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Ask the Expert

Answers From the Monarch Butterfly Expert

Special thanks to Dr. Karen Oberhauser for providing her time and expertise in responding to your questions.

If you'd like to help Dr. Oberhauser answer her own questions about monarchs, read on. Volunteers are needed this season to help monitor monarch reproduction throughout their breeding range. You can read more about this study on the Monarch Watch WWW at:

Grove Elementary

Q: What does Mariposa mean? How do the Monarch butterflies know that Arizona is a northerly direction?

A: Mariposa means butterfly in Spanish.

Most scientists think that butterflies use the position of the sun in the sky as a kind of compass that allows them to determine which way is north. They may use other cues, such as the earth's magnetic field, but we have a lot to learn about monarchs' sense of direction.


Q: How do Monarchs keep dry if it rains, how do they dry their wings and
what happens to them if they get wet?
Taylor@Sunderland Elementary Grade 2, Massachusetts

A: Monarchs do not need to stay completely dry. If they get wet, they remain in the same place until the water evaporates off their body. They can't fly when they are very wet, however, because it makes them so much heavier. When it rains, butterflies in my experimental cages hold onto the sides of the cages until it stops raining and they dry off. In the wild, they hold onto trees or bushes. If wet monarchs get knocked off these perches, they sometimes get stuck on the ground.

Q: How do monarchs breathe? Jeffrey@Sunderland Elementary Grade 2,

A: Monarchs breathe through tiny opening on the sides of their bodies called spiracles. These spiracles are connected to a series of tubes called trachea that carry oxygen through their bodies. They don't have lungs like you and I do.

Q: How many Monarchs travel together at the same time and how do they travel such far distances? Lydia@Sunderland Elementary Grade 2, Massachusetts

A: The number of monarchs that travel together varies in different places and at different times. We aren't sure if they actually seek each other out and fly together on purpose, or if they just happen to be together because they're all going to the same place. They are able to travel such far distances by flying very efficiently. They take advantage of air currents and actually soar, like many birds do. This takes much less energy than flapping their wings all the time.

From: IOWA
McKinstry Elementary

Q: If the monarch butterfly is toxic to the two preditor birds, what effect does the toxins have on the mice preditors?

A: The two bird species that eat monarchs in the Mexican overwintering colonies have probably evolved to be able to tolerate the toxins, and this is apparently true of the mice as well. Of five species of mice that are known to be common around the overwintering sites in Mexico, only one eats monarchs. In two different summers, mice have eaten monarch pupae that were in cages that I was keeping outside. I don't know if this made the mice sick, however, and as far as I know, no one has studied whether these particular mice are important predators of monarchs.

Q: Approximately how long does it take preditors bodies to eliminate/reduce the toxin levels to a safe level or to where they can eat again?

A: This would vary a lot with the size and species of the predator, and hasn't actually been studied very much. We do know that some predators seem to be able to tolerate the toxins in monarchs with very few problems.

Pigeon River Elem.

Q: Do monarch butterflies have brains?

A: Yes, they do. All insects have brains. Just like our brains, their brains receive messages from the rest of the body, and send messages to the muscles and other organs in the body. They are relatively smaller than our brains, though.

Hudson Falls Middle School

Q: What is the name of the poison on the monarch butterfly's wing and how potent is it? Melissa Rivers Ms. Lobb's period 5 class Hudson Falls Middle School

A: Monarchs sequester chemicals called cardenolides, or cardiac glycosides. These are poisonous to most vertebrates (animals with backbones), but they may not be poisonous to invertebrates. The potency depends on the amount of toxin that the predator eats, and what the predator is.

Q: Why do monarch's migrate and not hibernate? Deanna Jones Ms. Lobb's period 5 class Hudson Falls Middle School Hudson Falls

A: This is a hard question, because we need to know the evolutionary history of monarchs. We are quite sure that the ancestors of monarchs were tropical butterflies that could not survive long periods of very cold weather. When monarchs moved into areas that had cold winters (like Hudson Falls and St. Paul!), they never evolved the ability to tolerate these winters, and need to migrate to warmer locations.

Q: If monarchs did hibernate, how much food would they have to eat in order to survive the winter? Deanna Jones Ms. Lobb's period 5 class Hudson Falls Middle School Hudson Falls

A: Since monarchs (and other insects) are cold-blooded, they do not use much energy when they are in a cool environment. Butterflies that hibernate don't need to store as much fat as warm-blooded animals.

Grove Elementary

Q: Why didn't the Monarchs go to Arizona when they left Mexico rather than going to Texas? Is there any difference between chrysalid and a chrysalis?

A: Some may go to Arizona, but if you look at map that shows mountain ranges, you will see that there are lots of mountains between the overwintering sites and Arizona. It would be very hard for the monarchs to fly over these mountains.

Chrysalid and chrysalis are synonyms.

Griswold Middle School

Q: Where does the Monarch Butterfly fit in the food web is it is considered poisonous by its predators due to the fact that it eats milkweed?

A: Good question! You must be taking an ecology class, or have an excellent science teacher! It turns out that most biologists have studied the predators of adult monarchs, and not the larvae. Many insects, spiders, and other invertebrates eat the larvae, so monarchs are like other herbivores; they eat plants, and are in turn eaten by predators.

Lake Crystal Elementary

Q: Do you know any address I could write to find out about the monarch? How small is the monarch? What class does the monarch belong to?

A: You can write to me! You can also look at the Monarch Watch website ( or read many books about monarchs. You could ask your teacher if she or he has a copy of the Monarchs in the Classroom curriculum, which contains most of the information that I'm including in these answers.

Monarchs weigh about half a gram, and have bodies that are about 10 cm wide (including their wings). They are the class Insecta, which includes all insects.

Q: Why do the butterflies die after they lay their eggs?

A: They don't really. Monarchs live as adults for anywhere from 2 to 6 weeks, and females lay eggs and males mate throughout most of this period (assuming that they aren't in the generation that migrates). They die when they get "old", just like people do. In many cases, females still have eggs in their bodies when they die, so they don't always get a chance to lay all of their eggs.

Karen Oberhauser
University of Minnesota
Department of Ecology,
Evolution and Behavior

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