<I>Ginglymostoma Cirratum</I>
BULLETIN OF MARINE SCIENCE, 60(3): 1015-1016, 1997
CLOSE ENCOUNTERS WITH THE NURSE SHARK, GINGLYMOSTOMA CIRRATUM
Donald R. Moore
ABSTRACT During the late 1940s, the writer experimented with the behavior of the nurse shark, Gin- glymostoma cirrawm (Bonnaterre, 1788), This was done around the inshore reef at Palm Beach, Florida. Large nurse sharks would simply swim away when bothered; younger indi- viduals would bite if not released promptly.
The beaches and shallow water environment of the east coast of Florida are dominated by quartz sand. This sand is moved south by strong wave action and current during winter storms. During the warmer months, however, the wave action is usually gentle or nonexistent, and the water very clear. A rock reef is usually found offshore, but most of the corals are a few scattered small hardy species. The reef is about 300 m from shore at the terminus of Worth Avenue in Palm Beach. The reef is composed of Pleistocene limestone, and projects 1 to 2 m above the surrounding sand. Along the inner edge of the reef, the rock is often undercut and forms shallow caves, a favorite haunt of nurse sharks, Ginglymos- toma cirratum (Bonnaterre, 1788). The nurse shark is a common medium-sized shark living in shallow marine waters. Its range includes the warmer waters from the southeastern United States to the coast of Brazil. In Florida, nurse sharks are common in the Florida Keys, Florida Bay and up the east coast at least as far as Cape Canaveral, and range to the Carolinas during the summer. Individuals 2 to 3 m long are common, large ones range up to about 3.5 m while the maximum is around 4.3 m (Bigelow and Schroeder, 1948). From 1946 through 1949, I worked as beach lifeguard for Lido Pools just south of Worth Avenue and the fishing pier. I had many opportunities to swim out to the reef in quiet weather and did so. During pleasant weather and clear water, I observed many nurse sharks underneath ledges or lying near the reef on sand bottom. At first I just watched the sharks and was universally ignored. Nurse sharks at that time were considered to be harmless by most people, so I decided to experimeqt with shark behavior. I would find a large shark with its head and much of its body underneath a ledge. I would then dive down beside the shark's tail fin, plant my feet on the bottom, seize the shark's tail, and pull. There would be a commotion, but somewhat on the sluggish side. The shark would emerge and slowly swim away. I always picked the largest sharks and never had a problem with any of them. I then tried riding those individuals lying in the open. I would dive down, take hold of the pectoral fins and hunch down on the shark's back. The shark would begin to swim and would slowly build up speed. Although their skin is rough, all the denticles point aft, and so I would simply slide off as speed increased. All of this took place in water no more than 6 m deep. A young man (name lost over time) hearing of my research, decided to try it also. He grabbed the tail fin of a young shark about 1.5-m long. It promptly turned and bit him on the thigh. There was not much physical damage, but this person gave up his shark study.
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A documented case of nurse shark bite is found in Sea Pests by C. Phillips and W. H. Brady (1953). In July, 1950, a student at the University of Miami Marine Laboratory, Warren Rathjen, was bending over in about a meter of water. He was wearing rather loose swim trunks, and the succulent white meat just above his tanned leg was exposed. A small shark tried taking a bite out of the exposed portion. Rathjen seized the shark by the tail fin and threw it away. Since the shark was not carefully examined, Phillips and Brady, op. cit., maintain that it cannot be identified. However, it was a nurse shark (Rathjen, personal communication). I have seen or heard of a number of accounts of nurse shark attacks on humans over the last four decades. Almost invariably, this was the result of the human bothering the shark. Usually these stories appear in newspapers or sports maga- zines. The most recent of these events that I have seen was in the Miami Herald for 25 January 1996. "Jaws in reverse: He attacks shark." "A shark was attacked in the keys (sic) by a tourist from Kansas City." "The visitor was in thigh deep water Thesday when he spotted a 3-foot long nurse shark." 'He grabbed it by the tail and didn't let go,' said Bob Bodner, assistant manager at Bahia State Park. 'And it turned around and bit him on the leg.' His leg wrapped in a towel, tourist Christopher Riley, 33, was taken to Fisherman's Hospital in Marathon for treatment. 'As he said, 'I was being a stupid tourist', Bodner said." Nurse sharks are large, tough stupid creatures. In retrospect, swimming out some distance from shore alone to disturb large animals armed with teeth was a very poor idea. At the very least, one should have a companion along to come to the rescue, or to report the reason for one's disappearance.
LITERATURE CITED
Bigelow. H.B. and W.e. Schroeder. 1948. Fishes of the western North Atlantic: Part 1. Sharks: Pages 59-576 in Mem. Sears Fdn. Mar. Res. (1): 576 p. Miami Herald, 25 January 1996. Phillips, e. and W. H. Brady. 1953. Sea pests. The Marine Laboratory, University of Miami: 1-78.
DATE ACCEPTED: June 26. 1996.
ADDRESS: Division of Marine Geology and Geophysics. Rosenstiel School of Marine and Atmospheric Science. University of Miami. 4600 Rickenbacker Causeway. Miami. Florida 33149-1098.