H. SPECIAL SIGNIFICANCE OF THE SPECIES
The Monarch is unique among North American butterflies in performing an annual two-way migration in vast numbers from one area of the continent to the other. No other North American butterfly, and probably no other insect among the millions of species on earth, performs a similar migration. Much still remains to be learned about how individual Monarchs are able to return each year to overwintering sites and breeding grounds that they have never before seen. The many millions of Monarchs blanketing forested mountain slopes at overwintering sites in Mexico are also a unique phenomenon, and a spectacle of tremendous natural beauty that is reproduced no where else on earth.
The mysterious migration of the Monarch in North America, and the concentration of millions of butterflies into a small region of Mexico each year, appears to have captured the public imagination. Many people with little knowledge of butterflies, or nature in general, recognize the Monarch and know something about its annual migration. The large size, striking appearance and frequent occurrence of the Monarch in cities and gardens have also contributed to making it one of the most familiar North American insects. The initial discovery of the Monarch's overwintering in Mexico was reported in National Geographic Magazine in 1976 and, since that time, the Monarch has received increasing attention from the media. The discovery of the overwintering sites was itself the result of thousands of volunteers tagging Monarchs and reporting Monarch observations to Canadian scientist Fred Urquhart from across Canada and the United States. Recent articles in prominent newspapers such as The Globe and Mail and The New York Times on the plight of the Monarch clearly demonstrate the continued high level of public interest in the fate of this butterfly. A traveling exhibit called "Monarca" was developed by the Canadian Museum of Nature, in cooperation with scientists in Mexico, the United States and Canada, in 1992. This exhibit is currently touring the United States and will eventually reside permanently in Mexico City.
The annual migration of the Monarch in North America has been recognized as an endangered biological phenomenon by various authors (e.g. Malcolm 1993, Brower & Malcolm 1989), and in 1983 the spectacular winter roosts in both Mexico and California were designated as threatened phenomena by the International Union for the Conservation of Nature and Natural Resources (IUCN) in the IUCN Invertebrate Red Data Book (Wells et al. 1983). This was the first such designation in the history of international conservation, and this new status category was created to recognize the fact that the millions of Monarch's migrating and overwintering in North America each year are imperiled, while acknowledging that the species as a whole is not in danger of extinction. The Monarch is indigenous to the New World, and occurs throughout North and South America. In the last 150 years it has also established breeding populations in Australia, a number of Atlantic and Pacific Islands including Hawaii and Bermuda, and recently on the east coast of Spain.
The Monarch is one of the classic examples of butterfly mimicry. Monarch caterpillars ingest toxins (cardenolides) from milkweeds that make them, and the butterflies they develop into, unpalatable to birds and other vertebrates. In contrast to the cryptic coloration of most caterpillars, monarch caterpillars are boldly patterned with striking yellow, black and white stripes which advertise their presence and unpalatability to predators. The bold orange and black pattern of Monarch butterflies similarly acts as a warning to predators and, in laboratory experiments, Blue Jays refuse to eat Monarchs. The Viceroy (Limenitis archippus), whose relatives are purplish-black butterflies with prominent white bands, gains protection from predators by mimicing the Monarch, and has a bold orange and black pattern that closely resembles a Monarch.
I. RECOMMENDATIONS/ MANAGEMENT OPTIONS
1. Consideration should be given to removing milkweeds from provincial noxious weed acts, and de-legislating municipal by-laws for their eradication, while recognizing that in some situations it may still be necessary to actively eliminate milkweeds.
2. The continued availability of healthy populations of milkweeds as larval hostplants for Monarchs would be improved by:
- maintaining wildflower mixes along highway verges and median strips instead of grasses (which require the use of herbicides and repeated mowing).
- encouraging communities to create butterfly gardens and milkweed areas.
- encouraging farmers to cut abandoned fields late in the fall (mid-September to early October) to limit the growth of woody plants.
- encouraging parks (national, provincial and local) that have weedy fields to maintain them through selective cutting and controlled burning.
3. It is important that staging areas where migrating monarchs mass are protected from cutting of critical trees, and from various kinds of human disturbance. Parks with staging areas within their boundaries should be made aware of this fact and encouraged to protect them. Abandoned farmlands adjacent to overnight roosts that sustain an abundance of nectar sources should be included in protected areas.
4. Public awareness and education campaigns highlighting the uniqueness of the Monarch and Canada's role in protecting its annual migration should be encouraged.
5. Canada, as co-signatory to the North American Free Trade Agreement (NAFTA) with Mexico, could work more closely with federal and state governments in Mexico to enhance protection and management of the overwintering sites.
The main reasons for the decline in Monarch populations have been periodic disasters at the Mexican overwintering sites. Some sites may sustain losses of anywhere from 30% to 90% during winter storms (Lincoln Brower personal communication). Alteration of the habitat by man, particularly the opening of forests by logging, has greatly increased the negative effect of winter storms on overwintering Monarchs, and made them more susceptible to predation from birds and mammals. In the past, these disasters have been counterbalanced by the increase in Monarch breeding habitat in eastern North America in abandoned farmland and roadsides. However, the more widespread use of herbicides and insecticides, and the loss of milkweed habitats in this region, threatens to eliminate the ability of the Monarchs to produce the numbers necessary to ensure the survival of the population through the winter. Ways to reverse this trend are discussed in section C and summarized in section I.
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We would like to thank the following individuals who provided information critical to the completion of this report.
Lincoln Brower provided information on the status of the overwintering sites in Mexico. John Lane provided information on the status of the overwintering sites in California.
The following individuals provided information and insight on the status of the Monarch in various regions of Canada: Jon Shepard and Jim Troubridge (British Columbia); Ted Pike and Paul Klassen (the prairies); Alan Wormington (Ontario and Quebec); Tony Thomas, Ken Neil and Bernard Jackson (the maritimes).
Phil Shappert provided information on a variety of topics relating to Monarch biology and distribution.
Funding for this report was provided by the Canadian Wildlife Service and the North American Wetlands Conservation Council.
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