The big brown bat is a widespread and native Colorado bat. Open occurrence databases hold 1,341 records for it in Colorado, gathered largely from museum specimens and survey work rather than daytime photographs, which is what you would expect from an animal that flies only after dark.
Where and when to see big brown bats in Colorado
This is the bat most likely to share a building with people. It roosts in attics, barns, rock crevices, and tree cavities by day, then hunts beetles and other hard-shelled insects at dusk, often over water or open ground. The records tilt strongly toward the Front Range, with Boulder, Adams, Larimer, and Denver counties leading, and gather near reliable insect hatches such as Chatfield State Park and the South Platte River corridor.
A warm-season flier
Sightings climb through spring, spike in high summer when insect prey is thickest, then trail off toward winter. Big brown bats do not make a long migration out of Colorado; instead they wedge into cold-tolerant retreats and hibernate through the coldest months, so the near-empty winter record reflects sleeping bats rather than departed ones.
A bat built for beetles
Large and broad-muzzled for a Colorado bat, with glossy chocolate-brown fur and dark wings, the big brown bat is a heavy-jawed insect specialist that favors hard-bodied beetles. It is native and secure here, ranked S5 by NatureServe and least concern by the IUCN, and it remains one of the most familiar bats across the state’s towns and farmland.
Full species profile
