It is made out of dry grass, leaves and finely shredded material. Both adults care for the young, which are weaned at 21 days. Least shrews may have 2 to 3 litters per year. The greatest threat facing Connecticut's least shrews is the development of coastal habitats, which results in the isolation of breeding populations. The chances for any individuals from these populations to move to other areas of suitable habitat may be limited or non-existent under these circumstances.
Development also limits the amount of available habitat.
Other threats include pesticides and pollutants that contaminate food and habitat. In 1840, the species was first reported in Darien by Reverend James H. Linsley, who was better known for publishing bird lists. The species was not found again in Connecticut for 100 years. In 1941, George Goodwin, Assistant Curator of Mammals at the American Museum of Natural History, in New York, found one in Westbrook while walking along the edge of a saltgrass meadow. For almost 50 years since Goodwin's report, the secretive least shrew again remained unseen until one was found in coastal Middlesex County in 1989.