Monarch Butterfly Migration Update: March 18, 1997

Dr. Stephan Buchmann

• Benigno Salazar's Report
• Fernando Romero's Report

	Date	Location
3/05/97	Galveston, TX *
3/09/97	Donna, TX
3/10/97	Austwell, TX (Aransas National Wildlife Refuge)
3/13/97	Kingwood, TX
3/13/97	Hondo, TX * (25 miles west of San Antonio, TX)
3/14/97	Galveston, TX *
3/17/97	Houston,TX

* Thanks to Monarch Watch for providing these sightings!

How to REPORT:
When you see your FIRST monarch this spring, simpy press the Owl Button on the left and fill out a Field Data report. If you have any trouble using this system, send a message to: our feedback form We'd be happy to help you!

Dr. Karen Oberhauser has returned from the Mexican wintering sites and filed a report today. "The trip renewed our sense that the migration of the eastern North American population of monarch butterflies is the most amazing biological phenomenon in the world. Our trip was full of incredible biology, wonderful people, good weather, hard work, and a conviction that it will take many years to fully understand everything we observed." Also conducted research at the time was Dr. Lincoln Brower. This was his 20th trip to the monarch sanctuaries in Mexico! Both scientists worked to answer important questions about monarch biology--and issues related to their conservation. After you read Dr. Oberhauser's report, see if you can answer these Challenge Questions:

Julie Brophy

• Click Here to Read Dr. Oberhauser's Field Report

Challenge Question #6
"What methods did Dr. Brower use to measure the monarchs' use of nectar? Why are the results of this research so important for conservation?"

Challenge Question #7

"What reasons does Dr. Oberhauser give as possible explanations for the apparent increased numbers of monarchs at the Serra Chincua sanctuary this year?"

To respond to these Challenge Questions, please follow the instructions at the end of this report.

Dr. Brower with butterfly he sent on the symbolic migration

Lee Taylor and Shannon Mitchell in Bobcaygeon, Ontario (bob1@knet.flemingc.on.ca) said, "The pine trees serve as an umbrella because they keep rain from pouring down on the butterflies and soaking their wings. They serve as a blanket because they keep the warmth in at night. If they cut the trees down, they put a hole in the blanket and the monarchs will freeze to death."

Students in Kwajalein, Marshall Islands (gses@tcsn.net) also figured the monarchs use pine trees as a blanket for insulation and as an umbrella for shelter from weather. In fact, according to Dr. Brower's research, it is the combination of these 2 factors that is especially important. He discovered that wet butterflies freeze much more easily than do dry butterflies. For example, when butterflies were wet and exposed (not protected by the trees) they froze to death when temperatures dropped to -0.5 C. In contrast, when butterflies were dry and insulated by the pine trees they could withstand temperatures as cold as -8 C. The thinner the forest, the more easily cold temperatures affected the safety of the butterflies. This is one of the most important conservation issues for monarchs in Mexico, because the people who own these forests want to use the trees as a source of income. How do you think the controversy can be resolved?

• Click Here to view other students' answers to Challenge Question # 3

In our last report we asked Challenge Question #4: "How do you think monarchs know when it's time to leave Mexico? (That is, how do you think the butterflies 'tell time'?)"

Students put a lot of thought into this question--and scientists have too! Click Here to see their answers. Students at Fredstrom Elementary in Lincoln, Nebraska explain the sequence of events this way:

"We think that when the days get warmer and longer the butterflies will feel like mating. Once they have mated they will want to come back north to lay eggs. Then they die after they've laid their eggs. Then the cycle begins all over again. Next year they will be migrating back to Mexico. The weather is getting warmer and the sun is out longer, so the days are longer. The flowers start blooming. The monarchs have instincts to leave Mexico and start flying north. The females are mating, then are looking for milkweed. Since they can't fly in cold weather, they must wait until the weather is warmer. They left in the fall because northern winters are too cold." Mrs. Siefert's & Mrs. Thornton's
Fredstrom Elementary School
Lincoln, NE (someone@lps.esu18.k12.ne.us)

Just as the students thought, photoperiod and temperature are the two environmental factors which are believed to trigger renewed activity in the colonies, leading up to their migration. As you have read in field reports from Mexico, by late February and early March activity had increased dramatically. Also during this time the butterflies' sexual organs finally matured. (Remember, these organs had been state of arrested development since late last summer.) How this all works is still a mystery. In fact, it is being studied this very moment! As Dr. Oberhauser's report describes, graduate student Liz Goering is currently using monarchs collected in Mexico to study how mating and access to host plants affect the timing of female diapause termination. ("Diapoause" is the non-reproductive, hibernation-like state in which monarchs overwinter.)

By the way, many students said monarchs know when it's time to leave by "instinct". This is of course true. Any behavior that is not learned can only be explained by instinct. Since these monarchs were not alive last spring, their behavior cannot have been learned. Monarchs know when to leave Mexico in the spring because the information is passed from generation to generation through their genes.

Nature's Clock
One of the most important skills of a migratory animal is its ability to "tell time". Survival depends on being the right place at the right time. To tell time, animals use internal timing mechanisms known as "biological clocks". While the underlying science of these clocks is not fully understood, we do know that animals set their master clocks according to the world's most dependable time-keeper--the sun. The amount of daylight hours (photoperiod) governs the annual rhythm of life throughout the plant and animal kingdoms. Have fun discovering examples of your own biological clock through the following activity:

• Click Here for Classroom Activity, "Tic-Toc Biological Clock".

How to Respond to Today's Challenge Questions:
Please do not answer both questions in one message!

How to Respond to Journey North Monarch Challenge Question # 6

1. Address an e-mail message to: jn-challenge-monarch@learner.org
2. In the Subject Line of your message write: Challenge Question # 6
3. In the body of the message, give your answer to this question:

Challenge Question #6
"What methods did Dr. Brower use to measure the monarchs' use of nectar? Why are the results of this research so important for conservation?"

How to Respond to Journey North Monarch Challenge Question # 7

1. Address an e-mail message to: jn-challenge-monarch@learner.org
2. In the Subject Line of your message write: Challenge Question # 7
3. In the body of the message, give your answer to this question:

Challenge Question #7

"What reasons does Dr. Oberhauser give as possible explanations for the apparent increased numbers of monarchs at the Sierra Chincua sanctuary this year?"

Don't Forget!
Please include the name of your school and your location so we can credit you properly for your answers.

The Next Monarch Migration Update Will be Posted on March 25, 1997.