TIGER SHARK Galeocerdo cuvier
Scientific classification
Kingdom: Animalia
Phylum:
Chordata
Class:
Chondrichthyes
Subclass: Elasmobranchii
Order:
Carcharhiniformes
Family:
Carcharhinidae
Genus:
Galeocerdo
Müller & Henle, 1837
Species:
G. cuvier Tiger shark
Binomial name
Galeocerdo cuvier
Péron & Lesueur, 1822
Tiger shark range
Synonyms
Squalus cuvier Peron and Lessueur,
1822
Galeocerdo tigrinus Müller and Henle,
1837
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Description
The tiger shark has many distinctive characteristics making it easy to distinguish from other
requiem sharks. It has a broad, flat head with a snout shorter than the width of the mouth, long
labial furrows, and a slender body. The caudal fin is long and pointed with reinforcing ridges
and its teeth have curved cusps with serrated edges and a deep notch on the outer margin.
Juvenile tigers up to 150-180 cm in length have a distinctive mottled pattern on their dorsal
surface. Striped tiger-like patterns or bars appearing on adult specimens are from spots fusing
together. These bars tend to become faded as the shark ages but remain apparent on the
flanks and caudal region. Color can vary from bluish or greenish gray to black above and light
gray to dirty yellow or white below.
Range
The tiger shark is a common large shark found worldwide. Off North America, it is usually
found on the east coast from Cape Cod to Florida and in the Gulf of Mexico and on the west
coast from California southward. It is commonly found off the Carolinas, Georgia and Florida
and is one of the most abundant large sharks found in the Caribbean. Tiger sharks have been
known to stray far outside their normal habitat range and are occasionally encountered by
offshore fishermen in Canadian waters during the summer months. They are typically caught
by Canadian fishermen while fishing for tuna and swordfish in or near the Gulf Stream.
Habitat
The tiger shark is often found in tropical and warm temperate waters. It inhabits both oceanic
waters (up to 140 m) as well as shallow coastal waters. They seem to prefer turbid coastal
areas where fresh water runoff occurs as different prey species may congregate to feed in
these areas. They have not been reported inshore in Canadian waters.
Life History
Specimens between 300 and 425 cm and 380 to 640 kg are commonly taken and the largest
specimens are believed to exceed 5.5 meters. Lifespan is believed to be about 27 years
Diet
The tiger shark is omnivorous and a voracious predator. It has been known to consume a
wide variety of marine prey and even some terrestrial animals. Common prey include crabs,
shellfish, lobsters, squid, bony fish, small sharks, skates, rays, porpoises, turtles, marine birds
and mammals. A large number of inorganic artifacts and garbage associated with humans
have been found in the stomachs of tiger sharks as well. With such a diverse range of prey,
the tiger shark is considered the most adaptable of all shark species.
Reproduction
The tiger shark is ovoviviparous; bearing 35 to 55 pups in a single litter. Gestation is
believed to last just over 12 months. Pups are generally 68 to 85 cm long at birth. The males
and females mature between 4 to 7 years.
Interaction with people
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The tiger shark is considered to be one of the most dangerous and aggressive shark species,
becoming very active when stimulated by food.
Distinguishing Characteristics
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Distinctive mottled pattern in juveniles, striped tiger-like pattern in adults
Cockscomb-shaped curved serrated teeth with deep notches on the outer margin
Snout shorter than the width of the mouth, large head and slender body
Long and pointed caudal fin with reinforcings
Tiger shark teeth (photo courtesy of Lisa J. Natanson).
g_cuvier-dent.jpg
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The Tiger shark is an example of a shark which evolved non-specific teeth for generalized feeding. it
has one of the most non-generalized dentitions in the shark world. It happens that it is an efficient and
large dentition allowing it to feed on a variety of prey items but then the Great white which has a
specialized dentition as well (marine mammals) also has a varied diet consisting of fish, sharks, squid,
as well as mammals.
The Tiger shark whose dentition has undergone relatively little change (except a marked
increase in size) since it evolved in the Eocene out of the Galeorhinus (tope shark)
linage.
If we look a tooth of the Paleocene praecursor of the tiger shark (Galeorhinus lefevrei) in
many ways it appears to much like that of the modern tiger shark (Galeocerdo cuvier)
except in minature. It lacks some of the details (the blade is not as recurved and there are no
secondary serrations on the cusplets) but these are minor details.
The following sharks (particularly Galeocerdo latidens and Galeocerdo eaglesomei)
even more closely resemble teeth from the modern shark.
The other tiger shark of this age eventually reached an evolutionary deadend withG. contortus in the Miocene but even here the resemblence to teeth of the
modern tiger is unmistakeable.
In the Oligocene the last ancestor to the modern tiger shark evolved, G. aduncus. This shark's
teeth are virtually identical to those of the modern shark except for size.
If compared with teeth from a modern juvenile shark, they are indistinquishable.
Ward & Bonavia (2001) argued that the teeth long ascribed to Galeocerdo contortus were
in fact those of the extinct genus Physogaleus.
This tooth-design is so similar to Physogaleus and dissimilar to Galeocerdo that it was
difficult to disagree with their conclusions.
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However, they went on to ascribe Agassiz's G. aduncus to Physogaleus then synonymized
contortus with aduncus.
