bahamas, where large groups of
stingrays remain in the same spot because they get fed daily. Little is
known about any social structure within these aggregations.
Habitat
Dasyatis americana is a bottom
dweller. It lives in shallow bays, sounds, and in-shore waters on sandy
bottoms. It usually remains away from walls and large reefs where it is
difficult for it to feed (http://www.Cayman.org:80/fauna/Stingray.htm,
1966).
Biomes: benthic, temperate
coastal, tropical coastal
Economic Importance for Humans
Positive
Until 1987 the species was mostly
ignored. Since then, the stingray has become a major tourist attraction.
"Stingray City", located a few miles off Grand Cayman of the
Cayman Islands, is a main attraction. In 1996, a new and similar site
opened in the Bahamas. Now a major part of the tourism industry revolves
around visiting these creatures (http://www.Caymans.com:8080/~
Caymans/Stingray_City.html, 1996).
Negative
The Southern Stingray has the ability to
"sting" humans, and for this reason it is potentially
dangerous. When stepped upon, the ray lashes its tail up and attempts to
drive it into the intruder as a self-defense mechanism. The spines on
the stingray's tail cut and tear the flesh, and the ray also injects a
poison. Although not life threatening, the poison is a protein that can
cause depressed respiration. The stings can be extremely painful. More
serious stings result from the stingray than from any other species of
fish (http://www.Caymans.com:8080/~Caymans/Stingray_City.html,
1996; http://www.Caymans.org:80/fauna/Stingray.htm,
1996).
Conservation
Status: no special status
Dasyatis americana is plentiful
Other Comments
The Southern Stingray is often mistaken as
an aggressively dangerous animal. This misconception comes from a lack of
knowledge of the ray's anatomy and behavior. Dasyatis americana
does have razor-sharp serrated barbs located at the base of the tail. It
does contain a venom that can cause pain and swelling on contact. However,
rays are extremely unagressive creatures and they do not attack anything
with their tail. It is used soley as a defense mechanism. When swimming,
stingrays are not even capable of directing their tail and are relatively
defenseless. It is a very poor deterrent against the ray's main predator,
the shark, to which it is closely related.
Many native people of the Polynesia,
Malaysia, Central America, and Africa have used the spines of stingrays to
make spears and knives. In many cases these people would cut off the
entire tail to be used as a deadly whip (http://www.nwf,org.80/nwf/lib/rr/sting97.html,
1997; http://www.Caymans.com:8080/~Caymans/Stingray_City.html,
1996; http://www.Cayman.org:80/fauna/Stingray.htm,
1996).
|