How High do Monarch Butterflies Fly During Fall Migration?

Contributed by Dr. Bill Calvert

Q. What's the highest you've ever known monarchs to fly?
A. Glider pilots have reported monarchs flying as high as eleven thousand feet.

Q. Why do they fly at such high altitudes?
A. At increasingly higher altitudes wind speed increases rapidly. So if the winds are going in the right direction, it pays monarchs to thermal upward.

Q. Why don't monarchs always fly that high?
A. The height monarchs fly depends on which way the wind is blowing. When winds are from the south, monarchs fly very low. Or, if the winds are strong enough, they don't fly at all. They wait patiently in low areas with lots of trees (if available) for the winds to turn around. During these times, they mysteriously accumulate. This is when they form their gigantic roosts and people are dazzled by large curtains of hanging butterflies at night and early morning.

When the winds turn around the story is very different. During a typical morning with correct winds, monarchs will burst out of their roosts after they have warmed themselves enough to fly. Remember they are cold blooded creatures (poikilotherms in scientific lingo) and must depend on sunlight (radiation) to warm their flight muscles. Once they leave the roost they may fly to a point in full sun where they bask some more or they may search for a morning thermal, and ride the rising air upward, twisting and turning like a feather caught in the wind. For more information about wind and migration see:

Q. Do they go as high as the clouds?
A. If they fly at 11,000 feet they could certainly be above some clouds. Clouds help to spot monarchs. That is, you can see a monarch against a cloud much more easily than you can see one in clear air. If you saw a group of them against a cloud and knew the height at which clouds began that day, you would at least know the upper limit for the group you were observing.

Q. Do monarchs go higher than the naked eye can see?
A. If the thermals are strong they may rise until we can see them no more. Normally a group of migrants consists of butterflies flying a many levels. Some will be within 100 feet of the ground. Others will rise so high that they disappear from binocular view.

Q. At what altitude do they disappear from view?
A. You could do a simple experiment to see how far a butterfly is when it disappears from view. Find a dead monarch or make one from orange colored cardboard. It has to be the same size and approximate color as a real monarch. Attach it to a highway sign on a little used road or a playground if there is a large one nearby. Walk away from the sign until you can no longer see the monarch, and then measure the distance from you to the sign. You may have to get a parent to drive to measure the tens of a mile. Try the same thing with binoculars.

Q. How much of their migration time do monarchs spend high in the sky, and how much time down where they can be seen?
A. It's hard to say with certainty, but monarchs seem to fly at least 3/4 of a day, say from 8:30 to 5:30 during days with good winds. Sometimes they will stay up until just about dark. In deserts they come down much earlier, perhaps as early as noon. It's not known what brings them down. But the opportunity to nectar and too much heat may be factors.

Try This! Journaling Questions

  • At what distance do monarchs disappear from view? Try the experiment Dr. Calvert suggests and send us your results!
  • If glider pilots have seen monarchs flying 11,000 feet in the air, how high is that in miles? In kilometers?
  • If surface winds were 20 mph and winds at 3000 feet were 40 mph blowing from the northwest, and a monarch rode thermal up to 3000 feet, how far could a monarch fly in a day?

National Science Education Standards

Life Science
The behavior of individual organisms is influenced by internal cues (such as hunger) and by external cues (such as a change in the environment). (K-4)

Regulation of an organism's internal environment involves sensing the internal environment and changing physiological activities to keep conditions within range required to survive. (5-8)

Behavior is one kind of response an organism can make to an internal or environmental stimulus. (5-8)

Earth Science
Weather changes from day to day and over the seasons. Weather can be described by measurable quantities, such as temperature, wind direction and speed, and precipitation. (K-4)

National Math Standards

Numbers and Operations
Compute fluently and make reasonable estimates.

Measurement
Understand measurable attributes of objects and the units, systems, and processes of measurement.

Problem Solving
Solve problems that arise in mathematics and in other contexts.

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