Natural History Notes on Tiger Sharks, Galeocerdo tigrinus, Caught at Key West, Florida, with Emphasis on Food and Feeding Habits

T HE genus Galeocerdo belongs to the great family Carchariidae, the gray sharks. A number of species have been attributed to this genus, but the present tendency is to reduce these names to synonymy and make the genus monotypic-Galeocerdo arcticus. However, in this article the names used by the authors quoted will for convenience be retained. SIZE ATTAINED.-The tiger shark is one of the largest of the sharks that inhabit our coastal waters. It is said to attain a length of 20 to 30 feet. This may be true, but in this search no record of such giants has come to light. I cannot find anyone who has one as long as even 20 My own largest 11 ft., 6 in. Stewart Springer writes (personal communication) that in Florida waters he has measured many over 12 ft., one over 13 and none over 14 ft. He says that his fishermen friends have spoken of specimens over 16 and 18 feet long, but none of them had actually these giants. A specimen of G. tigrinus 15 ft., 2 in. long, reported by Burton (1941), was caught off the Charleston (South Carolina) jetties in 1940. This big male is the largest tiger shark known to have been captured in Western Atlantic or in Gulf-Caribbean waters. Beebe and Tee-Van (1941) say of the tiger shark in the eastern Tropical Pacific-Reaches a length of at least 20 ft. But the three largest specimens they were 10 ft., 1 in., weight 366 lbs.; 10 ft., 6 in., 505 lbs., and 12 ft., 9 in., 780 lbs. However, Whitley in his Fishes of AustraliaPart I, Sharks (1940), records as Galeocerdo rayneri an individual taken in 1936 at Maroubra, New South Wales, which 15 ft., 6 in. This is the largest tiger shark taken in any ocean, of which record has been found in this search. PHYSICAL CHARACTERS.-The tiger shark is well named-for its physical appearance and for its habits. It is a large, heavy shark, and its bluish-gray sides are marked with dark vertical bars or stripes like a tiger, as is faintly shown in Plate I. Sometimes the sides have short bars and these are often set staggered, whence probably comes the West Indian name leopard shark. From the figure it may be noted that Galeocerdo is very heavily built forward of dorsal fin I. It has a large bluntly rounded head, wider than deep, with wide heavy jaws having a large vertical gape. Both jaws are beset with many large, serrate, sickle-shaped or notched teeth-the hooks on the teeth all pointing outward right and left (Fig. 2). No explanation has been found for the peculiar shape of the teeth, but I suggest that they function with a shearing bite. These large jaws and saw-edged teeth are plainly adapted for chopping the prey into large fragments, which are swallowed whole. Of sharks whose teeth are known to me, only Carcharodon, the great white shark, has better chopping teeth. HABITS.-In its habits the tiger shark lives up to its name, being fearless,