Answers From the Monarch Butterfly Expert
(Back to Monarch Butterfly FAQ)

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

Dr. Karen Oberhauser

From: Amherst, New York

Q: Can butterflies hear sounds?

A: In general, butterflies have very poor hearing. They can often sense sound through veins in their wings, but this has only been studied in a few butterfly species. Larvae can sense sound through small hair-like projections on the surface of their bodies called tactile setae. The setae sense vibrations in the air.

Q. What do Monarchs do in Mexico during the winter? Do they just hibernate, or are they active at times?

A: They are often active, especially when it is warm. When it is cool, they remain quite still in the trees.

Q: Is the endangerment of Monarch butterflies gotten more or less severe?

A: That’s a hard question to answer. For the past two years, monarch numbers as measured by several monitoring programs, have been average or slightly below average. However, the threats to monarchs are getting worse in some places. The trees surrounding their wintering sites in Mexico continue to be cut, and the habitat they use for breeding is continually being developed into suburbs or fields. It is very important that we do everything we can to preserve and create habitat that they require as they breed, migrate and winter.

From: Massapequa, New York

Q: Will weather such as rain, thunderstorms, or snow affect the patterns of a monarch’s migration?

A: All of these forms of precipitation would prevent them from migrating as the precipitation is falling. If it’s cold enough to snow, the monarchs might die.

Q: How will different types of weathering affect the migration patterns of a monarch butterfly?

A: Cold weather will slow them down, as will wind from the south (in the fall). Warm weather or wind from the north will speed them up in the fall. If it’s too hot and dry, they may have trouble finding enough nectar.

Q: Do the monarchs always take the same route to their migration "spot?"

A: Because they’re starting from so many places, there isn’t a single route that monarchs take to their overwintering sites.

From: South Cache 8-9 Center
Hyrum, Utah

Q: How are Eastern and Western monarchs connected? Apparently, there is an Eastern as well as Western species of Monarchs in the United States. Their migration patterns seem to be divided along the Rocky Mountains. Do these two species exclusively migrate to Mexico and Southern California respectively, or do the species ever winter-over in the other site?

A: First, these are not two different species. They are two populations of the same species. There appears to be some movement between the two populations, but they are separated to a large degree.

Q: Why does the Rocky Mountain range act as a separating obstacle for the Eastern and Western Monarch populations? Both species cross other mountain ranges on their way to their winter destinations.

A: While they go over and through other mountain ranges, none are as high or as large as the Rockies. During the time that monarchs are migrating, it’s generally too cold in the Rocky Mountains to allow flight, so they serve as a fairly effective border.

Q: What are the specific differences between the Eastern and Western populations?

A: They can interbreed freely. There may be some differences in their susceptibility to diseases that are more prevalent in one population than the other.

From: Mrs. McCoy's 4th grade Science classes
Alvarado Elementary South
Alvarado, Texas

Q: How are the butterflies able to locate milkweed? We live in Alvarado, TX. Since the monarchs will be arriving so early in spring and the milkweed will still be just sprouting, how are the butterflies able to find it? We saw the milkweed information on the Web site, that showed the milkweed only needed to be an inch or so high for them to lay their eggs on it. How do they find it? Thank you.

A: Monarchs use a combination of visual and chemical cues to find milkweed. Once they land on a plant, they use sensory organs on their feet and heads to tell them if it is a milkweed, and probably the quality of the milkweed.

From: Columbus, Ohio

Q: Do all eggs hatch out before migration or are there some remaining that can hatch out in the spring? I'm wondering if the first generation in the spring is totally reliant on the wintering individuals returning and laying eggs.

A: No, monarch eggs would not survive the winter, at least not in Ohio. The spring population is totally dependent on monarchs migrating from the south.

From: Musselburgh School
Dunedin, New Zealand

Q: How do monarchs make their chrysalis? How do they get out of their chrysalis?

A: The final molt (shedding skin) of the monarch larva results in the chrysalis, so the chrysalis is not so much something that they make as it is something that they turn into.

To emerge, the adult monarch must split open the pupa cuticle. It swallows air through the pupal spiracles. This air travels through the adult’s body to spiracles on the adult thorax, then out these spiracles to the space between the pupal shell and the adult cuticle. If you look closely at an adult ready to eclose, you’ll see this air. The adult then swallows some of this air into its digestive system, causing the body of the monarch to expand. Finally, the cuticle splits along a line of weakness and the adult pulls itself out.

Q: What do the butterflies do all day when they have hatched?

A: They eat, fly, rest at night or when it’s cool, mate, lay eggs, avoid predators, and if they’re in the last generation of the year, migrate to Mexico. They’re pretty busy.

Q: Do monarch butterflies have a nose?

A: They don’t have a nose, but they can still smell. They have nerve cells called chemoreceptors all over their bodies that react to the presence of different chemicals in the air. That’s how our noses work too.

