The population ecology of this species is exceptionally difficult to study as a result of the small size of individuals and the type of habitat they occupy. This species is known to swarm in large numbers, a condition that is likely important for reproduction. Mating occurs in the fall. Fertilization is delayed to spring and gestation lasts about 40 days. It has been suggested that two young may be produced but one appears to be the most common pattern, at least in California.
Maternity colonies are small, comprised of fewer than a dozen individuals.
Keller, B.L. 1995. The status of bat populations in the Craig Mountain Area, Nez Perce County, Idaho. Cooperative Challenge Cost-share Project, Idaho Department of Fish and Game and Bureau of Land Management, Boise, Idaho.