Overview:  The Snake River physa snail is at home within the fast-flowing, cool waters of the Snake River's main branch.  Burying itself withing the gravel or anchoring itself to the underside of a rock, the physa feeds on microscopic prey, such as algae and diatoms.  Dams built along the Snake River have slowed the natural pace of the river to the extent that the physa is unable to survive in much of its former range.  The warmer, slower waters that characterize a large portion of the river trapped behind a dam do not supply the physa with sufficient amounts of oxygen.  Increased levels of water pollution, as well as competition with the more tolerant, non-native mud snail, are also threatening the continued survival of this species.  The U.S. Fish and Wildlife Service has a recovery plan for the Snake River and its endemic species, which you can view at http://endangered.fws.gov/recovery/recplans/index.htm.

Distribution: According to fossil records, the range of the physa used to include portions of Utah and southeastern Idaho.  But its distribution is now limited to a few locations in the Hagerman and King Hill reaches of the Snake River, with a separate population near Minidoka Dam.