Monarch Migration Update: March 9, 1999 Today's Report Includes: How Will They Know When it's Time to Go? Winter Monarch Sightings: Map and Data Field Notes from Mexico by Dr. Calvert Field Notes from Eligio Garcia, Intituto Nacional de Ecologia Weather Report from Pedro Ascencio School How Cold is the Monarch's Mexico? Discussion of CQ #5 Discussion of CQ #9: Why More Males Than Females? Discussion of CQ #8: Who Ate These Butterflies? How Many is 56 million? Discussion of CQ #6 How Will They Know When it's Time to Go? Spring is now advancing rapidly across the monarch's breeding grounds in the north. As you read today's report, think about this: Challenge Question # 10 "How do you think the monarchs will know when it's time to leave Mexico?" (To respond to this question, follow the instructions below.) Winter Monarch Sightings: Map and Data Monarch Winter Sightings Before the migration begins each spring, we gather sightings of over-wintering monarchs. There are millions of monarchs in Mexico, but monarchs have also been seen in the following places: Link to Winter Monarch Sightings Field Notes from Mexico by Dr. Calvert The weather remains cool and dry in the Transvocanic belt of Mexico, with temperatures ranging from low 80's (F) during the days and high 40's (F) at night. Clouds usually build up around the mountains in the afternoons, keeping temperatures from climbing. Notwithstanding the coolness, sometime after Eligio's March 1 measurements, the butterflies at Sierra Chincua moved downslope. They now sit at least 300 meters lower than their position in late February, and are strung out along a side drainage that leads from the Mojonera Alta on the high ridge to the main channel of the Barranca Honda. The Chincua colony is quite narrow, maybe 20 meters wide, and has budded--that is, it is split in places into separate colonies. These bud colonies are separated by less than 50 meters, so they are still more or less together. At the nearby el Rosario sanctuary, the movement downward is restricted. Because the forest has been cleared for farming, they cannot descend anymore. (Some conservationists are concerned that the important downslope staging areas are not adequately protected.) The most spectacular behavior occurring during this time in March is "cascading". Literally tens of thousand of butterflies suddenly push off their perches, en masse, and fall downwards. After a fall of 3-5 meters they begin to fly, all in the same direction. The phenomena is absolutely awesome. Butterflies fill the sky at all levels for a period of up to several minutes. Gradually they fly out of the area or land in nearby foliage--with only green spots on the branches where the tens of thousands of butterflies had recently been. Sometimes one cascade will trigger another, resulting in a sequential cascading from numerous branches in the colony. There are times during the over-wintering period that bird predators can also trigger a cascade in a butterfly colony. But the phenomena that we witness in March is orders of magnitude greater than any cascading associated with the presence of birds. The local people believe it is the noise made by people observing the butterflies that causes cascading. However, no one has shown that monarchs can "hear" airborne sound waves. Monarchs do seem to cascade in response to the presence of people, and this is of concern. Challenge Question # 11 "Other than sound or sight, can you think of another way the monarchs might be able to sense that people are present?" (To respond to this question, follow the instructions below.) Field Notes from Eligio Garcia Intituto Nacional de Ecologia Here are Eligio Garcia's measurements of monarch "coverage" at the Sierra Chincua sanctuary: Date Hectares # Trees 03/01/99 2.6 1,180 02/18/99 2.7 1,680 02/11/99 3.8 1,710 02/04/99 2.5 1,500 01/28/99 2.5 1,342 "Realizamos un recorrido por Senguio, Campo Hermoso, Maravatio y Dolores y observamos que muchas mariposas ya estan regresando al norte. Tambien observamos que hay muchas mariposas volando en Cierra Chincua y posiblemente la proxima semana ya se halla ido toda de Sierra Chincua, " said Eligio. "I hope not!", added Bill Calvert. (He's leading a teacher tour to Sierra Chincua next week.) Challenge Question # 12 "What did Eligio observe while driving through Senguio, Campo Hermoso, Maravatio and Dolores--towns to the north of the sanctuary region? How do you explain the decrease in monarch coverage at Sierra Chincua?" (To respond to this question, follow the instructions below.) Weather Report from Pedro Ascencio School Thanks to Profesor Gilberto Salazar and students for monitoring the weather in the Sierra Chincua this season. Imagine having millions of butterflies spend the winter near your schoolyard! Using their data, continue to graph the high, low and average