It’s that time again when I gush over this week’s Featured Species! This was the first shark I ever worked with in the field and they have always had a special place in my heart- even before that beautiful moment!
This week’s Featured Species is the nurse shark (Ginglymostoma cirratum). These beautiful sharks are often found at the bottom of the sea floor, resting under coral reef ledges. While the nurse shark spends the majority of the day resting, they are mostly active at night (Parker, 2008; Skomal, 2016). Like most sedimentary sharks, the nurse shark only eats approximately 1% of their body weight per day (Skomal, 2016). When feeding, nurse sharks use their highly flexible bodies to wiggle and twist themselves into small reef crevices in order to trap and consume their prey. In fact nurse sharks are so flexible that they are able to bite their own tails (Skomal, 2016).
Their flexibility isn’t the only advantage nurse sharks have when it comes to feeding on hard shelled crustaceans. Nurse sharks have been observed rolling their pectoral fins under their bodies while laying under a reef ledge. It is thought nurse sharks mimic a reef crevice, offering small reef fishes and invertebrates a “safe” haven (Tricas, et al., 1997). The nurse shark also possesses a pair of barbels around the mouth. They function as additional sensory organs for the nurse shark, helping the shark taste and feel their way around the sea floor (Tricas, et al., 1997; Parker, 2008). Possibly their best adaptation to benthic life is their teeth. Nurse sharks have plate-like teeth, which lay flat like pavement in the jaws. When a nurse shark has honed in on their prey, they are able to attack in a split second. They suck in a huge amount of water, along with their prey, in just a fraction of a second (Parker, 2008; Skomal, 2016). It is thought that the sucking sounds they make when feeding is how the nurse shark got its name, although it has also been suggested the name is from the Old English for sea floor, “Hurse” (Parker, 2008).
Nurse sharks have been extensively studied in zoos and aquariums, as they are one of the 40 shark species known to adapt well to life in human care (Parker, 2008). One thing nurse sharks have shown us is their great ability to learn. In fewer than 10 training sessions, nurse sharks came to associate certain sounds and movements with food (Parker, 2008). They also have the ability to discriminate shapes and colors, allowing aquarists to condition them to recognize their particular shape to receive food. They can even learn to navigate simple mazes as quickly as mice or rats (Parker, 2008).
Chris, M. (2013, April 1). Nurse shark training [Video Clip]. Retrieved from https://www.youtube.com/
The nurse shark is typically a very relaxed shark. They are frequent visitors to shark diving spots, and are known to respond well to touch. However, like anything with a mouth, they have the ability to bite people. Although they have rarely been implicated in unprovoked attacks, unfortunate encounters with humans often means a death sentence for the nurse shark. Due to the nature of their bite, those that have been bitten by a nurse shark often are taken to the hospital with the shark still attached! So leave a resting shark lie!
TomoNews US. (2016, May 16). Shark attack: Nurse shark bites Florida woman on the arm and refuses to let go [Video Clip]. Retrieved from https://www.youtube.com/
Authority: Bonnaterre, 1788
Family: Ginglymostomatidae; 3 species
Length: Maximum of 10.5 ft (3.2 m)
Weight: 240 lbs (109 kg)
Habitat: Continental and island shelves, coral reefs, lagoons, mangroves, sandy flats and sea grass beds
Depth: 3 to 40 ft (0.9 to 12 m)
Gestation: 6 months
Litter Range: 20 – 30 pups
Home Range: Tropics and subtropics in eastern Pacific and Atlantic
Diet: Bottom and reef bony fishes, invertebrates, occasional sting ray
IUCN Status: Data Deficient; population assessments are lacking; occasionally taken in recreational and commercial fisheries
(Rosa, Castro, Furtado, Monzini, & Grubbs, 2006; Parker, 2008; Skomal, 2016)
Thanks for checking out one of my favorite sharks this week! If you missed last week’s Featured Species, be sure to check out the Greenland Shark. Leave me a comment and let me know what species you’d love to learn more about!
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
Nurse shark in the sand [Digital Image]. (2014 December 8). Retrieved from http://www.epicdiving.com/
Parker, S. (2008). The encyclopedia of sharks (2nd ed.). Buffalo, NY: Firefly Books Ltd.
Rosa, R.S., Castro, A.L.F., Furtado, M., Monzini, J. & Grubbs, R.D. 2006. Ginglymostoma cirratum. The IUCN Red List of Threatened Species 2006: e.T60223A12325895.
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.