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Puget Trough prairie butterfly
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Overview Butterfly conservation is a complex issue that requires more than just preserving habitat. Prairie butterflies such as the Taylor’s checkerspot, Puget blue, Mardon skipper and the Zerene fritillary are under attack due to many threats such as urban sprawl, forest encroachment, pesticide use, as well as the proliferation of nonnative fauna species. This can make the task of preservation more difficult, because many of the species have started to adapt to the current environmental conditions (Ehrlich, 1992). This means that we need to pick and choose our conservation battles carefully. Since many of the populations are already at severe risk of disappearing even our best intentions could finish off species that are already on the brink. Many of the sites where these beautiful creatures live are also over run by nonnative species, such as the grass tall fescue, Festuca arundinacea. Traditional management strategies have been to eliminate any nonnative species and try to reestablish native vegetation. This sounds like a good idea, but over time some native butterfly species have adapted to use nonnative species as host plants to lay their eggs, or as a nectar source (Ehrlich, 1992). Many times nonnative species can do more harm than good, but this needs to be investigated on a case by case basis. Some native butterflies such, as the Taylor’s Checkerspot choose host plants based on the habitat where the plants are found rather than selecting their traditional native plant species (Ehrlich, 1992). This means that one of the biggest threats to the future success of these species could be our efforts to save them. We need to prioritize our preservation efforts to ensure that the actions we take don’t become the biggest threats to the survival of these species. Taylor’s Checkerspot (Euphydryas editha taylori) Description The Taylor’s Checkerspot, also known as the Whulge Checkerspot is the darkest subspecies of the Euphydryas family. This butterfly has a wing span of less than 2.25 inches. It gets its name from the checkered color pattern on its wings that consist of black, orange and white coloring (Black, 2005). Taylor’s Checkerspot once ranged from the Willamette Valley in Oregon to Vancouver Island in British Columbia. Conservation status The Taylor’s Checkerspot butterfly is at extreme risk of going extinct (Black, 2005). It has been a candidate species for the U.S. Endangered Species act since 2001. In Washington it is listed as a species of concern and has an active conservation program. In Oregon Taylor’s checkerspot is on the Threatened and Endangered Species list, but receives no protection under state statute. Before its dramatic decline the Taylor’s Checkerspot was documented at more than seventy sites, but is currently found only at twelve sites in Washington and two in Oregon (Black, 2005). Canada has listed the subspecies as endangered since 2000 and it is currently extirpated from British Columbia (Black, 2005). Threats The biggest threat to its survival is the loss of prairie habitat due to European settlement. Since our arrival more than 99 percent of the lowland prairies have been destroyed. The reason for this is that prairies are prime locations for agriculture as well as development of all types due to the lack of trees and flat topography (Bock, 2007). Along with habitat loss the subspecies is impacted by pesticide use that makes their plight even worse (Fimbel, 2004). Increased risk of harm due to drought is another major concern since they are now stuck on these patches of habitat with no chance to migrate to more suitable places. Puget Blue (Icaricia icarioides blackmorei) Description The Puget Blue is a small blue and grey butterfly with a wingspan of around 1.8 inches in the Lycaenidae family. The male has dorsal wings that are a silvery blue with a wide dark margin. The female is grey-brown with diffuse blue patches at the base of the wings (Fleckenstein, 2006). The range of this species spans from Vancouver Island and The Olympic Mountains in Alpine to Subalpine habitat to the lowland prairies of the South Puget Sound. Conservation status At this time, the Puget Blue has not yet been designated endangered or threatened by the federal government, but it is a candidate species for restoration in the State of Washington. Populations in the prairies have declined due to the loss of prairies as well as the encroachment of woody vegetation such as Douglas-fir (Pseudotsuga menziesii) and Scotch broom (Cytisus scoparius). Threats Scotch broom out-competes the host plants of this butterfly species and as a nitrogen fixer it alters the natural nutrient balance in the soils. Because many prairie species, such as their host plant, the lupine (Lupinus lepidus), have adapted to thrive on much lower nutrient levels the increased nutrient loading greatly inhibits the lupines ability to thrive (Grosboll, 2005). The subalpine populations have increased as logging activities have cleared land allowing the expansion of their host plant the lupine (Fleckenstein, 2006). The biggest threat to the subalpine populations is climate change, while the prairie populations are most threatened by habitat loss and fragmentation. Land management techniques used to maintain prairies such as controlled burns, can either help or hurt populations of native butterflies. If timed correctly controlled burns can greatly increase that year’s lupine crop, giving the Puget Blue a better chance at success (Fleckenstein, 2006). Mardon skipper (Polites mardon) Description The mardon skipper is a small size (< 1in) butterfly that belongs to the Hesperiidae family. Its habitat extends from the northwestern coast of Washington, through southern Oregon and northern California. In Washington, the Mardon skipper can be found in the Puget prairies and the South Cascades (Potter, 1999). Some distinguishing characteristics of this species are an orange hairy body with dark orange accents on the upper surface and a light orange lower surface with white-yellowish rectangular spots (Potter, 1999). Male specimens are known to be