shark, the silvertip shark sometimes perform a stereotypical threat display if pursued by divers, warning that it is prepared to attack. The display begins with the shark accelerating away to a distance of , before turning and charging towards the perceived threat. At a distance of two body lengths, the shark brakes, turns broadside, drops its pectoral fins, gapes its jaws, lowers the posterior two-thirds of its body, and "shivers". The last two elements of this display are unique to this species; the "shivering" may serve to emphasize its white fin markings. If the diver persists, the shark may rapidly close in and slash with its upper teeth. Feeding The diet of the silvertip shark consists primarily of bony fishes, such as grouper, mackerel, tuna, escolars, lanternfish, flyingfish, wrasses, and soles. Eagle rays, smaller sharks, and octopus are occasionally taken. Larger sharks tend to be more sluggish and take more benthic prey. The differently shaped dentition in their upper and lower jaws allows them to tackle large prey, gripping and sawing off chunks of flesh with violent twists and turns. Silvertip sharks have been observed swimming around the periphery of groups of feeding sharks of other species, occasionally dashing in to steal food. This species often approaches ships, as they are attracted to certain artificial, low-frequency sounds. Life history Like other requiem sharks, the silvertip shark is viviparous; once the embryos exhaust their supply of yolk, the depleted yolk sac develops into a placental connection through which the mother delivers nourishment. In the Southern Hemisphere, mating and parturition both occur in summer. Courtship involves the male biting the female to hold her for copulation; one female observed had the tip of her first dorsal fin bitten off from such activity. Females bear litters of one to 11 (usually five or six) young after a gestation period of about one year, on a biennial cycle. The newborns have been reported to measure and long by different authors, and are found in shallower water than adults. The growth rate is highly variable in the wild: Kato and Hernandez (1967) reported juvenile silvertip sharks grow an average of , or 5.3% of their body length, per year, with some individuals growing as much as , 30.1% of their body length) per year and others showing negative "growth". Males have been reported to be sexually mature at or long, and females at long. Human