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The Explorer's Guide contains a treasure trove of aquatic science resources developed for use in K-12 classrooms. Back to Explorer's Guide.


Whitetip Reef Shark Scientific Name: Triaenodon obesus
Most sharks need to swim in order to breathe. Sluggish whitetip reef sharks spend much of their day resting on the bottom. So how do they breathe? While taking it easy, these sharks pump water across their gills.



Region: Philippines


Appearance
While the whitetip reef shark is a requiem shark (member of the Family Carcharhinidae), it does not share many of the same characteristics of its family members. Often mistaken for the bigger, more graceful oceanic whitetip shark, the leaner whitetip reef shark is a small sluggish shark. Whitetip reef sharks can be up to 7 feet (2.13 m) long, but are rarely more than 5.5 feet (1.6m). They can weigh up to 100 pounds (45 kg). This fish is easily recognized by its coloration. The back and tail (dorsal and caudal) fins have distinctive white tips. Like most sharks, the whitetip reef shark exhibits countershading. This means the shark has a dark-colored back (gray to brown with dark spots and splotches) and a light-colored belly. When viewed from below, the whitetip blends in with the brightness of the sunny waters above. Viewed from above, the shark blends in with the dark ocean bottom. Countershading camouflages the animal, allowing it to sneak up on unsuspecting prey.

Whitetip reef sharks have a distinctive short, broad snout or nose and a flattened head. Mid-sized teeth fill this shark's mouth. The upper teeth are triangular and serrated or saw-toothed and the lower teeth are long, thin and dagger-like.


Habitat
Sticking close to shore, these sharks live in lagoons and seaward reefs or reefs closer to the open ocean than the shore at depths of 26 to 130 feet (8 to 40 m), but can also be found as deep as 1,110 feet (330 m). Here it is often found resting in caves or under coral ledges during the day. Sometimes whitetips even gather together in these areas, lying alongside and on top of one another. At night, they wake to search for food. After these nocturnal or nighttime attacks, individuals often return to the same resting place.


Range
Found on the other side of the world, whitetip reef sharks inhabit the Red Sea, Indian Ocean, and many areas in the Pacific.


Diet
Whitetip reef sharks eat fish such as eels, parrotfish, goatfish, snappers, damselfish, surgeonfish, and triggerfish. They will also eat crabs and lobsters and octopuses.

Most sharks efficiently hunt down their prey with great speed and finesse. They can also squirm into reef holes, trapping prey inside. Twisting and turning into reef holes and crevices to get at hiding prey, a hungry whitetip reef shark won't stop at anything to get a meal. If the prey escapes out another hole, this shark will swim fast and furiously, often cracking off large pieces of coral in a high-speed chase.


Reproduction
Of the three different ways that sharks reproduce, whitetip reef shark are live-bearing, or viviparous, fish. This advanced reproductive ability gives us a clue that these sharks are highly developed animals. Inside the uterus, each embryo is enclosed inside a separate membrane. The embryos attach to an egg yolk and leach nutrients from the yolk until birth. The babies or pups are born when they are old enough or large enough to survive on their own. Whitetips bear litters of one to five pups or baby sharks. The gestation period lasts at least five months, but can be as long as 13 months. When born, the pups are 20 to 24 inches (50 to 60 cm) long.


Endangered
>A species or group of organisms that is in danger of extinction or disappearing from the face of the earth in the near future if its situation is not improved.

Threatened
A species that can be found throughout its natural range but is declining in number and may become endangered in the absence of special protection efforts.

Vulnerable
A species that is not declining in number but is of special concern because it is sensitive to pressure by particular human activities or natural events.

Stable
A species that is not declining in number and is not sensitive to pressures by human activities or natural events.

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Threats and Management
Whitetip reef sharks are found in large numbers on reef, but people aggressively hunt whitetip reef sharks for their meat and liver, putting these sharks in the vulnerable category.

Sharks play a crucial role in reef and ocean ecosystems. They prey on weak and diseased animals. Human choices and human interference cause their numbers to decline. Some countries manage their coastal waters to protect sharks. But others have lax fishing laws, or too few resources to enforce laws that exist. In these places, shark populations suffer.

Sharks also suffer in the popular media, which often portray them as people-eating monsters. In reality, sharks don't attack people very often. When they do, it may be because they've mistaken a person for some other prey. Each year, sharks kill an average of eight people worldwide—yet people kill millions of sharks. Affecting the well-being of the entire reef ecosystem.

