Azhalia Pottinger

Running from Blue Cypress Lake to the Atlantic Ocean, the St. Johns River takes on many forms. In quiet marshlands, broad winding waterways, cypress-lined floors and tidal estuaries, the river reshapes itself again and again. The 310-mile river creates bountiful fishing for boaters, soothes the fiercest storm surges and provides a home for countless species from manatees to bald eagles. In recent years though, it has also been forced to take an unwelcomed guest.

This Halloween, instead of looking to the sky for spooky critters, like the half-million bat colony around the University of Florida, consider what's happening beneath your feet: a surprising number of mammals, from raccoons to otters, roam underground in stormwater drains. "There's interstates below your feet," says UF's Alan Ivory, a PhD student in wildlife ecology. While studying animals in UF's ponds, Ivory noticed an otter scurrying into a storm drain.