Monarch Butterfly Migration Update: September 30, 2005
Today’s Update Includes
they come!" one person called to the next as the monarchs moved with
the wind across Oklahoma and into Texas this week. A strong cold front
passed on Monday, the winds shifted and blew from the north, and the butterflies
Monarch Wave Moves Down the mid-Atlantic Coast
"Finally, monarchs everywhere on the Virginia shore," wrote Randy Emmit who is counting monarchs every day at his post on Fisherman Island, VA. "I had 82 in 1.5 hours," he said on Wednesday.
While eating lunch with a pal near Roanoke, VA, just a few miles away, Ned Williams was counting monarchs for the first time in his life. "I would estimate about 200 or 300 in a 30 minute period," he said. "Never done this before and didn't have any plans of it. Was just a cool observation at lunch break."
About 200 miles to the north at the Monarch Census site in Cape May, New Jersey, Dick Walton had noted large numbers of monarchs arrive on Tuesday and leave on Wednesday. "These migrants are likely part of the same wave," he said.
Who Saw the Most Monarchs This Week? Migration-rate Math
Follow the link below to a few of this week's most dramatic observations. Read the comments and calculate the migration rate for each. Add your favorites to your own Migration Highlights Map.
How Fast Can Monarchs Migrate?
As monarchs pass over your head on their way to Mexico you may wonder how long their trip will take. Where will the butterflies be in a few hours, days, or weeks? How fast can monarchs migrate? A monarch that was tagged and recaptured on the Atlantic Coast reveals a clue:
Discussion of Challenge Question #4: How Many Hours on a Tank of Fuel?
Last week we asked, "When flying its fastest, using escape flight, for how many hours can a butterfly fly before running out of fuel?" (Assume the butterfly has 140 mg of fuel, and burns 12.7 mg of fuel per hour during escape flight.)
Exactly! This is why monarchs don't flap all the way to Mexico. They can glide for 1,060 hours on the same 140 mg of fuel. The migration patterns we saw this week show how monarchs use the wind to save energy. "The direction and strength of the winds largely determine the progress of the migration," says Dr. Bill Calvert. "Strong fronts tend to 'bunch' monarchs up into discreet pulses. Then, when the winds are northerly and strong, the monarchs fly far."
How to Report Your Observations
Put your monarch news on the map! Please send reports of monarchs flying, feeding, and resting. When you report your observations, include wind speed and direction. For instructions see:
The Next Monarch Migration Update Will Be Posted on October 7, 2005.
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