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monarch-esa-petition-final_61585

monarch-esa-petition-final_61585

(Sequoia sempervirens),

(Sequoia sempervirens), coast live oak (Quercus agrifolia), and other native tree species (Xerces Monarch Overwintering Database 2014). The mild environmental conditions at forested groves along the California coast provide the microclimate that monarchs require to survive the winter in western North America. The majority of these sites are at low elevations (below 200-300 feet), within 1.5 miles (about 2.37 km) from the Pacific Ocean or San Francisco Bay (Leong et al. 2004), where these water bodies moderate temperature fluctuations (Chaplin and Wells 1982), and in shallow canyons or gullies (Lane 1993). Many groves occur on slopes that are oriented to the south, southwest, or west, which likely offers the most favorable solar radiation exposure and wind shelter (Leong et al. 2004). The suitability of habitat for overwintering monarchs is likely also influenced by landscape- and site-level characteristics that create very specific environmental conditions. These conditions include: protection from winds and storms, absence of freezing temperatures, exposure to dappled sunlight, high humidity, and access to nectar and water (Chaplin and Wells 1982, Calvert et al. 1983, Anderson and Brower 1996, Masters et al. 1988, Leong 1999). Monarch habitat includes the cluster trees that monarchs roost on as well as surrounding trees (Leong 1989, Leong et al. 1991). Fall or winter blooming flowers that provide monarchs with nectar are likely important in maintaining the lipid reserves required for the spring migration (Tuskes and Brower 1978). Pyle and Monroe (2004) suggest that the most vulnerable element of the monarch annual cycle is the overwintering stage. Monarch overwintering habitat in California is directly threatened by urban development, and to a lesser extent, agricultural development. Habitat alterations, such as tree trimming or tree removal, and natural factors such as fire, severe storms, or disease or senescence of trees, can alter the structure and microclimate of an overwintering site and reduce its suitability for monarchs (Sakai and Calvert 1991, Commission for Environmental Cooperation 2008). More than two decades ago, a statewide report documented the loss or destruction of 38 overwintering sites, 16 of which were lost to housing developments (Sakai and Calvert 1991). Eleven of these sites were lost in the period from 1985 to 1991; the remaining 27 sites were lost prior to 1985 (Sakai and Calvert 1991). In the 1990s, housing developments replaced 11 additional monarch overwintering sites (Meade 1999). The Xerces Society Database currently lists 62 sites that have likely been made unsuitable for monarchs, but many of those localities need to be monitored to determine whether monarchs have returned and assess the condition of the habitat. At present, at least three California overwintering sites are slated for housing developments (Sarina Jepsen personal observation). Anecdotal reports suggest that overwintering sites have been lost due to tree cutting or trimming (Sakai and Calvert 1991), or that the monarch population has declined after tree trimming, although this assertion can be difficult to demonstrate (see discussion in Villablanca 2010). Most western overwintering sites are dominated by Eucalyptus, which are exotic invasive species that were introduced to California from Australia in 1853 (Butterfield 1935), and have been shown to reduce biodiversity (Bossard et al. 2000). Eucalyptus removal is a restoration goal Monarch ESA Petition 72

for some natural areas (International Environmental Law Project and Xerces Society 2012), and conflicts can emerge between monarch habitat conservation and Eucalyptus removal. However, recent research suggests that monarchs do not prefer Eucalyptus trees. They use native tree species more than would be expected, given the low density of native trees relative to Eucalyptus in many overwintering groves (Griffiths 2012). Many monarch overwintering sites contain aging or diseased trees. For example, Monterey pine is affected by pitch canker (Fusarium circinatum), a fungus that causes swollen lesions that girdle branches, trunks, and exposed roots. The disease was first observed in California in Santa Cruz County in 1986 and has since spread to 18 coastal counties (Winkler et al. 2003). As aging or diseased trees lose limbs or die, sites can become less suitable for monarchs and pose a public safety hazard. In 2004, a limb from a diseased tree within the Pacific Grove monarch sanctuary fell on a visitor and killed her. Her family subsequently sued the city and was awarded a settlement of $1 million (Chawkins 2010). To ameliorate safety hazards, land managers prune aging or diseased trees, yet the removal of tree limbs may result in microclimatic changes that make a site unsuitable for overwintering monarchs. In sum, development, tree senescence, vegetation management activities, and severe weather events pose ongoing threats to monarch habitat in California. FACTOR TWO: OVERUTILIZATION FOR COMMERCIAL, RECREATIONAL, SCIENTIFIC, OR EDUCATIONAL PURPOSES Risks associated with overutilization may pose a threat to the monarch, especially in light of recent dramatic population declines and in conjunction with the many other threats facing monarchs such as habitat loss and degradation and other factors. Monarchs are reared in captivity and sold commercially for entertainment and educational purposes, such as for live releases at events including weddings, graduations, and funerals. Monarch adults and caterpillars are readily available for purchase on the internet and from catalogues. Monarchs are also sold in kits as “pets.” Capture, sell, transport, and release of monarchs can threaten the wellbeing of wild monarch populations in several ways, as illustrated by several monarch scientists and other lepidopterists (Brower et al. 1995, Altizer et al. 2014, Young-Isebrand et al. 2015). Releasing commercially-bred monarchs outside, where they can interact with wild monarchs, poses the following risks to wild monarchs: disease transmission, loss of genetic diversity, and introduction of deleterious genetic adaptations. Given that millions of monarchs are likely released each year, there is a significant opportunity for captive-bred and wild monarchs to interact. Release of captive-bred butterflies can also interfere with studies of the distribution and movement of wild butterflies which are essential to understanding their conservation needs, and increasingly important in light of climate change. Harvesting wild monarchs, a common practice Monarch ESA Petition 73

MONARCH CONSERVATION
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