darker than females as well as smaller in size. Other species with very similar attributes include the Sonora skipper (Polites sonora) and the woodland skipper (Ochlodes sylvanoides). This butterfly species, native to the northwest, is most commonly found on prairies populated by native grasses such as Roemer’s fescue (Festuca roemeri) and red fescue (Festuca rubra). These native plants serve as oviposition sites (Beyer and Schultz, 2010). Some of the native plants that provide the species with nectar include the early blue violet (Viola adunca), prairie lupine (Lupinus lepidus), as well as Idaho blue-eyed grass (Sisyrinchum idahoense), penstemon (Penstemon spp.) and vetch (Vicia spp.) Conservation status The mardon skipper butterfly is currently listed as an endangered species in Washington State and classified as a federal endangered species. Its status denotes a high priority for conservation efforts. Over the years, studies have been assessing the decline of this species in the Puget prairies, by conducting population counts and habitat characteristics and their effect on the Mardon skipper’s life cycle (Beyer and Schultz, 2010). Threats The mardon skipper is a non-migratory species, so its response to changes in habitat is minimized, especially during the larval stage. This species is known to prefer open grasslands populated by native plants that can serve as host plants as well as nectar sources. Their optimal habitat can be easily degraded through conversion and fragmentation, increase in invasive species, as well as changes in weather and human actions (Beyer and Schultz, 2010). Zerene Fritillary (Speyeria zerene bremnerii) Description The zerene fritillary is a small size (< 2.5 in) butterfly species that belongs to the Nymphalidae family. The species distribution ranges from southwestern British Columbia to south-western Oregon. In the state of Washington, the species is commonly found on the San Juan Islands, as well as the Washington coast range and the Puget prairies (Foltz, 2009). Some distinguishing characteristics of this species include a larger size than the other species from the same family and an orange-red body with prominent silver spots on the dorsal side (Foltz 2009). The zerene fritillary species commonly inhabits grasslands, forest edges and transition zones (Foltz, 2009). The availability of host and nectar sources influences the distribution and success of the species. The fritillaries are known to use certain plants for oviposition such as the native blue violet (Viola adunca) and use several plants as nectar sources: Solidago spathulata, Aster curtus , Sericocarpus rigidus, Senecio jacobaea, Leontodon nudicaulis and Cirsium arvense (non-native) ( Fimbel, 2004). Conservation status Currently, the fritillaries are considered a species of concern at federal level, while at the state level they are considered to have medium priority for conservation efforts (Fimbel, 2004). Threats One of the main concerns regarding the survival of this species is the host plant availability. The early blue violet is frequently in competition with both herbaceous and woody invasive species. This not only inhibits the growth of the violet but also restricts the females from having access to their oviposition site. Furthermore, food sources are also affected by growth of invasive species, land loss, as well as maintenance practices. Conservation strategies: A comprehensive conservation plan can only be devised if the factors responsible for the decline in the populations of these four butterfly species are fully understood. While the habitat requirements are similar among these species, the smallest changes can have drastic impacts. This is a product of their strong dependency on the characteristics of their native habitat and the inability to migrate. Butterfly species rely strongly on the plant species that are present in the grasslands. The fragmentation of prairie habitat has caused a decrease in overall habitat diversity. Furthermore, agriculture, urban development, increase in anthropogenic activities have all caused habitat fragmentation. Smaller patches of habitat are more susceptible to be further threatened by both native and invasive woody species (Fimbel, 2004). Butterfly populations can only thrive if resources are available at both larval and adult stage. A reduction in overall diversity leads to fewer host and nectar sources, both of which are critical for survival (Schultz, 1998). Control practices must be carefully chosen in order to preserve the existing habitat. Maintenance practices such as burning and grazing can have unfavorable effects on butterfly populations. The removal of invasive species must be accomplished in a way that promotes the growth of native species that act as hosts and nectar sources. Previous studies recommend management practices that would combine or alternate fire control and grazing, because not all species will have the same response (Vogel, 2007). Management and restoration practices that include fire control must take in consideration the immediate effects that the burns will have on butterfly populations and carefully assess the trade-offs of this process. While the vegetation composition may benefit from the burn, some butterfly populations could be eradicated. Researchers recommend the use of a “butterfly-sensitive” burn plan that would include planning fire events on particular sections of the prairie habitat targeted for restoration (Fimbel, 2004). Conservation practices The survival of these four butterfly species is strongly reliant on the quality of the resources offered by habitat. Factors that should be taken into consideration are the vegetation structure, as well as the habitat’s diversity. In order to conserve and restore the existing prairie habitat, a well thought-out combination of practices must be implemented. Such practices include the control of non-native vegetation as well as native woody vegetation, and enhancement of native prairie vegetation. The quality of the habitat is increased by promoting diverse native vegetation. This process benefits butterflies throughout their life cycles by assuring the existence of host plants as well as nectar sources. Control