Q: Why do monarch caterpillars and butterflies eat so much food? What flowers do monarch butterflies suck the nectar from?

A: Organisms, including monarch caterpillars and butterflies, eat what they do because they need that much to grow and survive. They get nectar from many flower species.

Q: How long will the butterflies live?

A: The adults live about a month in the summer, or about 8 months if they migrate.

Q: Why do monarchs have four wings?

A. All butterflies and moths have four wings that they use in flight.

From: Tallahassee, Florida

Q: Where do the monarchs that migrate to Florida spend the winter? I know that the largest population winters in Mexico. Do they form huge colonies in Florida?

A: No, they don’t form large colonies in Florida. In many parts of Florida, they continue to breed throughout the winter on milkweed that is available.

From: Bloomington, Illinois

Q: Will wind turbines interrupt monarch migration? We have over a hundred Monarchs that migrate and roost on our farm every year. An energy company is planning on erecting 100, four hundred and five foot tall wind turbines, that turn over 186 mph in our area. Have there been any reports of the migration paths of the Monarch changing or any substantial deaths from these turbines, such as there has been with Raptors in California?

A: I’m not aware of any studies of the impacts of wind turbines on monarchs. I’m well aware of the studies looking at impacts on birds. This is a good example of the difficulty in assessing the costs and benefits of human activities. In my opinion, harnessing energy from the wind will have a net positive on monarchs and many other species, due to the worse effects of other energy-generating activities.

Q: Are there any laws to protect the Monarch in the US?

A: It is illegal to ship monarchs across state lines without a permit. This prevents the mixing of populations that could cause transmission of disease or the mixing of genetic stock. There are no specific laws that protect monarch habitat or individual monarchs.

From: Arlington Heights, Illinois

Q: How does a monarch butterfly know where to find food?

A: Monarchs find food much the same ways that all animals find food. They use their senses to detect it in their environment. They see flowers, and then use senses of touch and taste once they land on the flower to determine the quality and quantity of the nectar that’s available.

From: Rivers Edge Elementary
Fort Pierce, Florida

Q: How are monarchs affected by air pollution?

A: This has not been well-studied. There is some discussion about the effects of ozone pollution on monarchs, especially since milkweed can be damaged by ozone.

Q: Do monarchs have something like a natural clock which they use to know when to migrate?

A: We're not sure exactly what cues the monarchs use to tell them when to migrate. We do know that those that migrate emerge in a state of "reproductive diapause," which means that they won't reproduce at four to six days of age like summer monarchs will. We also know that some combination of information from daylength, temperature, and possibly the age of the plants they are eating triggers this state.

Q: Why are monarchs bolder than other species?

A: I’m not sure what you mean by this. Do you mean why are they brightly colored, or why are they braver? I don’t know that they are braver than other species, and many butterflies are more brightly colored than they are.

From: Spring Woods Middle School
Houston, Texas

Q: Do hummingbirds eat caterpillars? We are preparing a butterfly garden and need to know if hummingbirds eat caterpillars. We found hummingbirds eat small insects and burrow the bark of trees for things such as caterpillars. Is this right? Would it be moth caterpillars and butterflies are okay?

A: Yes, hummingbirds feed their babies caterpillars and other insects. They probably wouldn’t eat monarch caterpillars because they are distasteful due to the milkweed they eat. They might eat other butterfly caterpillars, though. Because butterflies and moths generally lay so many eggs, natural predation is usually not a cause of declining populations, and I wouldn’t worry about hummingbirds in your butterfly garden. They’re beautiful themselves!

From: JC Caruso School
Keansburg, New Jersey

Q: Is it illegal to cut down the oyamel fir trees?

A: No, there are places where oyamels can be cut. They are protected in the Monarch Butterfly Biosphere Reserve.

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

A: They don’t. Females can live up to a month, and they start laying eggs when they’re about four days old. They die when they get old, just like we do.

Q: When a larva is turning into a chrysallis, does it go to the bathroom?

A: No. It empties its gut before it molts.

From: Bay City, Michigan

Q: Do monarchs overwinter in Florida? From the Journey North website, it looks like some monarchs overwintered in Florida this year. Is that true and has this happened before?

A: Yes, they overwinter in Florida often.

Q: Will the monarchs that overwintered in Florida migrate north?

A: We don’t know. It appears that the monarchs that migrate to Florida may just stay there, making this population what is known as a “sink population”; butterflies fly into it from other areas, but don’t return to the other areas.

From: Naples, Florida

Q: Are my Florida monarchs migratory or not? I have been told that monarch butterflies in Southwestern Florida do not migrate, but I definitely had a period when I did not have any monarchs in my butterfly garden and I still do not see them at the scarlet milkweed or lantana they had previously frequented as regular visitors....I do get zebra longwings, sulphurs and a few other regulars at this time.

A: See the answer to the previous question – which is, basically, we really don’t know.

