The western little brown myotis is a presence in Colorado. Open occurrence databases hold 709 Colorado records for it, but only 30 come from iNaturalist photos. The rest are museum specimens and survey captures, because a bat this small and fast is far easier to net over a pond than to photograph in flight.
Where it lives in Colorado
Of Colorado’s small brown bats, this is the great generalist. It will raise a litter in a barn attic, under a bridge, or in a rock crevice with equal ease, and it hunts midges, moths, and mayflies low over ponds, slow reaches of river, and the edges of montane forest. Records concentrate in the northern mountains and the Yampa River country around Steamboat Springs, and along the northern Front Range foothills near Boulder, which is simply where warm roost sites and standing water overlap with survey effort.
The winter gap in the record
Reports increase through the summer maternity season, when females gather in warm colonies to bear and nurse young. Then the tally falls to almost nothing. That silence is not the bat leaving Colorado; it is the bat asleep. In autumn it withdraws to caves and old mines, drops its body temperature to match the rock, and hibernates through the cold months, burning a summer’s worth of fat until spring.
A species under pressure
Colorado still lists it as apparently secure, but the IUCN now ranks the species Endangered worldwide. The cause is white-nose syndrome, a cold-loving fungus that rouses hibernating bats too often and starves them before spring. For an animal that can live more than thirty years and raises just one pup a year, that math is unforgiving, and the caves where these bats gather to hibernate are exactly where the disease spreads.
Full species profile
