Monarch Migration Update: March 9, 1999 Today's Report Includes:
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:
(To respond to this question, follow the instructions below.) Winter Monarch Sightings: Map and Data
Field Notes from Mexico by Dr. Calvert ![]() ![]() ![]() 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.
(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:
"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.)
(To respond to this question, follow the instructions below.) Weather Report from Pedro Ascencio School
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. 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!
How to Respond to Today's Monarch Challenge Questions
1. Address an e-mail message to: jn-challenge-monarch@learner.org
Copyright 1999 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form
|