To most Canadians the monarch butterfly (Danaus plexippus) is a sure sign of summer. Yet catching a glimpse of this seasonal icon along roadsides and fields is becoming an increasingly rare event.
While not at immediate risk of extinction, monarch populations are now being monitored for signs of trouble. The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) listed the monarch butterfly as a species of “special concern” in 1997.
Under the Species at Risk Act (SARA) the Monarch is listed as a species of “Special Concern”. This type of designation only requires that a management plan be prepared but does not offer the Monarch adequate protection against its destruction, harassment, capture, or the destruction of its habitat. However, Canada and Mexico have made a joint declaration to nominate sites within both countries as part of an International Network of Monarch Butterfly Reserves. Three areas along the north shore of lakes Ontario and Erie have been designated as reserves—Long Point National Wildlife Area, Point Pelee National Park, and the Prince Edward Point National Wildlife Area. This guide is intended for use by residents of these areas and beyond who wish to help create natural corridors for monarch staging areas and migration beyond the network’s boundaries.
This guide provides background information on the monarch butterfly, suggestions and tips on native butterfly gardening, and descriptions of specific plant species that are necessary for the monarch’s survival. By using this guide, not only will you attract these black-and-orange jewels for your enjoyment, but you will also be protecting local ecosystems and encouraging biodiversity.
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|The viceroy butterfly (Limenitis archippus) looks like the monarch, but is smaller and has a curved vein that parallels the hind wing. By mimicking the monarch it probably fools predators into thinking it too has cardenolides as a poisonous defence.
The monarch butterfly is also known as the “milkweed butterfly” because milkweed is the only plant monarch larvae can eat. The female butterfly lays about 400 little yellow eggs on the underside of milkweed leaves. The eggs develop in about two weeks, their colour turning from yellow to light grey. Once the larvae or caterpillars hatch they begin an eating frenzy, consuming the plant’s leaves, flowers and sometimes seed pods. The larvae have yellow, black and off-white rings. The insect completes all of its growing in this stage, which takes nine to 14 days under normal summer temperatures. Once grown the larvae attach themselves to a twig. Hanging upside down by their tail they shed their outer skin and transform into a pupa or chrysalis in a matter of hours. The pupa resembles a waxy, jade-coloured vase adorned with golden spots. After about two weeks the adult butterfly emerges and takes a couple of hours to dry its wings before taking its first flight. The adult male monarch is bright orange with a black pheromone scent patch in the middle of the hind wing. The female is dull orange or brown with more noticeable scaled black veins. Adults subsist largely on nectar produced from fall wildflowers.
|As well as containing nutritional value, milkweed plants also contain a bitter heart poison called cardenolides that is stored in the wings and abdomen of monarchs throughout most of their life cycle. This poison provides some protection from predation.
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The monarchs that appear in southern Canada are not the same individuals that migrated south the season before—they are the latter’s offspring, or in some cases offspring several generations down the line. Monarchs are one of only a few butterfly species in North America that migrate.
|In Canada there are two distinct populations of monarchs: a large, widely distributed eastern population found east of the Rockies, and a second smaller western population found only in central British Columbia. The breeding range in Canada closely reflects the distribution of milkweed species.
Until 1975 no one knew exactly where the monarch’s wintering grounds were located. A tagging project began in the 1930s and after thousands of tagged butterflies and several decades of work, the overwintering roosts in the mountains of central Mexico were finally discovered. Adults that hatch in mid-summer in Ontario will fly 3,000 kilometres (travelling about 50 kilometres a day), reaching the Michoacan state of central Mexico by October. Here they congregate by the millions in a Canadian-type northern fir forest. The forest provides cover as the monarchs drape themselves from the fir trees in the millions. This behaviour protects them from temperature extremes and dryness.
|Unlike the eastern population of monarchs that migrate to Mexico, the smaller western population migrates to wintering sites in southern California.
In mid-March the monarchs leave their wintering grounds and begin their northward journey. They may only get as far as Texas where they will breed. This process of breeding and flying north continues through several generations until the third or fourth generation reaches Ontario in early June.
There are several theories about how monarchs that have never been to Mexico find the traditional roost the following fall. They may orient themselves based on the sun’s position or the earth’s magnetic field, by landscape features, or by a combination of these. Another theory claims that because of their small body size, monarch migration may be influenced by weather and climate conditions, such as wind. Tagging programs continue in an attempt to learn more about this migratory phenomenon.
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Threats include the use of pesticides and herbicides, the loss of native plant species and the propagation of invasive non-native plant species, and more recently, the spread of genetically modified pollen (some of which are equipped with DNA programmed to kill non-specific butterfly and moth larvae). However, because millions of monarchs congregate in one somewhat localized area in Mexico, the largest threat facing this species at present is the destruction of their wintering grounds. The fir forest from which they seek protection is being cut down by large logging companies and burned by local communities for agricultural purposes. As a result researchers are seeing monarch colonies breaking up earlier and exposing themselves to late frosts in the United States and Canada.
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How to help
Improve and protect monarch habitat in your area by planting native host species, such as those included in this guide. Native host species are important for the following reasons:
- Native plants have adapted to local soil and climate conditions so they do not need watering or chemical fertilizers and pesticides to thrive.
- Many native species thrive in poor soil.
- Native species have evolved with the local bird, mammal, butterfly and insect populations and therefore provide them with food and habitat.
- Growing native species improves biodiversity and creates a local seed source.
- Planting native species connects existing green spaces, which provide migration corridors for urban wildlife, like the International Network for Monarch Butterfly Reserves.
Learn how to plant your own butterfly garden!
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