Not just a
huge collection of
Elasmodiver.com contains images of sharks, skates, rays, and a few
chimaera's from around the world. Elasmodiver began as a simple web
to help divers find the best places to encounter the different
species of sharks and rays that live in shallow water but it has
slowly evolved into a much larger project containing information on
all aspects of shark diving and shark photography.
now more than 10,000 shark pictures and sections on shark
evolution, biology, and conservation. There is a large library of
reviewed shark books, a constantly updated shark taxonomy page, a
monster list of shark links, and deeper in the site there are
numerous articles and stories about shark encounters. Elasmodiver is
now so difficult to check for updates, that new information and
pictures are listed on an Elasmodiver Updates Page that can be
Examples of whiptail stingrays: The Cowtail Stingray
Hypolophus sephen and the Blue Spotted Fantail Ray Taeniura lymma
The family Dasyatididae which is commonly referred to as the Whiptail
Stingrays consists of 6 genera with at least 60 (and possibly over
100) valid species.
Below is a key to pinpointing the genera of Whiptail Stingrays:
No tail sting. Dorsum densely covered in tubercles (raised
denticles giving a prickly appearance) =
Urogymnus. Tail sting present. Tubercles sometimes present
but less numerous and pronounced = go to 2.
Rhomboid to oval disc. No finfolds on tail =
Himantura. Finfold present = go
Rhomboid Disc. Ventral finfold not as high as tail above it
and sometimes inconspicuous before close examination =
Pteroplatytrygon. Ventral finfold deep
= go to 4.
Disc rhomboid. Ventral finfold much higher than tail above
it = Hypolophus. Disc round or
oval = go to 5.
Round or oval disc. Ventral finfold reaching tip of tail:
Most Whiptail Stingrays have a very similar body plan with drab uniform
coloration making identification in the wild rather difficult. Some
species however, have a more easily distinguished dorsal pattern e.g.
leopard-like spots, small blue spots, blotches, a honeycomb pattern, or a
line of white spots running along each side of the disc. Other physical
clues to identification include:
The length and sturdiness of the tail in relation to disc length and
width. Note that this can be misleading as portions of the tails of
Whiptail Rays are often missing.
The number and position of tail stings present.
The presence or absence of tubercles running down the centre line of the
tail and/or covering the disc.
The shape of the snout e.g. rounded, angular, or elongated.
The overall shape of the disc and the angle of the anterior margin e.g.
rounded or rhomboid (diamond shaped / kite shaped).
The presence and depth of finfolds on the tail.
Whether the eyes are protruding or flush with the disc.
Habitat, depth, and geographic region are also useful in determining
Habitat and Geographic Distribution
Most Whiptail Stingrays are confined to marine habitats but some are known
to migrate into brackish estuarine environments and a few species are well
adapted to live year round in both fresh and salt water. The Atlantic
Stingray Dasyatis Sabina can be found in the Gulf of Mexico but
some colonies of D.sabina permanently inhabit fresh water
rivers and lakes in Florida. Other species such as Himantura chaopraya
(an enormous species from Thailand) is believed to live exclusively in
fresh water river systems.
Whiptail Stingrays are benthic rays that spend a great deal of time buried
under the sand or mud with just their eyes protruding. This is considered
primarily a defensive strategy rather than a stealthy way to surprise
prey. Because they tire easily when swimming, remaining buried is
the ideal way to avoid becoming lunch. Whiptail Stingrays are heavily
preyed on by a number of shark species (especially by hammerheads).
An exception to the benthic lifestyle is the Pelagic Stingray Dasyatis
violacea. Although this ray can also be found on the substrate it is a
free swimming ray that preys on oceanic squid and mid water fishes which
it manipulates by holding them between its pectoral fins. Because of its
unique behavior the Pelagic Stingray is sometimes categorized in its own
genera - Pteroplatytrygon.
Whiptail Stingrays generally inhabit shallow coastlines down to 100 or 200
meters but some species can be found at 600 meters or more.
