Bats in Connecticut: Where to Look and What Signs to Watch For

Yes, bats are still common in Connecticut, but which bats are common has shifted. The big brown bat is now the species you are most likely to see, because it roosts in buildings and tolerates cold better than cave bats. The little brown bat was once the most abundant bat in the state, but its population fell by more than 90 percent after white-nose syndrome arrived around 2008, so sightings are now far rarer than they used to be. You can still find bats across the whole state, with the highest activity in the western highlands and along the Connecticut River valley where water and insects are plentiful. Nine species have been documented in Connecticut over the years, though several are migratory tree bats that only pass through seasonally.

Connecticut is home to nine recorded bat species, which fall into two groups. The first group is the cave and building bats that hibernate here through winter. These include the big brown bat (the most common today), the little brown bat (heavily reduced by white-nose syndrome), the northern long-eared bat (federally endangered), the tricolored bat (also hit hard by disease and proposed for federal listing), the eastern small-footed bat, and the Indiana bat (federally endangered and very rare). The second group is the migratory tree bats that spend summers in Connecticut and fly south for winter. These include the eastern red bat, the hoary bat (the largest bat in the state), and the silver-haired bat. The big brown bat, little brown bat, eastern red bat, and hoary bat are the four you are most likely to notice. For a closer look at bat biology, see our bat page.

The best places to spot bats are near water such as lakes, ponds, rivers, and slow streams, where insects gather at dusk. Forest edges, open meadows, and the gaps over fields are also reliable. Look for old barns, bridges, covered structures, and attics where building roosts may form. Good public spots include Sleeping Giant State Park, Pachaug State Forest, and the White Memorial Conservation Center in Litchfield, which has open water and mixed forest that bats favor. The western highlands of Litchfield County and the Connecticut River valley both hold strong bat activity. Migratory tree bats like the red and hoary bat are more likely seen high over the canopy or during fall migration along the coast. For more on Connecticut's wildlife areas, see the state hub.

Bats are nocturnal and most active from dusk to dawn. The best window to watch is the first hour after sunset, when they leave roosts to feed. In Connecticut, bat activity runs from roughly April through October, peaking from May through September. Maternity colonies, where females gather to raise pups, form in May and June. Late summer, from July into August, is often the easiest time to see bats because the young of the year are now flying and the colony is at its largest. After the first hard frosts, cave bats move to hibernation sites called hibernacula, and the migratory tree bats head south. Watch for bats swooping low over fields, water surfaces, or around streetlights where insects swarm. For more on bat behavior, check our bat page.

See our state animal guide for the next step.

To tell Connecticut bats apart in flight, note their size, wing shape, and flight pattern. Big brown bats are larger, with a wingspan around 13 to 16 inches, and fly in fairly straight, steady lines fairly high up. Little brown bats are smaller, around 8 to 11 inches across, and flutter with a more erratic, darting flight, often low over water. Eastern red bats have a rusty reddish coat and tend to fly high with a fast, direct path. The hoary bat is the largest in the state, with frosted gray fur and a broad wingspan near 15 inches, and it usually appears later and flies high. The tricolored bat is tiny and flies with a weak, moth-like flutter, often early in the evening. A handheld bat detector lets you hear their echolocation clicks and can help separate species by call frequency. For detailed species identification, visit our bat information page.