Scientists Discover Remains of Antarctic Elephant Seal in Indiana River

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In 1965, during a building excavation along the banks of the Wabash River near Lafayette, Indiana, construction workers discovered a curious jawbone buried in the mud. The find soon found its way to the Field Museum of Natural History in Chicago, where it was carbon dated and catalogued, but not identified.

Re-examining the 1,260-year-old jawbone decades later, a trio of scientists associated with the Smithsonian Institution and Queen Mary University of London determined the deceased owner, and they were quite surprised. It turns out the jawbone is that of a male Southern elephant seal.

The researchers recently detailed their discovery in the journal PeerJ.

Southern elephant seals are husky and hearty creatures, capable of diving to depths of a thousand meters and foraging over ranges of 10,000 kilometers, particularly impressive feats considering their bulky frames. Females tip the scales at up to 2,000 pounds while males can reach 8,800, more than six times heavier than a polar bear. 

Elephant seals' range circles the globe in the lower latitudes around Antarctica, but they've been known to very rarely travel as far north as Baja California. This elephant seal, however, seemed intent on going where no southern elephant seal had gone before (at least to our knowledge).

Map showing the extant elephant seals distribution ranges in the Americas and adjacent areas and detail of the geographic location where the jawbone was found.

The male elephant seal "was an errant migrant that swam northward from the South American coast into the Mississippi River system via the Gulf of Mexico, and eventually stranded upriver in Indiana where [he] was killed or scavenged by Indigenous people," the researchers described.

They noted that the seal would have been swimming the river during the time that America's Mississippian culture inhabited an area extending from northern Florida to Illinois. Intentional cuts on the jawbone indicate some amount of human tampering, perhaps by Mississippians.

"Another, and less likely explanation, is that the skull was collected by Indigenous peoples along the coast of South America or at an intermediate point (including the Mississippi drainage or coastal Americas), and then transported (singularly in one lifetime, or across a trade route) until its deposition on the banks of the Wabash River," the researchers note.

They also acknowledge that the jawbone could have belonged to a northern elephant seal, which would also have had to make an impressive journey to reach Indiana, traveling from the Northern coast of California "along the northernmost border of North America through the Arctic reaching the North Atlantic Ocean, to finally enter into a river system via the Gulf of St. Lawrence or the Gulf of Mexico."

To the scientists, the find suggests "that invasions of freshwater systems by marine mammals have happened frequently through time."

Source: Valenzuela-Toro AM, Zicos MH, Pyenson ND. 2020. Extreme dispersal or human-transport? The enigmatic case of an extralimital freshwater occurrence of a Southern elephant seal from Indiana. PeerJ 8:e9665

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