The nurse shark was first described by Bonnaterre (1788), as Squalus cirratus. The current scientific
combination, Ginglymostoma cirratum was first assigned by Muller and Henle in 1841.
Gynglymostoma is derived from the Greek words "gynglimos" = hinge and "stoma" = mouth.
The species name cirratum is translated from Latin as curl. Synonyms used to refer to
this species in past scientific literature are Squalus punctulatus Lacepède 1800, Squalus
punctatus Bloch & Schneider 1801, Squalus argus Bancroft 1832, Ginglymostoma fulvum
Poey 1861, and Ginglymostoma caboverdianus Capello 1867.
Similarities in the reproductive cycle may indicate a close relationship between the nurse shark family
Ginglymostomatidae and the whale shark family Rhincodontidae. Members of the order Orectolobiformes probably
are most closely related to the mackerel sharks of the Order Lamniformes.
The term "nurse" probably is derived from "Nusse", the common name originally applied to catsharks of the family
Scyliorhinidae, to which G.cirratum then was thought to belong. In Caribbean waters, the nurse shark is still often
referred as "tiburon gato" or cat-shark.
Other common names used to refer to this shark include amerika-tenjikuzame (Japanese), ammenhai (German),
atlantinpartahai (Finnish), atlantischer ammenhai (German), bañay (Spanish), barroso (Portguese), buux (Wolof),
cação-lixa (Portuguese), carpet shark (English), cat shark (English), con barbillas (Spanish), dogfish (English),
dormedor (Portuguese), gata (Spanish), gata común (Spanish), gata manchada (Spanish), gata nodriza (Spanish),
gullamano (Spanish), kathaai (Dutch), lambaru (Portuguese), lixa (Portuguese), nodriza (Spanish), peixe anjo
(Portuguese), pejebobo (Spanish), rekin wasaty (Polish), requin dormeur (French), requin nourrice (French),
sand shark (English), sartji (Sranan), squalo nutrice (Italian), tiburón de arena (Spanish), tiburón de barbillas
(Spanish), tiburón gata (Spanish), tribon di piedra (Spanish), tribon di santu (Spanish), tribon nocente(Spanish),
tubarao-ama (Portuguese), tubarao-dormedor (Portuguese), tubarão-enfermeira (Portuguese), tubarão-pajem (Portuguese),
vache de mer (French), verpleegsterhaai (Dutch), and zandhaai (Dutch).
Common in the Atlantic and in the eastern Pacific, in coastal tropical and sub-tropical waters. Reported from
Senegal to Gabon, Rhode Island to Southern Brazil, and Mexico to Peru. Also, some individuals have been
reported in the Gulf of Gascogne in southwest France. This species is locally very common in shallow waters
throughout the West Indies, south Florida and the Florida Keys. Apart of the eastern Pacific, the nurse shark
is absent from the Indo-Pacific area, where other related groups have successfully evolved.
World distribution map for the nurse shark
The nurse shark is a nocturnal animal that rests on sandy bottoms or in caves or crevices in rock in shallow waters
during the day. They occasionally occur in groups of up to 40 individual, as they lie very close together sometimes
even piling upon one another.
Nurse sharks are very active during the night. In addition to swimming near the bottom or well off it,
the nurse shark can clamber on the sea floor, using its flexible, muscular pectoral fins as limbs. Large
juveniles and adults are usually found around deeper reefs and rocky areas at depths of 3-75 meters (10-250 ft)
during the daytime and migrate into shallower waters of less than 20 meters (70 ft) deep after darkness.
Juveniles up to 170 cm (6 ft) are generally found around shallow coral reefs, grass flats or mangrove
islands in 1-4 meters (3-13 ft) of water. They often lie in groups within limestone solution holes or
under rock ledges.
Nurse sharks show a strong preference for certain resting sites, and repeatedly return to the same
caves and crevices after a nocturnal activity.
- · Distinctive Features
Nurse sharks have two spineless, rounded dorsal fins with the first dorsal fin much larger than second,
and one anal fin. The origin of the first dorsal fin is about over the origin of the pelvic fin. The caudal
fin is more than ¼ of the total animal length.
FAO Species Catalogue (1984) vol. 4 part 1.
photo by George Burgess©
The sub-terminal mouth is placed well in front of the eyes, the spiracles are minute, and moderately
long barbels reach the mouth. Nasoral grooves are present, but there is no perinasal groove.
- · Coloration
Adult nurse sharks generally range from light yellowish tan to dark brown in color. Juveniles up to 60 cm (23 in)
have small black spots, with an area of lighter pigmentation surrounding each spot, covering the entire body. These are
bands of lighter and darker pigmentation along the dorsal surface.
Juveniles (70-120 cm / 28-48 in) are capable of limited color changes. In a tank experiment small nurse sharks,
covered for just a few minutes became considerably lighter than individuals exposed to full sunlight.
Unusually pigmented individuals (e.g. brilliant yellow or milky white) have been reported several times.
Nurse shark showing color pattern, photo by George Burgess©
FAO Species Catalogue (1984) vol. 4 part 1.
Nurse sharks possess independent dentition, the simplest type of tooth arrangement found in sharks.