Contortus - Galeocerdo contortus
Contortus shark teeth are similar to Tiger sharks', but the large crown has a twist to it, it is
contorted. This species is now extinct. Unlike the teeth of most miocene sharks, which are
found world-wide, contortus teeth are only known from the east coast of the US.
Was Lee Creek now without a Miocene tiger shark?
Ward (pers com 2003) indicated that there is still a Miocene tiger, but those teeth (looking
like small cuviers) can be differentiated from the Agassiz type for aduncus. This matter has
not been fully explained to the satisfaction of the authors (who don't agree amongst
themselves). For the time being, these two genera will be included on the same page.
Tiger shark teeth are abundant at the mine, particularly in the Pungo River. These teeth are very
useful because they can serve as index fossils when working mixed tailings. "Galeocerdo" aduncus
and Physogaleus "contortus" are Pungo River species and G. cuvier, a Yorktown species. P.
"contortus" teeth (usually worn) occasionally appear in the basal Yorktown -- these may be reworked
Pungo river teeth.
Finally in the late Miocene full scale teeth of G. cuvier are found.
G. aduncus
G. Contortus
G. Cuvier
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(lingual view) from the Pungo River. Largest tooth in the image: 21 mm wide
."Galeocerdo" aduncus (AGASSIZ, 1843)A very common tooth in the Pungo River
formation. It is very similar in appearance to G. cuvier but is much smaller and less
massive.Tiger sharks - Galeocerdo aduncus Tiger shark teeth have one large crown on
the anterior side, and many small serrations on the posterior side. This shark evolved in to the
modern day tiger shark, Galeocerdo Cuvier, which has almost identical, but larger teeth.
(lingual view) from the Yorktown.The largest tooth in the image is 32mm wide x 34 mm slant
height.
Galeocerdo cuvier (PERON & LESUER, 1822)It is very difficult to
distinguish uppers from lowers in tiger sharks, even in a modern jaw the uppers are virtually
indistinguishable from the lowers. Also note the tremendous variability in symphyseal teeth.
They may be symetrical or assymetrical and differ greatly in size even in the same shark.
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Tiger sharks also have a high percentage of pathologic teeth
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So the point is to say that the tiger shark's teeth changed to fit a new cosmopolitan diet
is not entirely correct. In fact, they have changed little except in size.
Now to say that the teeth are shaped for a cosmopolitan diet is also probably also incorrect.
The teeth are in fact specialized for feeding on sea turtles. Unlike the vast majority of sharks in
which the upper and lower teeth are noticeably different (typically - with many exceptions - narrow
lower and wider upper teeth, tiger shark teeth are so alike from both jaws that it is difficult to tell
uppers from lowers).
The teeth are also shaped like the cutting edge of a round-saw. Thus when the shark clamps down on
a turtle shell and begins to shake his head, his serrated, round-saw blade shaped teeth litterally
begins sawing through the turtle's shell, both on the top and the bottom. Compare this with a more
typical dentition such as that from a dusky shark (Carcharhinus obscurus).
With curved, roughly triangular serrated upper teeth and narrow, pointy lower teeth, biting into a turtle
presents a problem.
While the upper teeth would have an effective sawing bite. The narrow, pointy lower teeth would not.
Without an effective hold on the turtle, shaking its head might simply toss the turtle out of its mouth
and in any event, the upper teeth are going to have to do virtually all of the cutting work.
With a large, efficient cutting dentition, the tiger shark can feed on a wide variety of prey, but it is
adapted, designed, and specialized to feed on turtles.
Physogaleus "contortus" (GIBBES, 1849)
Another common tooth in the Pungo. This tooth is much thicker in cross section than "G".
aduncus and has a noticable twist (contorted) in the tip of blade when looking down along it.
Unlike "G". aduncus which may have continued to evolve into G. cuvier, "contortus" had
reached its high water mark. Extremely common in the mid-Miocene, by the late Miocene, it
was very rare and had become extinct by the Pliocene.
Physogaleus "contortus"
(lingual view) from the Pungo River formation.
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If you want an example of a less specialized dentition, I would use the one of the
Carcharhinus species such as the bull or dusky sharks as examples. With large, roughly
triangular upper teeth and narrow, pointy lower teeth, they feed on a wide
variety of prey.
In fact, so successful is this type of dentition that it or a close approximation is
found in dozens of species of sharks.
note:
In the late Cretaceous, a period famous for its large sea turtles, a genus of shark
(Squalicorax - crow sharks) evolved teeth along the same pattern as the modern tiger shark.
The teeth are of a remarkably similar size and shape as tiger shark teeth and even evolved
larger as time went on.
In fact, a few teeth of (Squalicorax pristodontus (the last and largest species) have fine
serrations on the edges of the coarse serrations, a pattern found virtually no-where else except
on tiger sharks.
The crow sharks were from a completely different family of sharks than the tiger sharks and
went extinct with dinosaurs, leaving no descendants.
Squalicorax pristodontus (Extinct Crow Shark)
These are extraordinarily large examples of an extinct Crow shark (Cretaceous 70 mya) . All teeth are extra
large, well preserved, and have great color. These Crow shark teeth are definitely not common in
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