Monarch Butterfly Navigation Solved
The monarch butterfly is able to navigate from the northern U.S. and Canada to Mexico without ever being there before.
The trip can take more than 2 months which is longer than the lifespan of some of the generations of butterflies.
The trip can be over 3000 miles and generations of the monarch butterflies are needed to make the because most generations only live for a few weeks.
So the butterflies need to mate along the way a produce a next generation of butterflies to continue the trip. The is all done without the butterflies ever being to their destination.
This has baffled scientists, but not they think they know how the butterflies do it. Scientists studied individual tethered butterflies recording from their antennas and eyes as they flew.
This revealed the monarch butterflies have an internal compass that give them the ability to navigate using the position of the sun.
Monarchs on the Decline
Millions of the butterflies migrate every year from the northern United States all the way to wintering grounds in the woodlands of Mexico.
The grueling trip can be around 3,000 miles and take 4 generations of monarchs to complete because their lifespans are short.
Fewer and fewer monarch butterflies make the trio because their populations have been declining throughout North America for around 15 years.
Current surveys at the wintering grounds of monarchs in Mexico showed colony size ever before recorded.
To approximate population size, scientists measured monarch numbers while they were assembled en mass at their wintering grounds.
During the 2013-2014 winter, the butterflies covered 0.67 hectares in Mexico’s forests, a drop of 44 percent from 2012.
Generally, the typical monarch butterfly coverage from 1994-2014 was 6.39 hectares– nearly ten times above the 2013 evaluation.
The loss of milkweed is the primary reason for the decline in the monarch numbers. The milkweed plant is the natural source of food for monarch caterpillars.
As the amount of milkweed across the United States declines, there is less food to feed the caterpillars which leads to their starvation and decrease in numbers.
The expanding use of genetically-modified GMO, herbicide-tolerant crops has caused a serious decline in milkweed and the natural feeding grounds for the monarchs.
