The Bay checkerspot butterfly (Euphydryas editha bayensis) is a federally threatened insect species which is native to the U.S. State of California. Since the 1980s the population of Checkerspots has been in serious decline. Because this particular species is so well studied and observed the decline was quickly recognized leading to its federally threatened status relatively quickly in 1987. Recently, researchers have advocated a reclassification for this subspecies of the checkerspot common to western North America, Euphydryas editha. The classification, to Euphydryas editha editha, is for reasons of historical precedence.
Adult butterflies emerge in early spring. The adults, which live an average of ten days emerge during a six week period from late February to early May. The male Bay checkerspot typically emerges four to eight days before the female. The males have one goal, reproduction. They find and mate with a female immediately upon emerging. The male mates many times while most females mate only once during the flight season. Besides mating the adults spend time foraging for nectar and for the females, laying eggs.
The eggs are usually laid in March and April. The adult female will lay up to five masses of eggs which contain 2 to 250 eggs each. The eggs are deposited at the base of the dwarf plantain plant or less frequently the owl's clover or paintbrush. The eggs take about ten days to hatch and upon emergence from the eggs the larvae grow for a period of two weeks or more during which they shed their skin up to three times. Any larvae that successfully enters the fourth instar enter a period of diapause that lasts through the entire summer. During diapause they spend time under rocks or within cracks in the soil. When the diapause ends they resume activity, feeding and move to complete their development into adult Bay checkerspot butterflies.
The historic range of the Checkerspot included many areas around the San Francisco Bay. Most of the San Francisco peninsula, mountains near San Jose, Oakland hills and several locales around Alameda County were once home to populations of the butterfly. Areas east, west and south of the bay, from Twin Peaks to Mount Diablo in Contra Costa County, all the way south to Hollister, the butterfly occurred. Many of these areas no longer hold the species as development of the area increased throughout the 20th century. Today the only populations known inhabit areas of San Mateo and Santa Clara Counties. Disturbances, specifically the altered regimes of these disturbances (i.e. fire, grazing) have, along with invasive grassland plants, induced decline in the population of the host plants.
The current range is much reduced and patchy at that. Of all occurrences of the butterfly known when the species was listed as threatened in 1987, all in San Mateo County have disappeared. The exception is a reintroduction of approximately 400 larvae to Edgewood Park in February 2007. The species was last observed at San Bruno Mountain in 1985 and at Jasper Ridge Biological Preserve in 1998. All remaining known populations of the butterfly are in Santa Clara County. The U.S. Fish and Wildlife Service recommends that any area of appropriate habitat within the historic range should be considered "potentially occupied." One site in Santa Clara County that has a large source population, that may number in the hundreds of thousands, is near the City of Morgan Hill on a ridge line currently called Coyote Ridge.
In the area of Jasper Ridge Biological Preserve local populations were deemed extinct in 1998. The populations of butterflies at Jasper Ridge had been the subject of intensive study and research at the lead of Stanford biologist Dr. Paul Ehrlich. Ehrlich had studied the Jasper Ridge populations since 1960 and researchers were able to examine 70 years of climate data and conclude that gigantic fluctuations in local climate probably hastened the demise of the Jasper Ridge Bay checkerspot populations. Ehrlich contends that prior to Spanish settlement of California the Bay checkerspots were almost certainly ubiquitous in California. It was the inadvertent import of invasive plant species in the hay that settlers fed cattle that brought unnatural competition for the native plants that sustained the Bay checkerspot.
The butterfly and its host plants thrive in areas with serpentine soil, soils derived from the serpentine mineral, and other ultramafic rocks. The habitat has been described as consisting of three general types. Type one is the primary habitat which occurs on native grasslands located upon very large serpentine outcroppings. Type two is secondary or "satellite" habitat "islands" which occur in native grasslands on smaller serpentine outcrops. These satellites are typically generating very robust populations of Bay checkerspots in favorable whether with good habitat conditions. Type three are the tertiary habitats. These areas are where both Bay checkerspot larva and the plants they feed on occur in non serpentine soils with similarities to serpentine derived soil.
The possible reclassification of Euphydryas editha bayensis would indicate a change in range for the Bay checkerspot because of several populations of checkerspot butterflies whose subspecific status has been uncertain. If the nomenclature change was accepted it could represent a range extension for the threatened butterfly.
Plantago erecta is native to California and only found in western North America. As the primary host plant for the Bay checkerspot the plantain is an important species for conservation of the butterfly. Known by a host of common names, as many plant and animal species are, its nomenclatures include California plantain, English plantain, Foothill plantain, dotseed plantain, and dwarf plantain. This plantain is typically found in coastal sage scrub, foothill woodland, and chaparral biomes.
C. exersta, it is known by a handful of common names,Exserted Indian paintbrush, sometimes Red owl's clover, or Purple Indian paintbrush as well. It is one of two secondary larval host plants of the butterfly that remains edible later in the season and acts as a back up when the dwarf plantain dries up. The plant can grow up to 16 inches in height. It prefers mesas, slopes and open areas in ponderosa pine forests and poppy fields at elevations from 1,500 to 4,500 feet (1,370 m). The flowers bloom from March to May and are about 1.25 inches long and formed in dense spikes, they are a magenta or purple color on the lower corolla lips and have yellow or white tips. The bract, modified leaves, are a reddish purple and hold 5 to 7 lobes, each about one inch long. It ranges from middle to southern California, into southern Arizona and northern Mexico.
