The Black Hills mountainsnail is a rare and critically imperiled land snail species that is endemic to the forests of the Black Hills (i.e., only known to exist in the Black Hills). The Black Hills are an isolated mountain range located in western South Dakota and northeastern Wyoming and are nearly two million acres in size. Described as an "island in a sea of plains," the Black Hills ecosystem supports a host of animal species, such as the Black Hills mountainsnail, that exist nowhere else in the world.

Native to undisturbed forest and riparian habitats primarily in the northern Black Hills, the Black Hills mountainsnail is most often associated with springs, mature (i.e., old growth) forest, and plant communities that are associated with moist areas. The snail also requires soils with high calcium levels for shell growth and maintenance and is associated with limestone and dolomite substrates in the Black Hills. The species is extremely sensitive to habitat destruction and degradation and is vulnerable to the effects of desiccation, or the loss of life sustaining moisture. Because of this and because the snail moves relatively slowly, recovery after the effects of natural and human-caused disturbances is slow, if it even happens at all.

The Black Hills mountainsnail is an integral part of the Black Hills ecosystem and is considered an excellent indicator of ecosystem health. Because of its presence in high quality and undisturbed forest and riparian habitats, its slow movement, and its vulnerability to disturbances and/or anthropogenic habitat destruction and degradation, the species is sensitive to and responds quickly to the effects of ecological change. The status of the species therefore provides a window into the overall health of the Black Hills ecosystem, an invaluable relationship that provides innumerable social and environmental benefits.

While the species is now considered rare, the snail was once more widespread and abundant in the Black Hills. Extensive habitat destruction and degradation is believed to have caused the snail's decline and endangerment. Today, the snail is found only in areas that have remained relatively undisturbed. Most of these areas have remained undisturbed (and therefore viable as habitat for the mountainsnail) because of happenstance, not because of a conscious effort to protect the species. Conservation concern over the Black Hills mountainsnail arose in the early 1990's when the species was being considered for listing under the Endangered Species Act. Because of the species' rare status, extensive habitat destruction and degradation throughout the Black Hills, and other factors threatening the species, leading experts recommended that the species be listed under the Endangered Species Act in 1993. However, no action has been taken by the U.S. Fish and Wildlife Service to list the species or to address the threats to this unique snail. Since then, the status of the species has continued to deteriorate with inadequate or no action from state, federal, and local agencies. Population declines have continued, habitat destruction and degradation has continued, and the species is reported to be edging closer toward extinction. Now, more than ever, the Black Hills mountainsnail is in need of Endangered Species Act protection.

The Black Hills mountainsnail meets several criteria for listing under the Endangered Species Act:

• The present or threatened destruction, modification, or curtailment of habitat or range
  The Black Hills ecosystem has experienced extensive habitat loss and degradation over the last century, leading to a substantial curtailment of range and habitat. Continued habitat destruction and degradation due to domestic livestock grazing, logging, road construction, pesticide and herbicide application, mining, spring development, groundwater extraction, and recreational activities threatens to further destroy, modify, and/or curtail the habitat and range of the species.
• Overutilization for commercial, recreational, scientific, or educational purposes
  There is no indication that collecting poses any threat to the survival of the Black Hills mountainsnail.
• Disease or predation
  The Black Hills mountainsnail is preyed upon by rodents, other small mammals, amphibians, reptiles, birds, insects, and insect larvae. The species may also be parasitized by insect larvae. Because colonies of Black Hills mountainsnail have been reduced in size and extent and have become isolated due in part to habitat destruction and degradation, disease and predation may now pose a much greater risk to the survival of the species.
• The inadequacy of existing regulatory mechanisms
  The Black Hills mountainsnail and its habitat receives no protection on private lands and state and city laws are entirely inadequate to protect the snail and its habitat. Federal agencies have further failed to provide adequate protection to the Black Hills mountainsnail and its habitat on their lands and are doing nothing to recover the species and its habitat. Most egregiously, is that the United States Forest Service, which is charged with managing the majority of Black Hills mountainsnail colonies, has failed to emplace measures that effectively and assuredly protect and recover the species and its habitat despite years of concern over the status of the snail.
• Other natural or manmade factors affecting its continued existence
  Colonies of Black Hills mountainsnail have been reduced in size and extent and have become isolated due in part to habitat destruction and degradation, making the species more susceptible to extinction. Habitat fragmentation also poses significant threats to the species, making recovery of the species and its habitat difficult - if not impossible - in some instances. Floods and other natural stochastic events also pose risks to the species. Naturally occurring and human-caused fires also threaten the species and may pose greater risks as a result of extensive logging and thinning in the Black Hills. Climate change also threatens the Black Hills mountainsnail and its habitat.