This week’s Featured Species is a species that divers in the Indo-Pacific often find resting during the day under coral reef shelves or in caves. But at night, these seemingly timid sharks turn into the wolves of the reef. This week we are taking a closer look at the Whitetip Reef Shark (Triaenodon obesus). This species is a member of the Carcharhinidae family (shown below as the Carcharhiniformes family), which first appeared in the fossil record around 63 million years ago (Aquarium of the Pacific, n.d.). The first evidence of the whitetip reef shark appeared around 42 million years ago (Aquarium of the Pacific, n.d.). To put that into perspective, when whitetip reef sharks first made their appearance in the fossil record, the first whales were also evolving from large land mammals that returned to the sea (Paleogene Period and the Beginning of the Cenozoic Era, 2017)!
The whitetip reef shark is almost exclusively found on coral reefs in the Indo-Pacific region. They are rarely ever observed on reef flats or in very shallow waters (Stevens, 1997). These sharks are often found by divers under rocky coral ledges or in caves during the day, sometimes resting in piles on top of reach like puppies. These packs of sharks are referred to as a shiver (Parker, 2008). Like dogs, or any other social animal, the whitetip reef sharks, also maintain a social hierarchy through displays of health, strength, and rarely through threats and physical combat. When these whitetips combat each other for social dominance, they have been observed headbutting each other with their mouths open. They sometimes inflect minor wounds on each other, but have not been observed full on attacking each other (Parker, 2008). These social groups can stay together for years. Tagging studies have shown that the whitetip reef sharks are strongly attached to their particular are of reef, often staying in the same area for many years (Stevens, 1997).
During the day, whitetip reef sharks appear sluggish. But once the sun goes down, these hunters dominate the reef. Unlike other requiem sharks, they are poor are hunting in the open water, however they have been highly skilled at trapping prey inside crevices in the rocky corals and using their blunt snouts to retrieve their prey (Tricas, Deacon, Last, McCosker, Walker, Taylor, 1997). What also makes the whitetip reef shark so formidable to any reef fish is that they hunt as a pack. Very few sharks hunt together. But the whitetip reef sharks turn dinner into a true feeding frenzy (Tricas, et al., 1997).
BlueWorldTV [Jonathan Bird’s Blue World]. (2015 May 7). Night of the Hunting Sharks! | Jonathan Bird’s Blue World [Video Clip]. Retrieved from https://www.youtube.com/
Whitetip reef sharks are relatively small, only about 7 feet (2.1 m) at maximum length. This leaves them vulnerable to being preyed upon by other large predators, including other sharks and large grouper fish (Epinephelinae) (Frederico & Hassall, 1998; Tricas, et al., 1997). In fact, there have been several documented cases in Asian aquariums where whitetip reef sharks have been consumed by their tank mates, sand tiger sharks (Carcharias taurus) (Reuters Media, 2016). But you wouldn’t want to try whitetip! While these sharks are often caught for commercial fisheries and consumed by humans for their flesh and liver, they are one of unique sharks that are able to cause ciguatera toxin poisoning- a type of food poisoning that can cause nausea, pain, cardiac, and neurological symptoms (Tricas, et al., 1997)!
Authority: Rüppell, 1837
Family: Carcharhinidae; 59+ species
Length: 7 feet (2.1 m)
Weight: 44 lbs (20 kg)
Habitat: Shelves; island terraces, shallow coastal waters of coral reefs, lagoons & caves
Depth: 26 – 130 feet (8 – 40 m)
Reproduction: Placental viviparity
Gestation: 5 months
Litter Range: 1 – 5 pups
Home Range: Indian and Pacific Oceans
Diet: Bottom and reef dwelling fishes and invertebrates
IUCN Status: Near Threatened; commonly taken in commercial fisheries; population estimates unknown
(Skomal, 2016; Smale, 2005; Parker, 2008; Tricas, et al., 1997)
Thanks for tuning in for this week’s Featured Species! Hope you enjoyed the Whitetip Reef Shark! Let me know what you’d like to see in the future by leaving me a comment. Want to know more about a ray species? A weird shark species? Tell me! If you missed last week’s Featured Species, be sure to check out the Shortfin Mako (Isurus oxyrinchus).
The new Ocean For Sharks Shop is open! There’s handmade ocean inspired plush animals, canvas paintings, and of course my children’s book, Winifred the Wondrous Whale Shark, available in print and PDF. Be sure to stop by. Remember proceeds benefit shark research and conservation with a donation to Project AWARE!
Remember you can make a difference for marine ecosystems by calling your Congress man or woman and tell them that you care about the quality of our waters! Sharks, rays, and other marine organisms cannot speak or be represented in Congress. They need your voice. Get involved and stand up for sharks. Until next time finatics!
Featured Image Source
White Tipped Reef Shark Clip Art [Digital Image] (n.d.). Retrieved from http://designingflicks.com/
Aquarium of the Pacific. (n.d.). Whitetip Reef Shark. Retrieved August 09, 2017, from http://www.aquariumofpacific.org/onlinelearningcenter/species/whitetip_reef_shark
Frederico, L., & Hassall, G. (Eds.). (1998). Reader’s Digest Explores: Sharks (1st ed.). Reader’s Digest.
Paleogene Period and the Beginning of the Cenozoic Era. (2017, August 03). Retrieved August 09, 2017, from http://www.nationalgeographic.com/science/prehistoric-world/paleogene/
Parker, S. (2008). The encyclopedia of sharks (2nd ed.). Buffalo, NY: Firefly Books Ltd.
Reuters Media. (2016, January 29). VIDEO: Shark eats tank mate at South Korean aquarium. Retrieved August 11, 2017, from http://www.inforum.com/news/3935909-video-shark-eats-tank-mate-south-korean-aquarium
Smale, M.J. 2005. Triaenodon obesus. The IUCN Red List of Threatened Species 2005: e.T39384A10188990.
Skomal, G. (2016). The Shark Handbook: The Essential Guide for Understanding the Sharks of the World. (2nd ed.). Kennebunkport, ME: Cider Mill Press.
Stevens, J. D. (Ed.). (1997). Sharks (6th ed.). New York: Facts on File.
Tricas, T.C.; Deacon, K.; Last, P.; McCosker, J.E.; Walker, T.I.; Taylor, L. (1997). The Nature Company Guides: Sharks and Rays. (L. Taylor, Ed.). Hong Kong: The Nature Company, Time Life Books.