Overview
AT A GLANCE
- Common Name: Nurse Shark
- Scientific Name: Ginglymostoma cirratum
- Category: Fish
- Subcategory: Sharks & Rays
- Size: Total length: 7.5–9.8 ft (2.3–3.0 m); Maximum recorded: up to 14 ft (4.3 m)
- Weight: 165–280 lb (75–127 kg); large mature females can exceed 330 lb (150 kg)
- Lifespan: 25–35 years in the wild; up to 40 years in public aquariums
- Diet: Benthic carnivore / Suction feeder (spiny lobsters, crabs, stingrays, octopuses, squids, conchs, and sleeping reef teleost fishes)
- Habitat: Shallow inshore coastal waters, coral reefs, mangrove channels, sea grass beds, and submerged rocky ledges down to 250 feet (75 m)
- Range: Western and Eastern Atlantic Ocean, ranging from Rhode Island and the Gulf of Mexico down to southern Brazil, and coastal West Africa from Mauritania to Angola
- Conservation Status: Vulnerable (IUCN Red List)
The Nurse Shark (Ginglymostoma cirratum) is a heavy-bodied, bottom-dwelling coastal elasmobranch that ranks among the most common and culturally familiar shark species of the tropical Atlantic and Caribbean reef systems. Instantly recognized by its broad, flattened head, dual fleshy sensory barbels dangling from its upper lip, tiny eyes, and smooth, sandpaper-textured yellow-brown to grayish-tan skin, this tranquil-looking predator spends its daylight hours resting peacefully in social congregations beneath submerged limestone ledges and coral overhangs.
Unlike pelagic sharks like the blue shark or great white, which must swim continuously to generate water flow over their gills (obligate ram ventilators), Ginglymostoma cirratum possesses powerful pharyngeal muscles that enable buccal pumping, allowing it to rest completely motionless on the sea floor for hours. At dusk, the nurse shark transforms into an active, highly methodical nocturnal hunter, utilizing explosive suction forces generated by its muscular buccal cavity to vacuum armored crustaceans and reef prey directly out of impenetrable rock fissures.
Biology and Physical Characteristics
The feeding biomechanics of Ginglymostoma cirratum are arguably the most powerful of any marine vertebrate: by rapidly expanding its massive oral cavity while keeping its small, transverse mouth tightly constricted, it generates negative hydrostatic pressures capable of sucking Queen conch snails completely out of their thick shells within milliseconds. Its jaws are lined with multiple rows of small, fan-shaped, serrated crushing teeth adapted for pulverizing heavily calcified crab and lobster carapaces. Its pair of nasal barbels is densely packed with chemo-tactile sensory cells that detect buried prey beneath sand.
Behavior and Ecology
Nurse sharks display remarkable site fidelity, frequently returning to the exact same coral cavern or sand shelf year after year. They are surprisingly social during the day, frequently resting stacked upon one another in piles of up to twenty individuals. Mating involves an elaborate, physically intense courtship where males grasp the female’s broad pectoral fin with their teeth to stabilize her on the sea bed. The species is ovoviviparous, with females giving birth to litters of 20 to 40 fully formed, spotted pups after a six-month gestation.
Conservation and Human Impact
Ginglymostoma cirratum is listed as Vulnerable on the IUCN Red List. Due to its coastal inshore habitat preferences and docile diurnal nature, it is highly susceptible to coastal development, mangrove nursery clearance, coral reef loss, and direct recreational spearfishing. Although its meat is considered low-value, its tough dermal denticle hide was historically prized for high-grade leather, and it is frequently taken as bycatch in artisanal gillnet fisheries.
Interesting Factoid
The nurse shark has the strongest suction-feeding bite of any shark on Earth: it can expand its mouth cavity so rapidly that it generates a vacuum sound resembling a loud underwater gunshot, pulling snails and lobsters out of rocks in less than a second.