Thresher Sharks vs. Whales – Finding Melville’s Shark?

Back in the day (earlier this year) Andrew at Southern Fried Science had a series of posts called “Finding Melville’s Whale,” in which he poetically summarized chapters of the Herman Melville classic (and required reading for anyone serious about the salty life) Moby Dick.  These were apparently not that popular with the readership and eventually discontinued (though I personally enjoyed them), but one entry in particular piqued my interest.  In chapter 32, Melville describes the various whale species encountered by whalers and mariners of the day.  Most of the entries are recognizable, and a few are multiple descriptions of the same species (Andrew has his take on what they all likely are in the first comment), but one stood out in particular; the “thresher.”  Andrew guessed that this was probably a reference to orcas, but José Castro’s excellent book The Sharks of North America (my review here) shed some new light on the subject.  It looks like one of Melville’s whales may have actually been a shark.

Here is Andrew’s verse on the “thresher whale,” adapted from Melville’s description:

OCTAVO, Chapter 5, Thresher
A flogger of beasts,
the leviathans’ task-master.

In Melville’s sizing scheme, whales are classified as Folios, Octavos, and Duodecimoes.  Folios are the largest whales, Octavos are the mid-sized (usually toothed) species like orcas and pilot whales, and Duodecimoes are the small cetaceans like dolphins and porpoises.  The thresher “whale” is classified as an Octavo, and specific mention is made of its ability to “flog” its prey.  Andrew likely took this to symbolize the behavior of a pod of orcas cooperatively attacking a large whale.  However, given the relative accuracy of the other descriptions, I don’t think Melville would have used such a specific visual if the animal didn’t match it.  The long, whip-like tail of the thresher shark (Alopias vulpinus) is certainly used for the flogging of small fish, and Castro mentions credible size estimates that place the thresher at a maximum length of 20-25 feet.  This is within the size range of other Octavo species like narwhals and false killer whales (keep in mind that about half of that is tail).  All that said, where does the idea of thresher sharks attacking whales come from?

Whale flogger? Image from newenglandsharks.com

According to Castro’s entry, descriptions of thresher sharks whacking whales in the head are as old as the art of seafaring, and persist until the late 1930s despite a lack of any kind of evidence.  He cites a bizarre account by sir Richard Hawkins from 1622 of thresher sharks working together with swordfish to bring down whales; the sharks would whip the whale from above and the sides until it would dive, at which point the waiting swordfish would stab it in the gut with their rostrums.  Perley’s 1852 description of the fauna of the Gulf of Saint Lawrence also includes a description of a thresher shark attack on a whale, and even posits that breaching behavior results from the mammal’s attempt to escape or drive off its selachian tormentor.

It’s unclear where the assumption that thresher sharks slap whales around on a regular basis originated, but it was accepted as fact at the time Herman Melville was writing Moby Dick.  It’s possible that Melville, upon hearing descriptions of the thresher shark’s size and behavior, classified it as a type of whale, though other Octavo-sized sharks like the great white were known at the time.  His description does fit both the physical description of the thresher shark and reflects then-common misconceptions about its behavior.  It seems as though a shark managed to sneak its way into the cetology of Moby Dick.

Source Cited

Castro, J.  2011.  Common Thresher.  Pages 241-247 in The Sharks of North America.  Oxford University Press, New York.


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