of non-native vegetation Some short non-native species such as Plantago lanceolata and Cirsium arvense provide nectar for some butterfly species, but taller species such as Scott’s broom are known as threats. Tall non-native species not only reduce the success of the native vegetation present on site but also pose and impedes the reproduction process of the butterflies by reducing the ease of access to the oviposition plants (Fimbel, 2004). The reduction of non-native vegetation can be accomplished by using a combination of methods such as fire, application of herbicides, grazing and mowing. Fire Fire is one of the oldest methods used to control the non-native vegetation of the prairies. This method was employed by the Native American tribes that managed the prairies to enhance populations of food and fiber plants for thousands of years. In current times, with the development of military forts, prescribed burnings have replaced the fire regimes created by Native American tribes. Most commonly, fire is used to prevent the encroachment of Pseudotsuga menziesii into the grasslands (Fimbel, 2004). Using fire as a control method can create both positive and negative impacts on the butterfly population. While fire has the ability to reduce non-native species and promote seed germination of some native species, it is also very likely to cause mortality of butterfly species if timed when eggs, larvae or pupae are prevalent. Burning should only be done during the non-flight periods and only over less than a fourth of the total butterfly patch. It is recommended for burning to be avoided during the months of August, September and October (Fimbel, 2004). Herbicides applications Herbicides such as sethoxydim have the ability to destroy non-native grass species but not harm broad leaf species (Fimbel, 2004). By reducing the density and growth of non-native grasses, there are more resources available for native species, which in turn creates more host plants and nectar sources for the native butterfly population. The eradication of tall grasses also makes it easier for butterflies to access resources needed for their survival. As with other methods, this could also bring negative impacts such as harming certain native grass species that could be used as host plants (Fimbel, 2004) Mowing This method should be used sparingly because it lacks the ability of targeting specific individuals. While the short species might not be endangered by this process, taller native species might be harmed and this could lead to a less diverse native vegetation composition. Grazing Grazing cattle or sheep on the land is considered a better alternative to mowing. Previous studies have shown that cattle have a preference for non-native grasses, which lessens the impact on the desired plant species (Fimbel, 2004). Therefore, this practice eliminates non-native species while promoting higher biodiversity (Vogel, 2007). While all the above mentioned practices are meant to suppress non-native plants, they should be conducted while keeping in mind factors such as the life cycles of the butterfly species present on site, as well as the vegetation composition surrounding the targeted areas. Control of woody vegetation Woody vegetation (trees and shrubs), even when native, should be taken into account when habitat threats are assessed. Shrub species such as Rubus armeniacus and Symphoricarpus albus have negative impacts on the native prairie vegetation (Fimbel, 2004). Similar to Scott’s broom, these species out-compete native herbaceous species and restrict access to host plant and nectar sources. In order to keep such species under control, treatments such as fire, herbicides and grazing can be used. Enhancing the composition of native vegetation A diverse composition of native vegetation is essential for the survival of these four butterfly species. While certain control practices help suppress the encroachment of non-native species, the effect that these methods have on the native species should be taken into account when formulating maintenance plans for prairie habitats. Native vegetation eliminated by invasive control practices should be replaced in order to preserve the habitat’s diversity. The native plants that act as host species, as well as the nectar sources, should have top priority in this process. Such plants are : Solidago spathulata, Aster curtus , Sericocarpus rigidus, Senecio jacobaea, Leontodon nudicaulis, Roemer’s fescue (Festuca roemeri), red fescue (Festuca rubra). (Viola adunca), prairie lupine (Lupinus lepidus), as well as Idaho blue-eyed grass (Sisyrinchum idahoense), penstemon (Penstemon spp.) and vetch (Vicia spp.) (Beyer and Schultz, 2010). Butterfly species such as the Taylor’s Checkerspot, Puget blue, Mardon skipper and the Zerene fritillary act as indicators of overall prairie health. In order to offer these four butterfly species the best chance at survival, our conservation efforts must be focused on multiple factors affecting their life cycle such as: presence of native host plants and nectar sources, nitrogen levels in the prairie soils as well as the invasive species that may threaten them. It is recommended that conservation practices be based on both maintaining the current extent of the prairies as well as the success of the species populating it. Prairie enhancement methods such as fire and grazing may bring both positive and negative impact on the butterfly species; therefore these practices should take into consideration all the factors that influence the key life stages of these four butterfly species (Beyer and Schultz, 2010). While we discussed many negative impacts to the places where these wonderful creatures live there are many positive things taking place from the highest levels of government down to grass root movements that are really making a difference. If this trend continues, the future of these prairie butterflies could be bright. The public at large is realizing what an important role these species play besides just being beautiful to look at. With progress like this, real and meaningful change is not only possible but already happening. <references /> See Also
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