Pyrgulopsis bruneauensis

This species is restricted to a single source aquifer in a small area that is experiencing ongoing declines in habitat (springs) due to the reduction of groundwater. The continued reduction of number and size of springs, as well as predation from introduced aquarium-trade fish species, will further exacerbate species declines.

This species is endemic to geothermal springs and seeps that occur along 8 kilometers (5 miles) of the Bruneau River, including portions of Hot Creek (a tributary to the Bruneau River), in southwest Idaho, USA. It has been extirpated from the upper 400 meter portion of Hot Creek (USFWS 2018).

Of the 72 geothermal springs active during a 2017 survey, only 18 were occupied (USFWS 2017). It is unknown how many constitute separate populations, but the species likely has limited capabilities to actively move between geothermal springs, especially those that are widely separated, because of the species' thermal requirements (USFWS 2018). As of 2022, there are two occurrence records maintained in the Idaho Natural Heritage Program's database (NatureServe 2022).

The continuing decline of the geothermal aquifer and the resulting negative impact to geothermal spring habitat continues to be the primary threat to this species (Idaho State Wildlife Action Plan 2017, USFWS 2018). Although seasonal high flows in the Bruneau River largely control the population size within the river, the gradual loss of springs and reduced geothermal groundwater has had a chronic adverse effect on the spring-dwelling component of the population (Idaho State Wildlife Action Plan 2017). Despite water conservation projects (e.g. in 2008 and 2015), populations continue to decline.

Predation from nonnative fishes (e.g. tilapia, guppies, and other tropical and semitropical aquarium fish) is also contributing to declines. Beaver activity has resulted in the alteration of Hot Creek and created ideal habitat conditions for nonnative fish species to thrive. If these fish populations are not eliminated in Hot Creek, "it will not be able to support a robust population of Bruneau hot springsnails" (USFWS 2018). Reducing predation may also allow for this springsnail to disperse to unoccupied geothermal spring habitats (USFWS 2002).

Livestock grazing, surface water diversions, and modification of geothermal springs for recreational use (i.e. creation of soaking pools) are additional low ranking threats (Idaho State Wildlife Action Plan 2017, USFWS 2018). Overcollection and flash flood sedimentation (at Hot Creek) were additional threats identified at the time of Federal listing (1993) but are no longer considered threats by the U.S. Fish and Wildlife Service (2018).

Furthermore, this species is vulnerable to loss due to stochastic environmental events. As its habitat and populations continue to decline, it is subject to reduced resiliency (ability of the species to withstand random disturbances, e.g. trampling, recreational use of geothermal springs) and redundancy (ability of the species to withstand catastrophic events, e.g. flash floods, high river flows) inherent in small populations (USFWS 2018).