• Monarch butterfly on swamp milkweed

    A monarch butterfly perched on swamp milkweed. Monarch caterpillars will only eat milkweed, so the plant is vital to the butterfly’s conservation. (Photo: Robert Rutkay/Can Geo Photo Club)

Over the past 20 years, the monarch butterfly population in North America has plummeted. Their increasing scarcity in southern Canada is in large part due to the loss of the insect’s primary breeding habitat and food source, milkweed.

Currently, precious little data exists on milkweed’s distribution in Canada. That’s why from July 28th to August 5th, a coalition of researchers from across the country is encouraging the public to get out into the field, photograph and report sightings of monarch butterflies and milkweed plants.

Led by the Montreal Space for Life Insectarium, Mission Monarch is part of a broader International Monarch Monitoring Blitz that aims to crowdsource valuable information in order to help the butterflies. André-Philippe Drapeau Picard, coordinator of Mission Monarch, spoke to Canadian Geographic about the threats facing monarchs and how Canadians can help.

On threats to the monarch butterfly population

Among the eastern monarch population found in Ontario and Quebec, there are three principal threats. in no particular order.

The first is logging activity in Mexico, which continued legally until the late 1990s, destroying many of the monarchs’ summer habitats. The logging areas in question are now protected, though illegal logging continued unabated until 2015 when Mexican legislation led to the inception of specialized environmental police. Despite this, however, the lasting effects of logging still impact migratory generations of monarchs.

The second is the continuing loss of the monarchs’ sole dietary staple, milkweed, and breeding ground destruction as a result. The habitat range of milkweed spans all three North American nations, though is centred in the northern United States and southern Canada. Mostly concentrated in agricultural landscapes, milkweed extermination is an unintended by-product of attempting to control the spread of more harmful weeds, thereby eliminating the monarch butterfly’s food source in that area.

The third main threat is lethal storms. Significant atmospheric changes during migration season increase mortality rates and make journeys south much more dangerous. In 2016, a snowstorm in Mexico killed millions of monarchs. With global weather patterns only becoming more unpredictable, monarch death tolls during migration seasons will climb.

On the monarch’s amazing migration

Monarch butterflies make a three-month, nearly-4,000-kilometre trip from Canada to Mexico, high in the sky while using wind currents for speed. A few times during the trip, they will stop to drink milkweed nectar and refuel. A given year’s migratory generation of monarchs leaves most of Canada in the fall, though in Ontario and Quebec, they leave in September. These monarchs can live up to seven months longer than their parents, and are born with incomplete reproductive organs so they cannot breed until their return home the next spring.

On how to find and identify milkweed

Milkweeds are usually found in open habitats such as roadsides, open meadows and fields. Common and butterfly milkweed can grow in many different soils. Swamp milkweed can be found in wetlands.

Milkweed pods generally resemble elongated pickles with wrinkled surfaces. In the fall, the pods dry, crack open, and release new seeds. The seeds are attached to white threads and resemble cotton balls. Common milkweed has white, leathery leaves with pink flowers at the top of the plant, and a very pleasant aroma. The plant contains latex; if you tear a leaf off, and a white liquid comes out, you have very likely found milkweed!

We have multiple useful tools on the Mission Monarch website, one of which is a milkweed identification guide. In addition, we have an identification guide for butterflies and species that may be confused with the monarch, both at the caterpillar and adult stages. 

On how the public can contribute to monarch butterfly habitat surveying and preservation

On a practical level, you can plant milkweed in suitable areas to help attract monarchs. In order to protect the species, we need to protect its breeding habitats. We have an idea of monarchs’ distribution across Canada, but we need fairly precise knowledge on the concentration of milkweed and where the majority of breeding occurs.

We also encourage people to further educate themselves about monarch butterflies in North America. In Canada, Mission Monarch is partnering with the David Suzuki Foundation, whose Monarch Manifesto encourages citizens to be more mindful of their impact on monarch habitats. Mission Monarch is currently the only Canadian citizen science project dedicated to monarch conservation and one in a long line of future initiatives we will continue pushing to ensure a better environment where they can thrive again.