This means that there is no overlap between teeth, and that forward movements of teeth leading to
shedding does not depend on other teeth. In sharks with various degree of overlapping dentition,
replacement of teeth cannot take place until outer blocking teeth are lost. Replacement rates among
juveniles are generally faster than for adults. Also teeth replacing occur faster in summer, when water
temperatures are higher.
- ·Size, Age, and Growth
Averaging 220-270 cm (7.5-9 ft) in total length and weighing 75-105 kg (167-233 lbs), adult females
reach a larger size than adult males (210-260 cm / 7-8.5 ft ; 90-120 kg / 200-267 lbs). Size at maturity is
also larger for females, about 225 cm (7.5 ft) in females vs 210 cm (7 ft) for males. Size at birth is in the
28-30 cm (11-12 in) range, with growth rates for juveniles of about 13 cm (5 in) and 2.3 kg (5 lbs) per year.
Once maturity is reached, growth rates are usually much lower.
Nurse sharks feed on fish including
© David Snyder
- · Food Habits
A nocturnal predator, the nurse shark feeds mainly on fish especially stingrays, molluscs (octopi, squids and clams)
and crustaceans. Algae and corals are occasionally founded in the stomachs as well. The nurse shark has small
mouth, but its large, bellows-like pharynx allows it to suck in food items at high speed. This system probably
allows the species to prey on small fish that are resting at night, species that are too active for the sluggish
nurse shark to catch during the day. Heavy-shelled conches are flipped over, and the snail extracted by use of
suction and teeth.
Young nurse sharks have been observed resting with their snouts pointed upwards and their bodies supported off
the bottom on their pectoral fins. Some suggest this posture may possibly provide a false shelter for crabs and
small fishes that the shark ambushes and eats.
- · Reproduction
Egg cases from nurse shark, photo by George Burgess©
The nurse shark is an ovoviviparous species. This means that embryonic development occurs in an egg case within
the mother's ovary. The embryo has its own yolk sac, which is absorbed during development, and there is no placental
nourishment from the mother. The nurse shark has a biennial reproductive cycle. After mating, gestation takes about
six months. The young are born in late spring/early summer with litter of 20-30 pups. Each pup measures 10.6-11.8 inches (27-30 cm) total length. It then takes another eighteen months for the ovaries to produce mature eggs for the next breeding. In the waters of the Florida Keys and
the Dry Tortugas archipelagos, the reproductive behavior of the nurse shark has been regularly observed and studied,
making it's copulatory behavior among the best known in shark species.
Males approach females that resting on the sea floor or are swimming just above it. The male then bites one
of the female's pectoral fins simultaneously pushing, trying to turn her onto one side. In this position it
is easier for a male to insert his clasper, vigorously bending the lower portion of his body towards the female's cloaca.
A large number of males generally try to mate with a single female, often leading to females bearing
numerous scars and bruises from male bites. Females frequently try to avoid contact with males by swimming in
very shallow water, where they can bury their pectoral fins in the sand.
A lemon shark with two bull sharks in background - all predators of the nurse shark
© Klaus Jost
- · Predators
There are no species that regularly prey on nurse sharks. However some larger sharks are known
to feed occasionally on them. Remains of nurse sharks have been found in lemon shark and tiger shark
stomachs, and attacks on nurse sharks by bull sharks and great hammerhead sharks have been observed.
- · Parasites
Nematodes have been observed in the gills of nurse sharks in captivity at
the New York Aquarium, U.S.
Nurse shark remains have been found in the stomachs of the tiger shark
Importance to Humans
At present there is not a fishery for this species. The fins are not marketed and the meat, although edible,
is not often retained for human consumption. However it is sometimes sold as crab bait.
Nevertheless, nurse shark are caught and killed by fishermen in some regions because they
are considered a nuisance animal that takes bait intended for other species. In the Lesser Antilles,
where it often raids fish traps, it is considered a pest. Commercial fishers in the United States routinely
release nurse sharks alive.
In the past nurse sharks were sought for various reasons. The liver oil often was used as fuel. The oil also
was used by commercial sponge fishers to calm the water surface, allowing them to more readily locate sponges
on the seafloor. The skin was considered the best of all elasmobranch species, being extremely tough and
thick, and was used to make high quality leather. The skin also was occasionally salted for human consumption.
Nurse shark caught on a rod and reel
Danger to Humans
Mainly non-aggressive, generally will swim away when approached. However, some unprovoked attacks on
swimmers and divers have been reported. If disturbed it may bite with a powerful vice-like grip capable
of inflicting serious injury. In some instances, jaws release was accomplished only after using surgical
instruments. The frequency of bites has increased recently as a result of ecotourism feeding operations.
Nurse shark up-close
Although the nurse shark is not an endangered species, its abundance in the littoral waters of
Florida has decreased in the past decades. The presence of this species in areas with constant
anthropogenic activity makes it susceptible to disturbance. Because of its relatively docile
behavior, swimming with (and handling and feeding) nurse sharks is a very popular form of ecotourism.
The effects of high levels of interactions with humans in coastal waters are not completely known,
but the fact that nursery areas are now limited only to remote regions suggests a correlation.
Identification and protection of these areas, coupled with further research on the biology of
nurse shark, is essential to provide effective conservation.
This shark is listed as "Data Deficient" with the World Conservation Union (IUCN). The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.