Fishing boats search the seas for target animals, like tuna, and discard anything else they accidentally catch—like sharks. The unwanted animals, called by-catch, dry out or suffocate on the deck, or get thrown back into the ocean all but dead. Each year, the worldwide fishing industry discards about a third of its total catch. This waste, or by-catch, not only pollutes the ocean but also creates extra work on fishing boats and ruins nets.

Sharks reproduce slowly, bear few young at a time, have a long gestation period, and many swim great distances to find a mate. That's why it takes years for their populations to rebound after a serious decline from overfishing.
FAO (Food and Agriculture Organization of the United Nations) member countries have been working for about a decade to create a plan of action for the conservation and management of sharks throughout the world. Many participating countries have been successful in their efforts. However, the vast size of the ocean and the lack of law enforcement in many areas maintain poor conservation and management of sharks globally.


Did You Know?
These sharks have also been referred to as weasel sharks due to their ability to squirm their way into confined reef holes and crevices.

While many sharks have no predators, whitetip reef shark fall prey to larger sharks like the tiger shark and bulky reef groupers like the Queensland grouper.

Whitetip reef sharks are one of the most abundant shark species on the reef.

The liver of the whitetip shark has been reported to be toxic.

It is estimated that whitetips live for about 25 years.

Whitetip reef sharks are very curious. In the wild, they will follow reef divers, spearfishers, free-divers and boats. People are often scared by a visit from these sharks, but they are not a threat. Most cases of attack occur after a spearfisher has just speared a fish. Other attacks have resulted from divers who try to pet or feed this nosy shark. People stand a greater chance of choking on a toothpick, getting struck by lightning or even being bitten by another person than getting attacked by a shark.


References
Web Sites:
NOTE: The following Web sites are not maintained by the John G. Shedd Aquarium and will open in a new browser window.

Fishbase:
http://www.fishbase.org/Summary/SpeciesSummary.cfm? genusname=Triaenodon&speciesname=obesus

Ichthyology at the Florida Museum of Natural History - Sharks: http://www.flmnh.ufl.edu/fish/sharks/sharks.htm

Print Publications:
Michael, S.W. 1993. Reef Sharks & Rays of the World. A guide to their identification, behavior, and ecology. Petaluma, California: Sea Challengers. 107p. ISBN# 0-930118-18-9.

Perrine, D. 1997. Mysteries of the Sea. Lincolnwood, Illinois: Publications International, Ltd. 312p. ISBN# 0-7853-2430-5.

Tricas, T.C., Deacon, K., Last, P., McCosker, J.E., Walker, T.I. and Taylor, L. 1997. Sharks & Rays. The Nature Company Guides. McMahons Point, Australia. 288p. ISBN# 0-7835-4940-7.


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Vocabulary Words

By-catch - The part of that part of the fisher's catch which is returned to the sea either because it has no value to them. Fishing boats search the seas for target animals, like tuna, and discard anything else they accidentally catch-like sharks. The unwanted animals, called by-catch, dry out or suffocate on the deck, or get thrown back into the ocean all but dead.


Caudal - Having to do with the end or tail of an animal. The tail fin.


Countershading - A form of camouflage in which an animal has a dark-colored back and a light-colored belly. Using fish as an example, when viewed from below, a fish blends in with the brightness of the sunny waters above. Viewed from above, the animal blends in with the dark ocean bottom. Countershading camouflages the animal, allowing it to sneak up on unsuspecting prey or hide from predators.


Dorsal - The back of an animal. The large fin on the back of a shark; the fin that sticks out of the water when a shark swims near the surface.


Extinction - An organism that has not been present on the face of the earth for over 50 years.


Gestation - The period of development of the young in viviparous animals, from the time of fertilization of the egg until birth.


Nocturnal - Active at night.


Organism - A living thing.


Overfishing - The excessive fishing or catching of aquatic (ocean or freshwater) animals to the point that the amount of animals being caught is greater than the amount of animals born. When more animals are caught than are being born, the aquatic environment is left depleted of the targeted animals.


Pet trade - An industry or business in which animals are taken from the wild and sold to pet stores, zoos, and aquariums.


Pup - A baby shark.


Seaward - Closer to the open ocean than the shore.


Serrated - The edges of the teeth have small teeth like those on a saw; jagged-edged having saw-like notches along the edge.


Snout - The pointy part of the head; similar to our nose.


Species - A group of organisms capable of breeding and producing fertile offspring; organisms that share the same gene pool.


Viviparous - A form of reproduction in which the young, or in this case pups, develop inside the mother. Each pup receives food from the mother's blood through an umbilical cord. The pups are born fully developed and able to hunt and swim on their own. This form of reproduction is referred to as "live birth".


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Whitetip Reef Shark
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