The U.S. Fish and Wildlife Service (USFWS) is proposing to list a subspecies of silverspot butterfly as threatened under the Endangered Species Act (ESA) after conducting a peer-reviewed species status assessment (SSA).
The environmental group WildEarth Guardians petitioned USFWS in 2013 to list the silverspot butterfly for protection. In 2016, USFWS found the petition presented “substantial scientific or commercial information indicating that the petitioned action may be warranted” and began reviewing the species for the listing.
The silverspot butterfly can be found in elevations of 5,200 to 8,300 feet across southwestern Colorado, eastern Utah and northern New Mexico. The butterflies have a 3-inch wingspan with distinctive silvery-white spots on the underside of their wings. On their upper side, females have a cream or light yellow coloring with brown or black, and males have a bright orange upper side.
They require moist, open meadows for nectar sources and lay their eggs on, or immediately next to, the bog violets that the larvae feed on exclusively. The eggs hatch approximately two weeks after being laid in September, and the larvae immediately drink water before going dormant until May. When the bog violets flower in May, the larvae begin feeding on them into July.
According to the release, “While the silverspot butterfly is not in immediate danger of extinction, the best available scientific information indicates that it is in danger of extinction in the foreseeable future.”
The SSA states habitat loss is due to fragmentation, incompatible livestock grazing, human-caused hydrological alteration, genetic isolation, climate change, invasion by nonnative plants, fires and pesticides, which influence or could influence species viability.
The SSA notes there are 19 colonies representing 10 populations, and little conservation effort has been directed toward the silverspot butterfly. The two measures that occurred were both in Mesa County, Colorado, in the Mesa/Grand population. The authors stated that housing development and a golf course in Durango, CO, and Beulah, NM, caused habitat loss. Additionally, agricultural conversion has occurred within the range of the butterfly.
The SSA states that grazing may cause habitat loss and degradation if excessive, especially in naturally scarce habitats. “Summer grazing is typically incompatible because livestock graze on the violet leaves, nectar sources and other vegetation necessary for the butterfly when the larvae and adults need them,” the report states.
The SSA notes that the spikerush and willow invasion in the Unaweep Seep colony in the Mesa/Grand population contributed to the loss of habitat. It is unknown if it would have occurred without grazing.
“Grazing is ongoing in suitable habitat for the species and can limit the availability of habitat throughout the range. Though it can be compatible, it is expected to continue to be a major factor influencing species viability,” the report continued.
According to the release by USFWS, the agency is considering an accompanying 4(d) rule to the threatened listing, which would support tailored conservation of the species with balanced land management to allow continued acceptable land uses.
The proposed rule to list the silverspot butterfly as a threatened species and the accompanying 4(d) rule will be open for public comment until July 5. To comment, you can visit www.regulations.gov and search for document ID 1018-BE98. — Charles Wallace, WLJ editor
