Plague! The word conjures images of horrors past, piles of festering medieval dead overrun by rats. It’s not a disease of the past though; the bacteria that causes plague can be found in the United States, and a few cases of human bubonic plague happen every year.

The animals that carry plague in the US are mostly rodents—rats, ground squirrels, and prairie dogs—and their fleas can pass plague bacteria to humans if they decide to bite us. Good news, though: The adorable little owls that live in burrows alongside those plaguey rodents seem to be immune. Although the owls have fleas capable of carrying plague, they are not infected—and their immunity could provide some interesting information to scientists studying the disease.

A Pile of Poo on Every Doorstep

Western burrowing owls (Athene cunicularia) nest underground, often re-using rodent burrows. Working with these predatory birds is not for the faint of heart; even small owls have powerful beaks and claws. Burrowing owls live in areas where you are just as likely to stick your hand in a burrow and and pull out a rattlesnake as an extremely irate little raptor.

Dr. Jim Belthoff of Boise State University has spent years sticking his arm into nest tunnels in search of owls—often past piles of excrement. In addition to being very cute and fluffy, these owls have an endearing habit of decorating their nests with turds. Not their turds, mind you; they collect and bring mammal dung back to their front doorstep. It’s thought the poo attracts insects that the owls snack on.

Adding to the grossness, Belthoff noticed burrowing owls seemed to have lots of fleas. “We considered the fleas a nuisance, as they would jump on us as we captured and banded the owls, and they would infest our field vehicles.” This made him wonder: Do the fleas affect the owls? And what kind of fleas were they?

The researchers knew burrowing owls used prairie dog and ground squirrel burrows in many portions of their range. Both those rodents host fleas that can carry the plague bacteria Yersinia pestis, maintaining the plague in a cycle of mutual infestation. (Humans play into that cycle, too, when they’re bitten by fleas that have abandoned a rodent corpse in search of food.) So Belthoff assembled a team of ecologists, entomologists, microbiologists, public health professionals, and volunteers to investigate how owls, fleas, and plague interacted with that rodent system.