The plant's original classification, Orthocarpus purpurascens, has been shown, after careful study, to have been incorrect. Study showed that it belonged to the lineage of Castilleja.
The USFWS has identified several of these areas as core habitat areas, which it considers essential to the survival of the species. These areas include some of those mentioned above and others. Areas along the Coyote Ridge, including Kirby, Metcalf, San Felipe, Silver Creek Hills have been designated "core habitat areas." An area of 1,100 acres (4 km²) in the Santa Teresa Hills has been labeled a "potential core area" by the Wildlife Service. The Service also denotes some other areas, near core populations, of good quality, meaning suitable habitat. Tulare Hill is one of those areas and along with the Santa Teresa Hills and Redwood City, is considered a "stepping stone."
Increasing nitrogen emission is a problem facing the delicate balance within the ecosystems that contain the Bay checkerspot in many areas. At Coyote Ridge the problem is well documented by conservation biologist Stuart Weiss. While faced with a declining population of Bay checkerspots at Coyote Ridge, Weiss searched for a causality. He found the link between a combination of pollution from the freeway below the ridge and, again, a cutback in cattle grazing locally. Weiss documented how nitrogen oxide emissions from cars enriched the nutrient poor serpentine soil. This is a prime example of the nitrogen effect explained above. Aside from helping decrease nitrogen the cattle also help to control invasive grasses by eating them. Any question about whether or not nitrogen emissions from cars traversing Highway 101, 110,000 vehicles daily, evaporate when faced with monitoring statistics from Weiss. His monitoring equipment has confirmed that 15 to 20 pounds of nitrogen per acre are deposited on Coyote Ridge annually. Some of the particles stick to the plant and ground and are washed into the soil, still others are directly absorbed by the plants themselves. By contrast, pollution from power plants and vehicles drop only about four to five pounds of nitrogen per acre per year on the Jasper Ridge preserve.
Other goals of the Jasper Ridge study include, analyze the regulatory framework for endangered species and how changes might aid recovery of species, characterize the genetics of research collections and possible donor populations and to look at the historical changes in ownership, management and condition of the serpentine grasslands that the Bay checkerspot calls home.
The region known as Coyote Ridge refers to an unnamed ridge in Santa Clara County. A variety of names have been applied to areas along the ridge where known populations of Bay checkerspots have or do currently live. Some of these names include, Morgan Hill, Kirby Canyon, East Coyote Foothills and, of course, Coyote Ridge. The U.S. Fish and Wildlife Service identified four core areas along Coyote Ridge that require attention as Bay checkerspot habitat. They have termed them Kirby, Metcalf, San Felipe and Silver Creek Hills.
Projects at Kirby Canyon were behind the original schedule in the late 1990s. Revegetation efforts were slowed in large part due to lower than expected rates landfill filling. Waste Management fulfilled the ten year duration of the agreement and offered after to fund 50 percent of the agreement for three additional years.
It was a housing and golf course project that spurred the creation of the Silver Creek Butterfly Conservation Area. The homes were built, about 1,500 of them, and the golf course went in on about 1,500 acres (6 km²) in the Silver Creek Valley, east of San Jose. The project resulted in the loss of about 18.5 acres of serpentine habitat for the Bay checkerspot. As compensation the developer, Shea Homes, in 1991, established a permanent 115 acre site for butterfly conservation in the Silver Creek Hills. The company also provided for ten years of monitoring of the preserve. Shea Homes also deposited $100,000 into an account dedicated to regional conservation of the Bay checkerspot, money now managed by USFWS.
With the Silver Creek Butterfly Conservation Area up and running the area population of Bay checkerspots increased markedly. By 1994 there were tens of thousands of adult butterflies. This population crashed in 1995 and 1996 due to problems implementing necessary management actions. By 1997 no post-diapause larvae were found and only three adults were observed during annual monitoring. Other populations are located on nearby property in the Silver Creek Hills and the nearby San Felipe habitat area.
The preserve was threatened by a proposed golf course development in 1983. A 1993 resolution helped secure the park's future. That year the San Mateo County Board of Supervisors closed the golf course issue when they adopted a resolution that designated Edgewood Park "a scenic natural area where outstanding features as well as significant wildlife habitats are preserved in their present state for the enjoyment, education and well-being of the public." At the same time the county also modified their agreement with Midpeninsula Open Space District, adding a clause to prohibit golf course development and emphasize natural resource preservation and low intensity recreation. The Bay checkerspot went locally extinct during the early 2000s, last observed at Edgewood Park in 2002. This local extinction was attributed to nitrogen deposition from cars traveling on adjacent Highway 280, which fertilized invasive Italian ryegrass and choked out native plants required by the butterflies. Subsequently, the habitat was restored by mowing at an appropriate time of year to reduce the Italian ryegrass and allow the native plants to regrow. In early 2007, 1000 Bay checkerspot larvae were reintroduced to the park.