The capybara is the largest member of the rodent family. Abundant over much of northern and central South America, this plump, pig-sized cousin of the sewer rat spends much of its time in the water, foraging for food (mostly aquatic grasses) and protecting itself from predators like jaguars in wetland areas and semi-flooded savannahs. Its webbed feet and easy-dry fur make its semi-aquatic life easier to manage, and it is still possible to encounter herds of up to 40 capybaras in many South American countries. They’ve even showed up as an invasive species in Florida’s endless wetlands.

When Jesuit missionaries arrived in South America in the 16th century, they found that in some places the locals ate capybara the way Americans eat beef. And so what if it was essentially a huge hamster? The ancient Romans loved nothing more than a baked mouse, and until the 20th century the rabbits Europeans ate on the regular were considered part of the rodent family. But the Jesuit missionaries couldn’t eat capybara during Lent or on other abstinence days—and they were in the awkward position of telling new converts that the capybara was no longer kosher as well.

What to do? As the legend goes, you write to Rome and ask for clarification: “There is a strange animal here, unseen in Europe and resistant to easy classification. It has webbed feet and lives in water, and has a fishy flavor. It’s a fish, right? The newly-baptized locals enjoy this aquatic delight, by the way.”

Rome responded to the Jesuit missionaries in the affirmative: The strange creature that tasted like fish and lived in the water and had webbed feet was indeed to be classified as a fish. From that day on, everyone enjoyed supping on this mighty mouse in a state of grace. Even today, Venezuelans have a custom in Lent of eating capybara, that most jesuitical of all the fishes.

James T. Keane, Senior Editor at America.