All Whiptail Stingrays are ovoviviparous. (A mode of reproduction in which the embryo is contained within a membranous egg
case. Upon hatching the embryonic ray remains within the oviduct until fully
developed but a placenta is not formed directly to the wall of the uterus). Two
mating postures have been witnessed. One in which the rays coupled ventrum to ventrum, and another in which the male whipray mounted the the
Whiptail Stingrays have a varied diet. Depending on availability they are
known to eat: mollusks, crustaceans, jellyfish, and bony
fishes. The recorded stomach contents of one Honeycomb stingray included:
8 threadfin bream, 3 mackerel, 8 ponyfish, 8 cardinalfish, 3 sardines, 3
anchovies, 2 flatfish, 1 mojarra, 4 flatheads, 3 pufferfish, 5 squids, 2
crabs, and 2 mollusk shells!
Generally whiprays extract food by digging in the sand as illustrated by
this Southern Stingray.
Whiptail stingrays are known to gather at fishermen's fish cleaning
stations to take advantage of the scraps that end up on the seabed. In
some locations such as Stingray City in Grand Cayman and Hamelyn Bay in
Western Australia, their tolerance for humanity has reached the point
where they will eagerly accept scraps straight from the hands of tourists.
Although these interactions have altered the stingrays natural behavior
there is no evidence that they have lost the ability to hunt on their own.
Stingray City tours are now a multimillion dollar industry that attracts
hundreds of tourists daily. Although the large Southern Stingrays get
quite aggressive while they are competing for handouts of squid, they
rarely harm the
tourists, preferring to back off when trodden on rather than use their
defensive tail stings.
Traditionally stingrays were feared by fishermen and beach goers alike so
the positive press that the rays receive from these encounters is a
welcome change that may be a critical factor in their future survival.
Defensive Mechanisms and Treatment of Stingray
Most Whiptail stingrays carry one or more stingers or tail spines on the
top of their tails. The stinger is a modified dermal denticle that has
evolved into a weapon capable of puncturing the hide of a menacing
predator. It is sheathed in a mildly venomous covering of skin which is
pushed back as the point enters the victim allowing the venom to come in
contact with the cut tissue. Wounds inflicted by these stingers are
apparently very painful but the toxins can be broken down quickly with
heat. Treatment of a stingray wound should involve immersing the affected
area in water as hot as the victim can tolerate. The wound should also be
irrigated to ensure that no part of the spine has broken off. Infections
are common and where medical attention was not available stingray wounds
have resulted in fatalities.
Whiptail stingrays use their stinging defense to ward off predators. They
can curl their tails over their backs to sting forwards rather like a
scorpion. The effectiveness of this defense is debatable considering that
some Great Hammerhead Sharks have been found with more than 50 stingray
spines lodged in their throats with no sign that it had impaired their
ability to eat. Conversely, one diver witnessed a ray use a similar
defensive posture to effectively ward off a Great White Shark but it
is impossible to know if the White Shark was truly interested in eating
Whiptail stingrays are able to swim forwards (and slowly backwards) by
undulating their pectoral fins that form their body disc. See:
Elasmobranch Locomotion. Their
tails with their vestigial caudal finfolds may be used for steering
and balance but also support the defensive tail sting. It is possible that
Whiptail Stingrays also sacrifice the filamentous tip of their tail to
gain precious seconds to escape when being pursued by a predator.
Whiptail Stingrays spend a large percentage of their time buried with just
their eyes showing.
Their mouths and gills (like almost all rays) are positioned under their
bodies which makes breathing while on the sand rather challenging. To
overcome this hurdle they have developed extremely large spiracles
(spiracles are the openings positioned just behind the eyes through which
a shark or ray can suck in oxygen rich water to flush over the gills).
Through this mechanism Whiptail Stingrays are able to remain motionless
for hours at a time. Surprisingly, there is very little sand movement
where the water exits on the underside of the ray.
Whiptail Stingrays are known to attend cleaning stations where cleaner
fish can sometimes be seen entering their spiracles to remove parasites.