Tiger Shark Prey and Predators
As we've mentioned, one of the most interesting things about tiger sharks is its diet. The tiger shark's diet changes as it ages. Small tiger sharks feast primarily on fish and sea snakes, but as they grow, their giant mouths and increased size allow them to catch larger prey. Studies have shown that the tiger shark has a very adaptable palate; in Hawaii, tiger sharks feast most commonly on sea birds, but in Australia, sea snakes are usually on the menu [source: Heithaus].
For the most part, tiger sharks feed on local marine species. One study that evaluated the contents of tiger sharks' stomachs found that dugongs, a mammal similar to the manatee, were present about 47 percent of the time. Sea snakes were found 60 percent of the time, and sea turtles were found in 27 percent of the sharks, although only in larger sharks [source: Heithaus].
But what gets people's attention is the wackier things that have shown up in a tiger shark's stomach. Rubber boots, bags of charcoal, boat cushions, hubcaps, pets, raincoats, handbags, cow's hooves, deer antlers, lobsters, a suit of armor, sneakers with legs attached…this list could go on for a while [source: McRae]. Scientists are still determining whether such a diet means that the tiger shark is primitive and unevolved in its willingness to eat anything, or whether being able to eat anything is a smart evolutionary defense [sources: MarineBio, Ritter].
Because tiger sharks live in warm waters, they're likely to make human contact, and sometimes people become the prey of the tiger shark. Because the tiger shark's appetite is so voracious, it's also less likely that they'll just try a nibble and retreat, as some other sharks do. According to the International Shark Attack File, the tiger shark has been responsible for 155 attacks on people since 1580, far behind the great white's 437 and edging out the bull shark's 110 [source: International Shark Attack File]. Together, these three sharks are responsible for 99 percent of attacks on humans, but these numbers shouldn't necessarily keep you out of the water. In Hawaii, for example, the odds of being attacked by a shark are about one in 5 million [source: Tennesen].
Tiger sharks have also been known to eat other tiger sharks, but they're not the only ones -- a tiger shark's fins are a hot culinary commodity in Asian culture. Shark fins provide the spaghetti-like noodles in shark-fin soup. In Hong Kong, a tureen of shark-fin soup costs $100 [source: McRae]. Fishermen eager to cash in on the high price of shark fins sometimes amputate the fins of sharks and then release them, which is a death sentence because definned sharks cannot swim fast enough to catch their prey.
Tiger sharks also are harvested for their flesh, which can be used to make leather, and for their livers, which have high levels of vitamin A and can be used to make vitamin oils. Tiger sharks are also among the sharks caught for sport by fishermen, and sometimes the government has sponsored the fishing of tiger sharks. In Hawaii in the late 1950s, after a spate of tiger shark attacks, a state-sponsored program provided $300,000 to rid the waters of tigers. As we learned in the last section, this might not be an effective way to catch the offending animal because tiger sharks don't usually stay in the same place for long. Because of these human threats -- tiger sharks have no other predators in the sea -- tiger sharks are listed as a near-threatened species by the World Conservation Union.
However, not everyone is out to get the tiger sharks. Scientists say that predators such as the tiger shark keep the ocean's ecosystem in balance, and in Native Hawaiian belief, tiger sharks are aumakua, or sacred guardian spirits.
If you'd like to learn more about tiger sharks, swim over to the links below.
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More Great Links
- "Dugong." National Geographic. (April 18, 2008)http://animals.nationalgeographic.com/animals/mammals/dugong.html
- "Galeocerdo cuvier, Tiger Shark." MarineBio.org. (April 15, 2008)http://marinebio.org/species.asp?id=37
- Heithaus, Michael R. "The biology of tiger sharks, Galeocerdo cuvier, in Shark Bay, Western Australia: sex ratio, size distribution, diet, and seasonal changes in catch rates." Environmental Biology of Fishes. 2001. (April 15, 2008)http://www.monkeymiadolphins.org/Pdf/Heithaus%202001.pdf
- "Is there a difference between tiger sharks and sand tiger sharks?" North Carolina Aquariums. (April 15, 2008)http://www.ncaquariums.com/askaquarium/tigers.htm
- "ISAF Statistics on Attacking Species of Shark." International Shark Attack File. Updated Jan. 29, 2008. (April 15, 2008)http://www.flmnh.ufl.edu/fish/sharks/Statistics/species2.htm
- Knickle, Craig. "Tiger Shark." Florida Museum of Natural History Ichthyology Department. (April 15, 2008)http://www.flmnh.ufl.edu/fish/Gallery/Descript/Tigershark/tigershark.htm
- Martin, R. Aidan. "Tiger Shark." ReefQuest Centre for Shark Research. (April 15, 2008)http://www.elasmo-research.org/education/ecology/coral-tiger.htm
- McCarthy, Terry. "Why Can't We Be Friends?" Time. 2001. (April 15, 2008)http://www.time.com/time/2001/sharks/cover.html
- McRae, Michael. "Misunderstood Predator." Equinox. September/October 1992. (April 15, 2008)
- "Requin." The Free Dictionary. (April 15, 2008)http://www.thefreedictionary.com/Requin
- "Rhincodon typus, Whale Shark." MarineBio.org. (April 18, 2008)http://marinebio.org/species.asp?id=47
- Ritter, Erich K. "Fact Sheet: Tiger Sharks." Shark Info. 1999. (April 15, 2008)http://www.sharkinfo.ch/SI4_99e/gcuvier.html
- Tennesen, Michael. "A Killer Gets Some Respect." National Wildlife. August/September 2000. (April 15, 2008)http://www.nwf.org/nationalwildlife/article.cfm?articleId=293&issueId=31
- "Tiger Shark." National Geographic. (April 15, 2008)http://animals.nationalgeographic.com/animals/fish/tiger-shark.html
- "Tiger Shark FAQ's." Sharklife Conservation Group. (April 18, 2008)http://www.sharklife.co.za/index.asp?Content=134
- Whitney, Nicholas M. and Gerald L. Crow. "Reproductive biology of the tiger shark (Galeocerdo cuvier) in Hawaii." Marine Biology. Sept. 26, 2006. (April 15, 2008)
- Wirsing, Aaron J., Michael R. Heithaus, Lawrence M. Dill. "Tiger shark (Galeocerdo cuvier) abundance and growth in a subtropical embayment: evidence from 7 years of standardized fishing effort." Marine Biology. Feb. 25, 2006.