S. aureus can cause skin infections or, if it gets into the bloodstream, life-threatening illness. Most infections are easy to manage with penicillin and related antibiotics, but MRSA, the resistant variety, is on the rise; also known as a "superbug," it kills an estimated 18,000 Americans a year. In most cases, people contract the bacterium from a hospital stay. Hospitals are breeding grounds for antibiotic-resistant organisms, because patients are treated with a wide variety of antimicrobial drugs, prompting pathogens to develop defenses.

It's been clear for more than a decade, however, that people can catch MRSA strains outside of the hospital as well; researchers call these "community-associated" strains. For instance, pigs on livestock farms have been found harboring the bug, likely because farmers give antibiotics to food animals as they grow, another way of encouraging resistance to evolve. Other studies have found MRSA in pets and zoo animals; they may have been infected by human caretakers.

Now it appears that even animals in the wild can be infected with MRSA. Researchers led by epidemiologist Tara Smith of the University of Iowa's College of Public Health in Iowa City took samples from 114 animals that came into the Wildlife Care Clinic, which rehabilitates injured or orphaned animals, at Iowa State University in Ames. Seven of the animals, or 6.1%, carried S. aureus that was sensitive to methicillin; these included owls, pigeons, a beaver, a heron, and a squirrel. Three animals, or 2.6%, carried MRSA: two Eastern cottontail rabbits and a lesser yellowlegs, a migratory shorebird. (For comparison's sake: An estimated 1.5% of Americans carry MRSA in their noses.)