Monarch butterfly

Sault Ste. Marie Canal National Historic Site

Monarch butterflies are one of the most recognizable species in Canada. While they have been spotted on almost every continent in the world and colonies have established in some tropical climates, the migratory population of North America is a unique natural phenomena.

During the months of June to August, the Sault Ste. Marie Canal is a temporary home for many monarchs who use our site to lay eggs of the next generation of Monarchs that will eventually fly south for the winter. This generation of Monarchs travels over 4000km south to Mexico! It takes Monarchs about 2 months to make this journey. 

Life Story of the Monarch Butterfly

Life begins as a tiny egg laid on the leaf of a milkweed plant. It develops for 4-5 days before it hatches a tiny caterpillar, so small it’s hard to see with the naked eye. Caterpillars spend about 2 weeks munching away on milkweed leaves growing from microscopic to 5 cm in length. The toxins in the milkweed plant are incorporated into the body of the monarch caterpillar and later the adult, making them taste terrible and preventing many predators, like birds, from eating them.

When large enough, the caterpillar will hang from a leaf in a “j formation” and begin the magical process of becoming a chrysalis. In this stage, watch for the antennae to twist into a corkscrew – the skin will then split, revealing a writhing green mass which soon hardens to form a chrysalis. In 12 to 16 days, the outside of the chrysalis will change from green to clear and the butterfly will emerge shortly thereafter. After pumping fluid into the wings and drying, the adult will be ready to fly off and start the process all over again.

Most adult monarchs live for about a month, during which they will mate and lay eggs. One special generation, a generation that is born here at the Sault Ste. Marie Canal, will live for more than 6 months. Monarchs that emerge in late August and September don’t have the urge to reproduce – instead, they migrate. All energy is put into creating fat stores allowing the butterflies to make the incredible journey over 4000 kilometres to a mountainous forest in central Mexico. From late August to mid-October many monarchs migrate south through Ontario. The Great Lakes act as a barrier and the butterflies choose the shortest points to cross the lakes.

Mystery of Monarch Migration

For centuries there have been stories about migrating monarchs, but until 1975, no one put all the pieces of the puzzle together to determine where the butterflies were going. Dr. Fred Urquhart (University of Toronto) and Norah Urquhart began tagging monarch butterflies. As the tags were returned, they were able to map the route the butterflies took, leading them to the cool mountains in central Mexico. They discovered large roosts of millions of butterflies – so many that the branches of the evergreen trees would bough under their weight. These roosts house all of the migratory monarchs east of the Rockies; a similar location on the Baja Peninsula is the overwintering ground for the western population.

Continued study has shown that the butterflies rest on the trees most of the time, flying and feeding only on the warmest days. As the days grow longer through the winter, they become more active and by March they start the journey north, mating and laying eggs along the way. Their offspring will arrive at the Sault Ste. Marie Canal in late spring, to start the process all over again.

Monarch Conservation

Ascelepias syriaca

Over the last decade, scientists have seen dramatic drops in the eastern Monarch population. Many different factors, including habitats loss and extreme weather have impacted the monarch population. Currently, Canada, the United States, and Mexico are working together to protect this amazing natural phenomena.

What is the site doing to help?

The Sault Ste. Marie Canal is actively protecting the milkweed plants that grow here. Milkweed is the only plant that Monarch larvae can eat, and so protecting the areas it grows from being cut down helps to maintain the Monarch population.

What can you do to help?

Plant a butterfly garden with native plants.

Butterflies prefer groupings of flowers, with trees or shrubs nearby to provide shelter from excessive heat and wind. Since butterflies are attracted to many drought tolerant perennial wildflowers, a butterfly garden offers a great, low maintenance alternative to traditional gardens.

·         Select a site that provides sunny exposure, good drainage and some nearby trees or shrubs for shelter.

·         Remove the layer of turf and work up the soil to a depth of at least 20 cm.

·         Amend the soil with compost or other organic material.

·         Plant a variety of native species, preferably those that offer different flowering times throughout the year. Space plants according to their respective height and width when mature.

·         Plant milkweed which provides habitat for monarch caterpillars.

·         Plant native species that flower into the fall to provide nectar for migrating butterflies such as black-eyed susan, joe-pye-weed, Canada goldenrod, New England aster, and large-leaved aster.

·         Water immediately.

·         Provide aftercare in the form of additional watering and weeding.

To find more detailed information about your eco-region, consult with Pollinator Partnership Canada.

Become a citizen scientist

Parks Canada researchers and Resource Conservation team members need your help to contribute valuable biodiversity data about the Sault Ste. Marie Canal.  You can help by becoming a citizen scientist and sharing your observations on our iNaturalist project. Take a photo of a plant or animal you see at the canal and share this information with scientists and nature enthusiasts alike.

Additionally, you can conduct a mission using the Mission Monarch toolkit to help document the monarch habitat at the Sault Ste. Marie Canal. A mission consists of finding milkweed, looking for and documenting the presence of monarchs and then submitting the data. 

More information and resources are available at the visitor centre.

Date modified :