Behren's Silverspot Butterfly- Christine Bradley

https://www.fws.gov/arcata/es/inverts/BehrensSS/gallery/

Behren's Silverspot Butterfly
 Behren’s Silverspot Butterfly (Speyeria zerene behrensii) is native to California. The wingspan of this butterfly is 5.5
cm (2.2 inches) and is a subspecies of Zerene Fritillary, or silverspot butterflies. There are 13 species of butterflies belonging to the true fritillary family in North America.  This butterfly is characterized by its noticeable brownish orange color with black lines and dots on its wings. This butterfly flies erratically above ground (2 to 6 feet) in windy places in its native range is on the California coast from southern Mendocino to northern Sonoma Counties. This butterfly is a specialist species that relies on violets, particularly the early blue violet for its source of nectar for adult butterflies, and oviposition for caterpillar and larval survival.

Geographic Range of the Behren's Silverspot Butterfly
https://ecos.fws.gov/ecp0/profile/speciesProfile?sId=900

Geographic Range

The Behren’s Silverspot Butterfly seeks early blue violets as larval food plants; the larvae spin a silk pad a short distance from where they hatched. This silk pad is used for diapause (dormancy) in the fall and winter, but the five instars (caterpillar growth stages) take place in the spring and summer. Upon completion, the caterpillar forms a pupa for two weeks before emerging as an adult butterfly but will only live for about another three weeks. This butterfly relies on a habitat that satisfies factors such as close proximity to the ocean, common summer fog, moderate rainfall, and mild temperatures. The prairie-like habitat of this butterfly has faced fragmentation due to agriculture, human development, and use of roads/residential areas. The fragmentation of the butterfly’s habitat has led to the endangerment the Behren’s Silverspot Butterfly.The dunes at the southern end of Manchester State Park, Mendocino County are known to support silverspot butterflies, but these dunes have been subjected to habitat fragmentation and anthropogenic development.
Listing Date

This species was listed as endangered on December 5, 1997, by the U.S. Fish and Wildlife Service. During the time of the listing, a critical habitat was not designated for the Behren’s Silverspot Butterfly, this was out of concern due to the impact of threatened and endangered butterflies. This species is now only found at a single location in Mendocino County, California, as it has been extirpated from its previous five other locations.

Blue Violet
https://www.usda.gov/media/blog/2010/08/6/helping-threatened-butterfly-recover-oregon

Threats and Limiting Factors

            Major threats and limiting factors to the Behren’s Silverspot Butterfly are degradation of the habitats, exotic vegetation, livestock grazing, development, and butterfly collecting. The coastal terrace prairie habitat is affected by soil conditions, salt spray and mist, and disturbance regimes. Vegetation growth is limited by soil depth and texture. Sandy or rocky soils cannot hold moisture that is vital for the blue violets, but clay soils have flooded the violets in previous years. Additionally, exotic grasses such as heath grass, bent grass, velvet grass, and orchard grass produce tall or dense stands which eliminate native plants, such as blue violets which the butterflies depend on for survival as a specialist species. Livestock grazing is another threat to the Behren’s Silverspot Butterfly due to the interference of domestic animals on the butterfly’s habitat. The Fish and Wildlife Service lists livestock grazing as a major disturbance agent to this species. A significant source of butterfly mortality is due to overgrazing host plants and trampling. Another threat to this species is the agricultural, residential, and commercial development which have degraded the butterfly’s habitat. An example of this was the construction of Highway 1 which runs along the California coast. Development of this highway not only fragmented the habitat but had effects on the ecosystem by traversing watercourses and providing public access. Much of the coastal terrace prairie has been converted in the agricultural land to grow crops. Butterfly collecting is the final threat to the Behren’s Silverspot Butterfly. The illegal trade of threatened and endangered species continues to deplete the populations of this species.

Recovery Plan

            The recovery objective detailed by the Fish and Wildlife Service is to, “Recover the subspecies to the point where it can be delisted.” The estimated cost of recovery is $10,500,000. Several actions can be taken to increase population numbers.

Firstly, protecting the existing habitat from destruction or degradation will benefit the butterflies by saving the native host plants and providing optimal conditions. Currently, the only known population of this species is on a private ranch near Point Arena in Mendocino County. The land is not owned by a land trust, so it is crucial that conservationists acquire the land to protect the metapopulation once the land is for sale. It is vital that land purchased from the ranch does not go towards agricultural or commercial development. Additionally, suitable habitat for the blue violet needs to be assessed for soil type, erosion, and other environmental factors to sustain the re-introduction of the species. Artificial techniques such as captive breeding and translocation to a new habitat may be needed to support the small population. Finally, reducing the capture of the species by butterfly collectors can be achieved through education and outreach programs. The public should be made aware of the threats to this species because their compliance with protective measures is crucial for the repopulation of the butterflies.

The Fish and Wildlife Service states that the Behren’s Silverspot Butterfly can be downlisted to “Threatened” when the population has reached over 4,000 individuals in ten years, with protected metapopulations having no less than 1,000 individuals. Furthermore, this species can be delisted from the Threatened and Endangered list when six metapopulations have been established. To be delisted, each of the six metapopulations must have no less 1,000 individuals and the species must have at least 6,000 adult butterflies for ten years. The species can potentially be downlisted by 2028 and delisted by 2038.

Our Role in Recovery

            Education is the key to the survival of the Behren’s Silverspot Butterfly. An outreach program that informs the public about threats to this species can help increase the population numbers by reducing the take of the butterflies and destruction of habitat. Private land that is purchased should be used to help the recovery of this species if the habitat is suitable. The public should be aware of habitat destruction, overgrazing, and agricultural or commercial development of land. By informing the public and doing our part, we may be able to save this endangered species from extinction.

Resources
 "Behren's Silverspot Butterfly (Speyeria Zerene Behrensii)." ECOS Environmental Conservation Online System. U.S. Fish and Wildlife Service, n.d. Web.

U.S. Fish and Wildlife Service. 2015. Recovery Plan for Behren’s Silverspot Butterfly (Speyeria zerene behrensii). U.S. Fish and Wildlife Service, Pacific Southwest Regional Office, Region 8, Sacramento, California. xi + 95 pp.

U.S. Fish and Wildlife Service. “Behren's Silverspot Butterfly Species Profile.” Official Web Page of the U.S. Fish and Wildlife Service, Arcata U.S. Fish and Wildlife Service, 5 Dec. 1997, www.fws.gov/arcata/es/inverts/BehrensSS/bss_bfly.html.