Endangered Species
Mountain-Prairie Region

UNCOMPAHGRE FRITILLARY BUTTERFLY

Uncompahgre fritillary butterfly
Photo by Creed Clayton

The Uncompahgre fritillary butterfly (Boloria acrocnema) was discovered on Mount Uncompahgre in Colorado in 1978.  The Uncompahgre fritillary butterfly is a small butterfly with a 2 – 3 centimeter (1 inch) wingspan.  Males have rusty brown wings criss-crossed with black bars; females’ wing are somewhat lighter.  Underneath, the forewing is light ochre and the hind wing has a bold, white jagged bar dividing the crimson brown inner half from the purple-grey scaling on the outerwing surface.  The body has rusty brown thorax and a brownish black abdomen.

The Uncompahgre fritillary butterfly has one of the smallest ranges of North American butterflies.  Its habitat is limited to 11 verified sites in the San Juan Mountains.  All known populations are associated with large patches of snow willow (Salix nivalis) above 3,658 meters (12,000 feet), which provide food and cover.  The species is found primarily on northeast-facing slopes, which are the coolest and wettest microhabitat available in the San Juan Mountains.  Females lay their eggs on snow willow, which is also the larval food plant, while adults take nectar from a wide range of flowering alpine plants.

At the time of listing, threats to the species include, collection, trampling by humans or livestock, small population size, low genetic variablility, lack of protective regulations, and adverse climate conditions.

The Service was petitioned to list the species in 1979.  Subsequently, the Service included the Uncompahgre fritillary butterfly in a notice of petition findings in 1984 (49 FR 2485), which stated that listing butterfly was warranted but precluded.  The butterfly was then listed as endangered in 1991 (56 FR 28712), because of its small geographic range and the declining population.  The recovery plan was published in 1994.

On April 18, 2007, we published an announcement initiating the 5-year review process and seeking new information on the Uncompahgre fritillary butterfly (72 FR 19549).  In 2009 the Service published the final 5-year review, which suggested downlisting the Uncompahgre fritillary butterfly to threatened status.  Since listing and the completion of the Recovery Plan, the number of confirmed colonies has increased from 2 to 11, threat of collecting appears to have been forestalled by maintenance of Uncompahgre fritillary butterfly collecting closures around the two well-known colonies, climate change has not been an observable threat to either the butterfly or its habitat to date, and although there is fluctuation in the colony population numbers, adequate quality habitat exists producing what appears to be stable population numbers.

Last updated: May 4, 2010