Common Thresher - Historical Perceptions

Historical Perceptions

The Greek philosopher Aristotle (384–322 BCE) wrote some of the earliest observations about the common thresher. In his Historia Animalia, he claimed that hooked threshers had a propensity for freeing themselves by biting through fishing lines, and that they protected their young by swallowing them. These "clever" behaviors, which have not been borne out by science, led the ancient Greeks to call it alopex (meaning "fox"), on which its modern scientific name is based.

An oft-repeated myth about the common thresher is that they cooperate with swordfish to attack whales. In one version of events, the thresher shark circles the whale and distracts it by beating the sea to a froth with its tail, thereby allowing the swordfish to impale it in a vulnerable spot with its rostrum. In an alternate account, the swordfish positions itself beneath the whale, while the thresher leaps out of the water and lands on top of the whale, hammering it onto the swordfish's rostrum. Yet other authors describe the thresher "cutting huge gashes" in the side of the whale with its tail. Neither threshers nor swordfish however are known to feed on whales or indeed possess the dentition to do so. The story may have arisen from mariners mistaking the tall dorsal fins of killer whales, which do attack large cetaceans, for thresher shark tails. Swordfish bills have also been found embedded in blue and fin whales (likely accidents due to the fast-moving fish's inertia), and thresher sharks do exhibit some of the aforementioned behaviors independent of whales.