An analysis of shark-tooth weapons from the 19th century reveals two shark species, the spot-tail and dusky, where once common in the Gilbert Island reefs in the Central Pacific. The sharks are no longer found in the area.
Ironically, the dusky shark grows to about the same size as the biggest weapon measured in the study, which is published in PLoS ONE. That 15-foot-long sword was created by Gilbert Island men and was studded with sharp shark teeth.
"There was an amazing array of weapons, from shark tooth brass knuckles to lances that were about 15 feet long," lead author Joshua Drew told Discovery News. "We don't know exactly when they were first made, but we know that when the first Western people wrote about the Gilbert Islanders in the 1840s, they remarked about their weaponry."
Drew is a conservation biologist at Columbia University. He and colleagues Christopher Philipp and Mark Westneat analyzed 122 such weapons and related items, all housed at the Field Museum of Natural History in Chicago.
High-resolution photographs of the teeth, matched with known shark data, determined that eight species were hunted for the weapons. The spot-tail and dusky sharks were part of that group, but these species have never before been reported from Gilbert Island reef waters.
The discovery suggests that these two sharks were hunted by the islanders until they were locally extinct.
Historical records explain how these sharks and the others were hunted. The process involved a strict set of procedures. First, two men would go out in a narrow outrigger canoe measuring 10 to 15 feet long.
"One would use a series of coconut shells as a rattle to lure the shark close," Drew explained. "When the shark would come to take an investigatory bite, he would thrust a stick down the shark's mouth, forcing the jaws open. At the same time, the other man would slide a rope around the tail of the shark."
At that point, the immobilized shark would be fastened to the side of the canoe, hauled ashore and then killed. Its meat was consumed, with the sharkskin later used to craft household goods. The skin and the teeth were used to construct weapons.
Records of early missionaries describe how the weapons were used in intertribal warfare.
"Two main combatants would have a duel using swords and dressed in armor made of tightly woven coconut cord and helmets of dried pufferfish," Drew said. "They would be joined by several assistants who would use the long lances to try to reach over their own combatant and attack his foe."
"These thrusts would, in turn, be parried by the other combatant's assistants," he added. "So while the two main men were fighting hand to hand, there was this sort of aerial combat overhead with the 10 to 15-foot lances."
While the shark teeth could clearly do some serious damage to humans, they were not enough of a defense to prevent them from overfishing.
Julia Baum, a University of Victoria biologist, has extensively studied sharks. She told Discovery News, "Drew's creative study sheds new light on how we have impacted shark populations."
It is now hoped that attention to the important cultural connection that the Gilbert Islanders have to sharks will help to spark conservation efforts in the region.
Drew explained, "Kiribati, the country within which the Gilberts lie, is already one of the most progressive countries, and I think highlighting how their traditional culture can be tied to conservation will only help them continue to be at the head of the pack when it comes to marine conservation."