temperatures, and the photoperiod: Fecha Maxima Minima Preciptacion   02/22/99 19.4 5.2 Nada Helada 02/23/99 18.5 6.0 Nada Helada 02/24/99 18.5 7.1 Nada Nada 02/25/99 16.1 7.2 Nada Nada 02/26/99 16.8 7.1 Nada Nada 02/27/99 17.8 6.3 Nada Helada 02/28/99 16.6 5.8 Nada Rocio 03/01/99 18.7 6.7 Nada Helada 03/02/99 17.8 5.8 Nada Helada 03/03/99 18.9 6.2 Nada Nada 03/04/99 18.1 7.2 Nada Nada 03/05/99 17.7 6.9 Nada Helada 03/06/99 20.0 7.2 Nada Rocio Fecha Salida del Sol Puesta del Sol Fotoperiodo 02/12/99 7:12 6:39   02/19/99 7:08 6:42   02/26/99 7:03 6.45   03/04/99 6:58 6:48   03/11/99 6:53 6:50   Challenge Question # 13 "During the past month, how much did the photoperiod increase in the monarch over-wintering region? How does this change in photoperiod compare to your own?" How Cold is the Monarch's Mexico? Discussion of Challenge Question #5 According to data collected by the Pedro Ascencio students during the week of 15 February, wasked which day was the warmest and which night was the coldest? Fourth graders in Mrs. Allen's class in Pueblo, Colorado noted that the warmest day was Thursday at 72 degrees F, and the coldest nights were Monday and Wednesday at 37 degrees F. Each morning the students are also noting whether there is dew ("rocio"), frost ("helado") or none ("nada") present. Why is this important? This region of Mexico is dry tropical forest. Because the monarchs are here during the dry season, sources of water can be scarce. The monarchs drink dew early in the season (Nov/Dec), but as temperatures drop (Jan/Feb), dew is no longer available and the butterflies must fly to open sources such as streams and seeps to drink. By noting whether dew or frost are present, we know if this important source of water is available to the monarchs that day. Why More Males Than Females? Discussion of Challenge Question # 9 Miss Bailey's student at Citrus Elementary School in Vero Beach, FL responded: "Our class thought about why no female monarch butterfly wings were left near a watering hole by a predator, and wrote their guesses in their butterfly journals. Most thought it had something to do with the level of toxic chemicals (cardenolides) in the monarch's body. Amber Pastir thought, "The females protect themselves very well because they maybe eat a lot more milkweed than the males do. So the females might be more poisonous than the males." Evan Brown agreed, "They eat milkweed and get poison from it." (bailey_a@popmail.firn.edu) Toxic cardenolides are an excellent defense mechanism for monarchs. And female monarchs have a 30% higher concentration of the toxins than do males, on average. (Females probably do not eat more milkweed, but their bodies retain more of the chemicals.) As we saw last week, monarch predators have different methods of consuming their prey. According to research by Brower and Fink (1981) orioles vomit after eating only small amounts of the toxin, whereas grosbeaks can ingest larger amounts of the toxin without vomiting. The toxin is stored in the monarch's abdomen in the "cuticle". Looking back at the 2 bird's methods of feeding, notice that the grosbeaks consume the entire abdomen whereas the orioles "unzips" the abdomen and avoids eating the cuticle. Although they have more poison, there are advantages to eating females: Females contain 26% more lipids, so if a predator can tolerate the female's poisons it can benefit from her fat. Who Ate These Butterflies? Discussion of Challenge Question # 8 Ms. Thurber" students in Ferrisburgh, VT: "In picture #1, we can see that the bottom of the butterfly is missing. We are sure that the Black headed grosbeak ate that. Genevieve wonders what a grosbeak looks like. In picture #2, we think that the black-backed oriole ate it. The last picture must be butterflies that were eaten by a black-eared mouse. There were a lot of wings on the ground with all the bodies missing. (lthurfer@pop.k12.vt.us) (Click on photos to enlarge.) #1 #2 #3 How Many is 56 million? Discussion of Challenge Question #6 From Iowa-Grant High School in Livingston, WS (igemsimc@mhtc.net) Nicole and Emily discovered they could give 1 butterfly to each person in each of these states! State # People Wisconsin 5,006,591 Ohio 11,016,358 Minnesota 4,480,034 Michigan 9,436,628 Iowa 2,812,448 Indiana 5,661,800 Illinois 11,631,131 Maryland 4,908,453 TOTAL 56,953,343 How to Respond to Today's Monarch Challenge Questions IMPORTANT: Please answer ONLY ONE question in each e-mail message! 1. Address an e-mail message to: jn-challenge-monarch@learner.org 2. In the Subject Line of your message write: Challenge Question # 10 (or Challenge Question # 11, #12, #13) 3. In the body of EACH message, answer ONE of the questions above. The Next Monarch Migration Update Will Be Posted on March 16, 1999. Copyright 1999 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form