Monarch Butterfly Migration Update: March 14, 2002
Dave Kust to Head North With the Monarchs
March 13, 2002
After Chip Taylor from Monarch Watch stayed with us, he returned home and posted a nice story and several pictures on the web. If you are interested you can find that at:
Monarch Watch Tag Recovery Fund: You Can Help
Please consider a donation to Monarch Watch to help this fund. You?ll not only support the Monarch Watch tagging program, but will also provide needed income for the people in the sanctuary area.
Final Field Notes From Mexico by Dr. Bill Calvert
Final Field Notes from Mexico by Dr. Bill Calvert
March 7, 2002
Butterflies poured down the arroyo and across adjoining fields by the thousands--it was some sight, let me tell you. At times they enveloped the stately agave (century plants) that mark the boundaries of the fields. As the arroyo narrowed the butterfly stream concentrated until there was a flowing river of orange and black filling the arroyo to a depth of 3 meters and entirely in our faces. They were beautiful.
The forest through with the arroyo ran was depauperate. Only a few wolf trees (lone trees) remain. These were festooned with butterfly clusters. As far upward as we could see there was no intact forest in sight.
Also in the arroyo and accompanying our group were four little girls, ages 10-12. They had been instructed by our guide, their grandfather, to stay with gringo stragglers to make sure they did not get lost. Mainly they were curious about us and giggled a lot. One couldn?t help but wonder about their futures. Their fathers had cut the forest that belongs to the community. They had spent their capital. Not much revenue could be got from those forest remnants for at least 20 years, and the supply of water itself was in jeopardy.
March 12, 2002
Witnessing a Predator Feeding Frenzy
At El Rosario we were treated to a predator feeding frenzy that was just amazing. Two brilliant male Black-backed Orioles and two Black-headed Grosbeaks landed on a tree in full view of our observation point. They preceded to take monarchs from the clusters and eat them. They held the butterflies down with one foot and tore off the wings before consuming body parts. We tried hard to observe any ?unzipping? of butterfly abdomens, as orioles are known to do, but were too far away to see it. The birds remained in view for at least 10 minutes and consumed an estimated 20 butterflies. These processes repeated over and over. It was mid-afternoon, and we watched until we were forced to leave. Imagine--these butterflies had survived the entire over-wintering seasonincluding the strongest storm in recorded history--only to be eaten on March 11. They almost made it.
We haven?t witnessed any mass exits. It?s still been cold and they?re not doing much. I think their departure is probably ?stop and go.? They leave when it warms up and stop when it?s cool. At the end of the week we will all go home. All and all, it has been a most interesting and notable year.
Millions of Monarchs Eaten By Predators
To a predator, monarchs clustered by the millions can be a rich source of food and easy prey. For predators who can handle the poisons in the monarchs, that is. When they are caterpillars, monarchs eat milkweeds that contain toxins called "cardenolides." This poison is stored in the adult monarch's abdomen. Because it is poisonous to vertebrates, the toxin is a form of defense for the monarch. Of all the possible predators in the sanctuary area, only 3 vertebrates prey extensively on monarchs--one mouse species and two bird species. In a typical year, upwards of 15% of the entire over-wintering population dies due to predatory activities. When the monarchs arrive in November, not a single butterfly wing is on the ground. By March, the forest floor is peppered with dead butterflies.
Close inspection of a dead butterfly gives a clue as to its predator:
Who Ate These Butterflies?
(To respond to this question, please follow the instructions below.)
Impressions from a Visiting New Jersey Teacher
By Maureen Barrett, Harrington Middle School
Mount Laurel, New Jersey
?It was extremely difficult leaving the El Rosario colony that day. I had just witnessed one of nature?s miracles, something truly spectacular, something truly amazing, something I will never forget.?
Harrington Middle School
Mount Laurel, New Jersey
Regresan las mariposas!
First Report From Migration Pathway in Mexico
The monarchs are on their way! This report just in, from the state of Queretaro, 138 miles (222 km) north of the overwintering sites:
Translations Please! Challenge Question #12
What does this say and what does it tell us about monarch migration?
Migratory Monarchs in Texas?
First Migration Map of Spring, 2002
There?s always uncertainty each spring when monarchs are sighted in places they?ve been spotted during the winter.
It?s about a 500 mile trip from the sanctuaries to the southern tip of Texas. We?ll know more next week as more
monarchs start flooding across the border.
A Careful Look at Monarch Wings
Discussion of Challenge Question #10
First graders in Ferrisburgh, VT noted carefully: ?When it is resting, the butterfly folds its wings, so that the hindwing is covering the forewing. That makes the butterfly smaller and harder to see. The underside of the wing is gray like a piece of bark. The top side is bright orange. The butterfly looks like a piece of bark until it opens its wings. When they are flying or eating, they look like flowers because their wings are so bright and pretty.?
What great observers! Inspect the photo on the left carefully. You are seeing only the undersides of the wings.
Look how brightly colored most of the underside of the forewing is. However, did you notice that the tip of the
forewing is dull? Now look at the photo on the right. When monarchs fold their wings, they cover most of the forewings.
Only the dull tips of the undersides of the forewings show.
How to Respond to Today's Challenge Questions:
1.Address an e-mail message to: firstname.lastname@example.org