Nurse sharks shrug off capture for science tags
Nurse sharks (Ginglymostoma cirratum) are bottom-dwelling sharks of warm coasts, rated vulnerable on the IUCN list. They cope with being caught, handled and tagged unusually well, which has made them a favourite subject for shark researchers who need an animal that recovers calmly once the instruments come off.
The genus name comes from Greek for hinged mouth and the species name from Latin for curled ringlets. Nobody is sure where nurse came from. One theory blames medieval spelling, when the n of an often migrated onto the next word, and old names for sharks included huss and hurse. Another, from a natural history of sharks, suggests an observer once saw a female give birth to live young and took it for nursing.
Adults are brownish with two rounded dorsal fins, a broad head and a long tail fin; the largest reliably measured reached 3.08 m, and older claims of 4.5 m and 330 kg are probably inflated. Newborns are spotted and about 30 cm long, and some individuals show piebaldism, a patchy loss of pigment. They range along tropical and subtropical coasts from Cape Verde to Gabon, from Rhode Island to southern Brazil, and from Baja California to Peru.
Juveniles keep to shallow reefs, seagrass and mangroves, while adults shelter under ledges by day, often resting in large groups, then forage alone at night over the seabed. They eat small fish including stingrays, plus crustaceans, molluscs, sea urchins and even algae, using suction that ranks among the strongest measured in any aquatic vertebrate; they may spit out and resuck food or shake their heads to break it up. Alligators and American crocodiles sometimes prey on them.
Unusually sedentary, they return to the same mating grounds year after year. Females breed every two years, mating in late June and July; after six months, litters of 21 to 29 fully formed pups are born, and one brood contained fourteen genotypes, evidence of several fathers. Status varies by region: least concern in the United States and Bahamas, near threatened in the western Atlantic.
Source: Nurse shark
