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Migration
Update: February 5, 2009 |
Please
Report
Winter Sightings! >> |
Today's
Report Includes:
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Why
do these trees look orange? >>
Picture of the week
by Dr. Lincoln Brower
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Welcome
to Journey North! |
Welcome
to our 16th season of tracking the monarch's spring migration. When
Journey North begins every February, the monarchs are at their winter
home in Mexico. As we wait for their migration to begin in March, our
weekly updates focus on the theme of survival.
The monarch's ability to survive the winter in Mexico is as remarkable
as their spectacular migration. Today's report explores an important
conservation question: How many monarchs are in Mexico this winter?
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Monarch
butterflies east of the Rocky Mountains fly to Mexico. >>
They gather together on only twelve mountain top sites. Find them!
>> |
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How Many Monarchs in Mexico This Year? |
Scientists
Measured the Population in December
The
twelve major monarch butterfly sanctuaries in Mexico are measured every
winter in December. These yearly measurements give scientists a chance
to estimate the size of the entire overwintering population.
Everyone
Expected a Small Population
Last
fall at the end of the migration we asked you to predict
how large this winter's population in Mexico would be. People across the
monarch's range had reported low numbers during fall migration. For example,
only half as many overnight roosts were reported in fall 2008 as fall
2007. Monarchs were scarce during the summer breeding season, too. Based
on observations like these Dr. Chip Taylor of Monarch Watch predicted
the population would measure less than 5 hectares, and perhaps as small
as 3-4 hectares. Many people returned unused tags "along with short
notes lamenting the lack of monarchs this past fall and requests for an
explanation as to why the fall 2008 monarch population was so low,"
he commented in Monarch
Watch Blog.
So what did the scientists in Mexico find?
A
Surprise!
Last week the scientists announced good news. This year's population is
not as small as predicted. In fact, it is slightly larger than
last year's.
Area
Covered by Butterflies |
Last
year
4.61 hectares* |
This
year
5.06
hectares* |
*One
hectare equals 2.47 acres. |
Mexican
biologist Eduardo Salinas-Rendon led the team that measured the monarch
population this winter.
.
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How
does this year compare? >> |
Where are the butterflies? >> |
Compare this year's population
to those in the past 14 years. How
has the size of the monarch population changed during your lifetime?
>>
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Nearly
75% of the monarchs are at just two of the 12 wintering
sites. Find
them on the map. What does this mean for conservation? >>
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How
do scientists measure the colonies? >> |
Scientists
want to know if we are doing a good job protecting monarchs. Because the
monarchs in Mexico have come from across eastern North America, the winter
measurements have extra meaning. Scientists watch these numbers carefully
and try to understand what causes changes in the size of the monarch population.
Today,
see how the scientists measure the monarch colonies, and try making some
measurements yourself. >> |
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Journal
Page: How
many millions of monarch butterflies? |
How many
millions of monarch butterflies are in a monarch colony? For almost twenty
years scientists used an estimate of 10 million monarchs per hectare.
Then something happened.
- Read
the Story!
Find out what caused scientists to raise their estimate to as high as
50 million monarchs per hectare. >>
- Write
in Your Journal: Estimate how many millions of monarch butterflies
are in Mexico this winter. >>
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News
from Mexico: A Report from the
Field >>
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Thanks to Susan
Meyers and Kim Baily of "Monarchs Across Georgia" for sending
this report directly from Mexico. They are leading a trip for teachers
and visited two monarch sanctuaries this week, Sierra Chincua and El Rosario.
As
you read: Look carefully for words that describe the
monarch's habitat. Also look for details about the butteflies'
behavior. These are important clues about how monarchs survive
the winter in Mexico.
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Report
Your Sightings: Seeing Winter Monarchs or Milkweed? |
All
monarchs do not go to Mexico. Please help us document where monarchs are
located this winter, and whether milkweed is available.
- Please
report
your sightings. >>
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Monarchs
(map/sightings)
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Milkweed
(map/sightings)
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Links:
Monarch Butterfly Resources to Explore |
- Monarch
Math: How many football fields would this year's monarchs cover?
>>
- Pie
Chart: Where Are the Butterflies This Winter? >>
- Pie
Chart: Which Sanctuaries Do Monarch Butterflies Select? Compare
Two Seasons >>
- Journal
Page: How Many Millions of Monarch Butterflies? >>
- Journal
Cover & Pages: Monarch Winter Habitat Journal >>
- History
of science: How 10 Million Became 50 Million >>
- Overview:
About Journey North's Monarch Butterfly Overwintering Study
>>
- Get
Ready to Track Spring Migration: How to Watch for Monarchs
>>
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The
Next Monarch Migration Update Will Be Posted on February 12, 2009.
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