This week’s featured species is one of my favorite’s: the Common Thresher Shark (Alopias vulpinus). The common thresher is also known by a handful of other names, including fox shark, sea fox, swiveltail, and thrasher (Jordan, n.d.). For those whose Latin is a little rusty, “vulpinus” is derived from “vulpes” which means “fox.” These sharks may be named so because of their large eyes and short snouts. But the most distinguishing feature of the Alopiidae family is their tails (Parker, 2008). Many species of sharks exhibit uneven caudal lobes, called heterocercal (Parker, 2008), however, all three species of thresher sharks have extremely elongated upper lobes of the caudal fin that can measure as long as their bodies (Skomal, 2016)!
There are three species of thresher all belonging to the family Alopiidae:
- Common Thresher (Alopias vulpinus)
- Big-eye Thresher (Alopias superciliosus)
- Pelagic Thresher (Alopias vulpinus)
Of the three, the common thresher is the largest, sometimes reaching lengths of 20 feet from head to the tip of the tail (Parker, 2008). The common thresher has a moderate eye size, as like most pelagic species, they hunt by eye sight and smell first before using their additional senses (Skomal, 2016). They are generally slate grey or brown in color, however they have been found to be completely black (Jordan, n.d.). This darker top allows them to blend into the depths when viewed from above (Parker, 2008). Their under bellies have several dark spots near the caudal fin, but are otherwise white to blend in with the surface light when viewed from underneath (Parker, 2008; Jordan, n.d.). When viewed from the side, their counter shading offsets the sun’s lightening of the upper side and the shadowing effect on the under belly allowing the shark to seemingly disappear in the open water (Parker, 2008).
These amazing predators hunt like no other shark. Working in pairs or groups, they herd schools of fish, like herring or mackerel, or cephalopods together into bait balls (Parker, 2008). Then suddenly, their sickle-like tail whips forward and stuns their prey as they rush in to take the bait (Skomal, 2016; Parker, 2008). In these feeding frenzies, they have been known to hurdle prey and themselves high above the water (Parker, 2008). While they are considered harmless to humans and divers generally describe their behavior as non-aggressive, they should be always treated with caution and respect (Tricas, Deacon, Last, McCosker, Walker, Taylor, 1997).
Discovery Channel Southeast Asia (13 June 2016). Thresher Sharks Kill Prey With Tail Like A Whip | SHARK WEEK [Video Clip]. Retrieved from https://www.youtube.com/watch?v=ANjYYXIl_C8
Family: Alopiidae; 3 species in this family
Length: Up to 20 feet (6 m) measuring head to the tip of the tail
Weight: Up to 900 lbs (272 kg)
Habitat: Continental and island shelves and slopes; coastal and oceanic waters
Depth: Typically observed at the surface, however been known to inhabit waters up to 1,800 feet (500 m)
Gestation: 8-10 months
Litter Range: 2-6 pups per litter averaging 3.7 to 5.0 feet (1.1 to 1.5 m) long at birth
Home Range: Tropics to temperate waters worldwide
Diet: Schooling bony fishes such as herring and mackerel; Invertebrates such as squid.
IUCN Status: Vulnerable
(Skomal, 2016; Parker, 2008; Goldman, et al., 2009)
Thanks for checking out this week’s Featured Species! If you missed last week’s Featured Species, be sure to check out the Ornate Wobbegong. What species do you want to hear more about? Let me know by leaving me a comment! 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.
Featured Image Source
World Land Trust (n.d.) Thresher Shark [Digital Image]. Retrieved from http://www.worldlandtrust.org/images/animals/thresher-header.jpg
Goldman, K.J., Baum, J., Cailliet, G.M., Cortés, E., Kohin, S., Macías, D., Megalofonou, P., Perez, M., Soldo, A. & Trejo, T., 2009. Alopias vulpinus. The IUCN Red List of Threatened Species 2009: e.T39339A10205317.
Jordan, V. (n.d.). Alopias vulpinus. Retrieved July 08, 2017, from https://www.floridamuseum.ufl.edu/fish/discover/species-profiles/alopias-vulpinus
Parker, S. (2008). The encyclopedia of sharks (2nd ed.). Buffalo, NY: Firefly Books Ltd.
Skomal, G. (2016). The Shark Handbook: The Essential Guide for Understanding the Sharks of the World. (2nd ed.). Kennebunkport, ME: Cider Mill Press.
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.