monarch-esa-petition-final_61585

two highly invasive swallow-wort species that are widely distributed in the United States—black
swallow-wort (Vincetoxicum nigrum, synonym Cynanchum louiseae L.) and pale swallow-wort
(V. rossicum, synonym C. rossicum). Black swallow-wort is found from Maine through Kansas
and in California. Pale swallow-wort is discontinuously distributed from the Great Lakes through
New England and the Mid-Atlantic States. Both swallow-wort species out compete milkweed
and also serve as dead-end hosts for monarch oviposition because monarchs lay eggs on them
due to chemical cues similar to milkweeds, but larvae do not survive (DiTommaso and Losey
2003, p. 205, Casagrande and Dacey 2007, p. 632, 635).
The threat posed to monarchs by invasive species is likely to be exacerbated by climate change,
which is expected to facilitate the spread of exotic species (e.g. Dukes and Mooney 1999).
Mortality at Solar Energy Facilities
Monarch butterflies are threatened by mortality from solar arrays, particularly in southern
California and the southwestern United States. In a study of bird mortality at three solar energy
facilities in California, Kagan et al. (2014) documented significant monarch mortality at a solar
site in Ivanpah, California (p. 2). The authors observed “hundreds upon hundreds” of dead
butterflies and concluded that it appears that Ivanpah acts as a “mega-trap” for insects and in
turn, insect-eating birds (p. 2, 20). Some butterfly carcasses were singed. Researchers deduced
that the butterflies were attracted to a brightly lit area around the boiler at the top of facility (p.
20). Based on the large numbers of monarch carcasses observed at the facility, the authors
conclude that solar power towers could have a significant impact on monarch populations in the
desert southwest (p. 21). The threat posed to monarchs from solar facilities will likely increase in
the future as more facilities are constructed.
Electromagnetic Noise
Monarchs may potentially be threatened by electromagnetic noise. Recent research has
demonstrated that monarchs possess an internal magnetic compass, located in their antennae,
which may help guide their migration (Guerra et al. 2014). In a recent paper, Guerra et al. (2014)
note the possibility that electromagnetic noise emitted from various electronic devices could
possibly impair the monarch’s migratory ability:
Taken as a whole, our study reveals another fascinating aspect of monarch butterfly
migratory behaviour. Greater knowledge of the mechanisms underlying the fall migration
may well aid in its preservation, currently threatened by climate change and by the
continuing loss of milkweed and overwintering habitats. Another vulnerability to now
consider is the potential disruption of the magnetic compass in monarchs by humaninduced
electromagnetic noise, which can apparently disrupt geomagnetic orientation in a
migratory bird (Engels et al. 2014) (Guerra et al. 2014).
Electromagnetic noise from AM radio signals and some electronic equipment can disrupt the
magnetic compasses that migratory birds use to navigate (Engels et al. 2014). Human-induced
electromagnetic noise presents a potential threat to the monarch migration and should be further
investigated.
Monarch ESA Petition 107