Roswell springsnail Pyrgulopsis roswellensis
ESA status: endangered

Roswell springsnail pc Brian LangBitter Lake National Wildlife Refuge in Chaves County, New Mexico, is a place of unique ecological convergence, where the Chihuahuan Desert meets the shortgrass prairie and the Pecos River flows through the Roswell artesian basin. This wetland refuge is a haven for birds, and heaven for birders, who can seasonally enjoy thousands of migrating lesser sandhill cranes, Ross and snow geese, and about twenty duck species, as well as myriad songbirds and quail. Walking trails lead hikers through wetland thickets and along riverbanks, providing a peaceful getaway. But the Refuge’s most unique offering is available by appointment only...

The diverse waters of the Bitter Lake area—flowing streams, rivers, sinkholes, playa lakes, and brackish waters—shelter an incredible diversity of rare organisms. On the first Saturday of every month from October through May, you can take a guided Endangered Species Tour into parts of the Bitter Lake National Wildlife Refuge that are closed to the public. In these closed sections, you will see Bitter Lake itself, the springs which are the source of the refuge’s lakes and ponds, and around 60 sinkholes, each one a unique habitat. It is on this tour that you may have your only chance to see the tiny, rare Roswell springsnail.

This miniature snail, about the size of a Sharpie marker point (3 to 3.5 millimeters), is one member of the diverse freshwater snail family Hydrobiidae, which inhabit a great variety of specialized aquatic habitats. Hydrobiidae females are generally larger and longer-lived than males. The Roswell springsnail has specific habitat requirements: spring heads of 10 to 20°C and slow to moderate water velocity. It prefers a compact stream-bottom, either deep organic silt or gypsum sands and gravel. It has a narrow, conical, whorled tan shell. The Roswell springsnail is similar to another Bitter Lake resident, Koster’s springsnail, but can be distinguished by its dark amber operculum (the foot disk which closes the snail’s “door” when it retracts into its shell) with white spiral streaks. Koster’s springsnail has a nearly colorless operculum and is slightly larger.

The Roswell springsnail likely evolved from one of the snail species that enjoyed a broader distribution during the wetter, cooler Pleistocene around 10,000 years ago. They have a short lifespan, only 9 to 15 months, and reproduce several times during that brief opportunity. They feed on algae, bacteria, and decaying organic material.

The Roswell springsnail has only been documented on Bitter Lake National Wildlife Refuge and on private land east of Roswell. The status of the population on private land is unknown since the owner has not granted access to the property since 1998. Its core population on the refuge occurs at the Sago Springs complex and in Bitter Creek. It was once present at other springs in the Roswell area, but those springs have dried up, apparently due to groundwater pumping. Aquifer depletion and contamination from development and oil and gas drilling in the Roswell Basin are the most important threats to this species. There are at least 190 oil wells surrounding Bitter Lake that could contaminate the aquifer that underlies the refuge.

Roswell springsnails are important ecological barometers of water quality. They are very sensitive to oxygen levels, water temperature, sedimentation and contamination. Their disappearance usually indicates the loss or degradation of a pristine spring or watercourse. WildEarth Guardians fought to obtain protections this springsnail now enjoys under the Endangered Species Act, and we will continue to advocate for responsible water use and against the proliferation of oil and gas drilling and unsustainable development that threatens Bitter Lake. Our vision for the whole of the West, not just Bitter Lake, is that of clear streams and springs free of pollution and home to their full complement of unique inhabitants.

photo credit: Brian Lang, New Mexico Department of Fish and Game