Where Have All the Monarchs Gone?

Monarch butterflies are a tropical species, and like other tropical insects, they cannot survive the winters of Canada and much of the United States. This is why monarchs leave Canada to make an astounding, cross-continental journey to the tropics every fall, returning to our neck of the woods each spring.

Unique biological phenomenon

Although they are the most iconic of the butterflies in North America, monarchs are actually found all over the world. However, it is only the monarchs of North America that make an annual migration from as far north as Canada into as far south as Mexico, and it is one reason this migration event is considered such a unique biological phenomenon.

Although globally the monarch is not considered to be endangered, in recent years fewer and fewer monarchs have been observed in North America. The population size of these monarchs has been in decline over the last 10 years, and as this particular monarch population continues its free fall, it is the loss of this unique migration that is of conservation concern.

Monarchs in Canada

North America has two populations of monarch butterflies, one found on each side of the Rockies. In Canada, the eastern population of monarchs occur from Newfoundland to Alberta, and migrate to Mexico to overwinter.

The eastern population constitutes 90 percent of Canada’s monarch population. The significantly smaller western population is found west of the Rockies and overwinters along the coast of California.

Although a much larger proportion of monarchs visit and breed in the United States than in Canada, monarchs are regular visitors to our part of the continent, and protecting their habitat in Canada has a great deal of merit. Furthermore, it is likely that their breeding habitat in Canada could become increasingly important as climate change progresses and alters the range of the monarch butterfly further into Canada.

Population free fall

Monarchs are highly susceptible to extreme weather, and large numbers can be easily wiped out by a single weather event. For example, in 2002 a winter storm killed about 500 million monarchs—this is about 14 times the size of the current (December 2013) population.

Although the size of the monarch population in North America naturally fluctuates wildly from year to year, the current population estimate is the lowest since recording began more than two decades ago. Overall, it is estimated the North American monarch population has declined by as much as 90 percent over the last two decades, and there is strong evidence to suggest the reasons for this decline are human caused.

Threats to the monarch population

Logging practices

Initially it was believed that logging practices in the monarch’s overwintering region—Mexico—was the main threat to this butterfly. However, it has since become more apparent that the decline is also caused by lost breeding habitat, specifically milkweed habitat, in Canada and the United States.

Farming practices

Milkweed leaves are the only food monarch caterpillars can eat, and lucky for them there are about 115 different species of milkweeds in North America that they can choose from. Unfortunately, milkweeds are also commonly found as a weed on farmlands, and recent farming practices—specifically, the increasing reliance on herbicides and movement away from tilling—are highly efficient at killing milkweeds.

Invasive species

Dog-strangling vine, another threat to monarch butterflies, is an invasive plant that closely resembles milkweed leaves, which can confuse monarch females that are ready to lay eggs. Once caterpillars hatch from eggs laid on dog-strangling vine, they die as they do not have access to a food source.

Help save the monarch

Many of us take pleasure in observing monarchs, among other butterflies. We can all do our small part by lending monarch butterflies a helping hand.

Plant a pollinator garden

Why not consider planting a pollinator-friendly garden this year? In addition to attracting monarchs that may lay eggs or come for nectar, you may attract other butterflies and even bees, who are also in need of some tender loving care.

Create a monarch waystation

Monarch waystations are habitats that provide monarch butterflies with much-needed resources to help them along, especially during migration time. These would include milkweed plants for breeding as well as flowers that provide nectar for adults.

A monarch waystation habitat can be created anywhere:

• in your home or community garden
• at your school, college, or university
• alongside roads and highways
• in parks and other green spaces
• in cities, suburbs, or rural areas

Consider becoming a citizen scientist

You don’t have to wear a white lab coat to participate in a science project. Many naturalist groups conduct monarch counts during the spring and fall. These counts are essential to determine how healthy and numerous the monarch population is in any given year. Contact your local naturalist group to find out if they conduct an annual monarch count. If not, consider initiating one!

Monarchs are lucky they are so charismatic. Our fascination with this species may well be part and parcel of any success we have in protecting them. 

Learn more about the monarch butterfly, and other butterflies!

These resources are also gateways into the exciting world of wildlife conservation and citizen science.

• Journey North - journeynorth.org
• Monarch Joint Venture - monarchjointventure.org
• Monarch Teacher Network of Canada - monarchteacher.ca
• Monarch Watch - monarchwatch.org

Timeline of monarch decline and conservation efforts across the continent

Plant a butterfly garden!

Location

A sunny area sheltered from wind makes an ideal location for your butterfly garden. Place a few stones in or around your garden; they will absorb the sun’s heat, which will attract butterflies, particularly after a cold night.

What to plant?

If you wish to attract monarch butterflies (and we hope you do!), don’t forget to plant milkweed. And make sure you clear away any dog-strangling vine (Vincetoxicum rossicum) that is present on your property.

All butterflies like flowers that provide good sources of nectar. Some particular favourites include

• asters (Aster spp.)
• dill (Anethum graveolens)
• butterfly bush (Buddleja davidii)
• Queen Anne’s lace (Daucus carota)
• Joe-Pye weed and related species (Eupatorium spp.)
• fennel (Foeniculum vulgare)
• parsley (Petroselinum crispum)
• goldenrods (Solidago spp.)