The only remaining evidence of the Scioto madtom’s existence floats in jars of ethanol tucked in the bowels of a squat warehouse in Ohio. Extracted from its jar, a madtom carcass, with its pale flesh and dull bluish eyes, looks more like a pinky-sized ghost than a venomous, bottom-feeding catfish.

 

The International Union for Conservation of Nature, which organizes the international species lists, declared the Scioto madtom extinct in 2013. It had last been seen alive in 1957. But the United States still classifies the catfish as endangered, despite the U.S. Fish and Wildlife Service—the federal organization in charge of the endangered species list—agreeing that the fish is gone. Without clear incentive to delist the Scioto madtom, yet also without proof that there are any left to save, the catfish has drifted into extinction purgatory.

 

It might seem simple to determine when a species has gone extinct, but declaring it is trickier than expected. Researchers can’t prove that an animal no longer exists by simply not finding it when they go out looking for it. Often biologists rely on models of population trends based on extensive surveys—which are done as funding permits, not as needed—but a recent paper in the journal BioScience supports longstanding concerns that these surveys don’t always match real population trends. Biologists believe dozens of species should be declared extinct, yet remain on the endangered list. Concerns about protecting habitat and troubles determining whether these species are really, truly extinct keep these critters in a kind of limbo.

 

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