Grey reef shark
First shark known to perform a threat display.
The grey reef shark (Carcharhinus amblyrhynchos) is a requiem shark found throughout the Indo-Pacific, from South Africa to Easter Island. It is one of the most common sharks on coral reefs, typically seen in shallow water near reef drop-offs. This shark has a classic reef shark appearance: a broad, rounded snout and large eyes. It can be told apart from similar species by its plain or white-tipped first dorsal fin, dark tips on the other fins, a wide black band along the rear edge of the tail fin, and the absence of a ridge between its dorsal fins. Most individuals are under 1.88 meters (6.2 feet) long.
A fast and agile hunter, the grey reef shark mainly eats free-swimming bony fish and cephalopods. Despite its moderate size, its aggressive nature allows it to dominate many other shark species on the reef. These sharks often have a home range on a specific part of the reef and return to it regularly, but they are social rather than territorial. During the day, groups of five to 20 individuals gather near coral reef drop-offs, splitting up at night to hunt. Adult females also form groups in very shallow water, where the warmer temperatures may help speed up their own growth or that of their developing young. Like other requiem sharks, the grey reef shark is viviparous: the mother nourishes her embryos through a placental connection. Litters of one to six pups are born every other year.
This species was the first shark known to use a threat display—a stereotyped warning that it is about to attack. The display includes a hunched posture, lowered pectoral fins, and an exaggerated side-to-side swimming motion. Grey reef sharks often perform this display if followed or cornered by divers, signaling that they feel threatened. They have been responsible for several attacks on humans and should be treated with caution, especially if they begin to display. The species is caught in many fisheries and is vulnerable to local population declines because of its low reproduction rate and limited movement. Consequently, the International Union for Conservation of Nature lists it as endangered.
The grey reef shark was first described in 1856 by Dutch ichthyologist Pieter Bleeker, who named it *Carcharias (Prionodon) amblyrhynchos* in the journal *Natuurkundig Tijdschrift voor Nederlandsch-Indië*. Later authors moved it to the genus *Carcharhinus*.
Quick Facts
- Genus
- Carcharhinus
- Species
- amblyrhynchos
Facts from the source article.
Lore & Background
The grey reef shark was first described by Dutch ichthyologist Pieter Bleeker in 1856 as Carcharias (Prionodon) amblyrhynchos, based on a 1.5 m female from the Java Sea. It has the typical 'reef shark' shape with a broad, round snout and large eyes, and can be distinguished from similar species by the plain or white-tipped first dorsal fin, dark tips on other fins, a broad black rear margin on the tail fin, and the lack of a ridge between the dorsal fins. Its coloration is grey above, sometimes with a bronze sheen, and white below.
This species is found from South Africa to Easter Island, inhabiting shallow water near coral reef drop-offs. It is a fast-swimming, agile predator that feeds primarily on free-swimming bony fishes and cephalopods. Grey reef sharks are social rather than territorial, often forming groups of five to 20 individuals near drop-offs during the day, splitting up at night to hunt. Adult females form groups in very shallow water, where higher water temperature may accelerate growth. They are viviparous, with litters of one to six pups born every other year.
Reader's Guide
The grey reef shark is significant as the first shark species known to perform a threat display, a hunched posture with dropped pectoral fins and exaggerated side-to-side swimming, used when followed or cornered by divers. This species has been responsible for a number of attacks on humans and should be treated with caution, especially if it begins to display. It has been caught in many fisheries and is susceptible to local population depletion due to its low reproduction rate and limited dispersal, leading the International Union for Conservation of Nature to assess it as endangered. Along with the blacktip reef shark and whitetip reef shark, it is one of the three most common sharks inhabiting Indo-Pacific reefs, and actively expels most other shark species from favored habitats. Its consumptive influence on reef fish communities varies depending on whether sharks forage within the reef or on pelagic resources. Fossil teeth from the Late Miocene of Brunei represent the oldest known record of the species.
Did You Know?
- It can be distinguished by the broad, black rear margin on its tail fin and the lack of a ridge between the dorsal fins.
- Hunting groups of up to 700 grey reef sharks have been observed at Fakarava atoll in French Polynesia.
- Fossil teeth of the grey reef shark are known from the Late Miocene of Brunei.
More in Reef Sharks and Rays 1-24
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