From: California, Kentucky

Q: Years ago (app 1970) my father and I witnessed a gathering of Monarchs in the fall. There were literally thousands of them hanging in chains from the trees in our woods. I don't know how long they had been there but when we went for a camera and returned they were gone. Is it common for Monarchs to gather before migrating? I have never seen this happen again. Thank You, Brenda White

A: You were lucky! They do this – sometimes just stopping once in a particular site, but sometimes stopping in the same site year after year.

From: Rolling Meadows, Illinois

Q: As recently as 2005 there was a severe drought. If many monarchs starved to death because of lack of nectar how many did die, and was the overall monarch population dramatically reduced?

A: The population was low in some parts of the country in 2005, but it was not so bad in other areas. Luckily, parts of the population did fairly well that year, and the population that wintered in Mexico was about average.

From: Bethesda, Maryland

Q: Last summer we found a monarch caterpillar on soil in our front yard nowhere near milkweed. We don't have milkweed anywhere on our property. We transferred the caterpillar to a butterfly weed plant (not known to be a host plant for the monarch caterpillar). The caterpillar survived one week or more, but unfortunately it disappeared and we suspect was eaten by a ground foraging Robin (we have a lot of them on our property). Our question is would the caterpillar have survived to form a chrysalis (and become a butterfly) on the butterfly weed plant or any other plant beside milkweed if there is no milkweed? Also, why did the monarch lay its egg in an area no where near milkweed? Thank you, Judy and David Lieberman

A: Butterfly weed is a species of milkweed, and can be a host for monarch larvae. They usually prefer other species, but will eat butterfly weed. The monarchs that you found may have crawled off the butterfly weed, and may have actually left the plant to pupate when it disappeared.

From: Elizabeth
Journey North

Q: Can you give a specific example that compares monarch metabolism at different temperatures? Or is there a rule of thumb about temperature and insect metabolism like, “For every 10 degrees they burn XX faster.”

A: There are interesting effects of temperature on development that might be useful in teaching, depending on the age of your students. Because insect development is so dependent on temperature, we take both time and temperature into account when we measure the rate at which they develop. They require a certain amount of heat to develop from one stage to another; in theory, the amount of heat required to complete a given organism's development should not vary. This “physiological time” is expressed in units called degree-days (°D). One degree-day is one day (24 hours) with the temperature above the lower developmental threshold of the organism by one degree. Monarchs’ lower developmental threshold is 11.5 degrees C. Myron Zalucki calculated how many degree days it takes monarchs to develop through all larval instars as:

Physiological Time at this Stage (in Degree Days)
1st instar
2nd instar
3rd instar
4th instar
5th instar

Using this information, you could figure out that in 12.5 degree temperatures it would take an egg 45 days to hatch, because every day would only give you one degree-day. In 13.5 degree temperatures, it would take about 22.5 days, since every day is worth two degree-days. You could have your students calculate the temperature needed for them to develop in 4 or 5 days, and do the same for the larval instars or pupa stage.

From: Oregon, Wisconsin

Q: Dear Karen Oberhauser, I am not a student but live in Oregon, Wisconsin. When I was a child in 1970 I remember seeing lots of Monarch butterflies. But over the years I hardly see any. Probably because of the loss of the milkweed that grew wild along the roads and between farm fields. My question: I live in town. If I get seeds for milkweed will they grow in my backyard? What kind of soil is needed?

A: Yes, milkweed should grow in your backyard. Common milkweed grows well in many soil types, but you might want to do some exploring to figure out what species of milkweed would work best for you. Check out this website for great lists, by state, of milkweed.
You’ll need to scroll down to the maps of distributions for different milkweed species.

From: Virginia Living Museum
Newport News, Virginia

Q: I know you are not a geologist, but my question pertains to the Monarch wintering area. Since the over-wintering sites are in the Transvolcanic Mountains of Mexico, are the sanctuaries on the slopes of once-active volcanoes?

A: Yes, this is a volcanic mountain range. While I’m not a geologist, I love geology!

Q: When was the last time geologically that these volcanoes were active?

A: The Paricutin volcano, very near the over-wintering sites, erupted in February of 1943 and buried an entire village. So there is definitely very recent activity in the area.

Q: Are the sites in danger from volcanic eruptions in the foreseeable future?

A: That’s a hard one to predict. Those real geologists are still learning how to predict when volcanoes will erupt!

From: Beauvoir Elementary
Ocean Springs, Mississippi

Q: We are doing a wetlands thematic unit school-wide this year at Beauvoir Elementary. Is there any way that we can set up a webcam meeting with you for our 2nd grade students to participate in? We participated in the Monarch migration project with Journey North and this would be a great culminating experience for our students, and another way to include the use of technology in the classroom. I look forward to your reply.

A: I’m definitely not an expert on wetlands. Additionally, it’s not easy for me to access a webcam here. I would be happy to answer any questions you have about monarchs if your students want to e-mail me. They can also use our FAQ section on the Monarch Lab Web site.