10 amazing facts about monarch butterflies and their migration

Monarch butterflies undertake an epic journey every year. Learn more about these amazing insects and their incredible flight for survival.

Bernard Spragg | Public Domain

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With their bright orange-and-black wings, monarch butterflies are some of the most recognizable and beautiful butterflies in America. The colorful adults and striped caterpillars are welcome visitors to backyards and gardens across the country. But did you know that the monarch you spot fluttering outside today might be about to embark on a migratory journey that will take them thousands of miles away? 

Here are 10 fun facts you might not have known about monarch butterflies and their amazing migration:

1. There are two distinct populations of monarch butterflies in the U.S.

You can’t tell the difference by looking at them — they all have the same striking orange wings — but the Eastern and Western populations of monarch butterflies have different lifestyles. 

The Western monarchs breed west of the Rocky Mountains, and spend their winters in southern California. The Eastern monarchs breed in the Great Plains and Canada, and travel all the way to central Mexico to spend the winter!

2. Some monarchs fly for over 3000 miles on their migratory journeys.

Some Eastern monarchs spend their whole lives in the northern U.S. and Canada, enjoying the warm summer weather. But those that emerge from their chrysalis in the late summer or fall know that they can’t survive the colder temperatures to come.

These late-summer monarchs are the ones that embark on an epic trek. Some fly for nearly 3000 miles to make it all the way down to the warm mountains of central Mexico. That’s a long trip for an animal that only weighs as much as a paper clip!

Mike Budd/USFWS | Public Domain

3. Monarchs need one specific kind of plant – milkweed – to survive.

Every monarch butterfly starts its life as a tiny egg glued by its mother to the leaf of a milkweed plant. Once the caterpillars hatch, they get right to work eating and growing. The mother monarch chooses a milkweed plant for her eggs because milkweed is the only thing a monarch caterpillar can eat. 

A single monarch mom can lay up to 500 eggs in her lifetime. That means she needs a lot of milkweed plants in her habitat to ensure all her caterpillars have a safe and healthy place to grow!

4. Monarch wings are covered in scales.

To the naked eye, the colorful wings of a butterfly look like one smooth surface. But under the microscope, it’s clear that what looks like a solid wing is actually covered with structures that look like thousands of tiny scales!

These scale-like structures make a monarch’s wing extremely aerodynamic, helping them to fly. This is why you should try to be careful not to touch the wings of a butterfly too much. Disturbing the wing’s scaly coating makes it harder for the butterfly to maneuver and fly.

5. Monarch butterflies protect themselves with poison.

Those bright orange wings aren’t just for show – they also serve as a warning to birds and other predators that monarchs are dangerous. Their bodies contain toxins from the milkweed plants the caterpillars eat. The milkweed toxins don’t harm the caterpillars, but they still pack a poisonous punch for any animal that tries to eat a monarch butterfly.

This is such an effective strategy that some other species of butterfly have evolved to look similar to monarchs. A predator might think twice about trying to eat any orange-winged butterfly thanks to the monarch’s reputation – even if the mimic isn’t poisonous at all.

6. Monarchs have special senses to help them navigate their long migrations.

Monarchs can use the position of the sun to orient themselves along their long migratory journey. But what do they do when clouds or rain hide the sun? 

It turns out that monarchs have a tiny built-in magnetic compass. By sensing the Earth’s magnetic field, they can find the right direction to travel in any weather.

USFWS | Public Domain

7. Some monarchs can live for over 9 months.

Many bugs have extremely short lifespans. That includes breeding monarchs – those who are born in spring and early summer – which only survive for a handful of weeks. 

But migrating monarchs are different. The generation that makes the long trek to southern overwintering grounds has to survive long enough to get there and back again. These particular monarchs live to be 8-9 months old – a remarkable feat for a fragile butterfly!

8. You can tell male and female monarch butterflies apart by their wings.

It can be hard to get a good look at the details of a monarch butterfly’s small 4-inch wingspan. But if you’re able to examine one closely, it’s actually very easy to tell whether a monarch is male or female. 

All monarchs have stripy, vein-like patterns of black on their orange wings. The key place to look for the difference is in the center of the back pair of wings. Males have a distinctive black spot there; females do not.

A male monarch butterfly, with black spots in the middle of his hind wings. © Eric Alan Isaacson via iNaturalist | CC-BY-4.0
A female monarch butterfly, whose wings are covered in stripes. © Alan Kneidel via iNaturalist | CC-BY-4.0

9. Monarch butterfly populations are declining.

Unfortunately, monarch butterflies are in trouble. The massive flocks of monarchs that once migrated across North America are shrinking. Since the 1990’s, the eastern monarch population has fallen by more than 80%. And according to some estimates, the western monarch population has been hit even harder.

What’s causing monarch populations to plummet? Climate change is one dangerous factor. Butterflies are sensitive to swings in temperature and extreme weather, both of which are becoming more common as our climate shifts. Up to half of the monarchs overwintering in California this past year were wiped out by extreme storms.

Habitat loss is also harming monarchs. Monarch caterpillars need milkweed to eat, and adult monarchs need plenty of flowers to drink nectar from as they migrate. The overuse of weed killers like Roundup can destroy the milkweed plants that monarchs depend on.

10. You can help protect the monarch butterfly from extinction.

There’s a lot we can do to ensure monarch butterflies are safe to make their amazing migration for generations to come. 

One important step we could take is to get monarchs listed as an endangered species in the U.S. If the Biden administration were to list monarch butterflies under the Endangered Species Act, both the butterflies themselves and their habitat would enjoy strengthened protections.

We can also call on governors across the U.S. to plant more milkweed on public lands. Public parks, roadsides, and other areas of green space can make amazing monarch habitats. All we need to do is add milkweed.

You can also help monarchs in your own backyard by planting milkweed at home. By adding milkweed plants to your own garden, you’ll create a healthy habitat for monarchs and all kinds of other pollinators to enjoy.

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