Compairing Stalleicken & Reppert papers

Ed Reinertsen ereinertsen at iprimus.com
Tue Jun 21 23:06:33 EDT 2005


I thought some would like to see this, others have.......

I am not a scientist, just a guy comparing two papers.

I want to thank Chip, Don, Steve, Bill, Jacqui, and others for helping me. I
have learned a lot!

1) Do monarch butterflies use polarized skylight for migratory orientation?
Julia Stalleicken, Maya Mukhida, Thomas Labhart,
Rüdiger Wehner, Barrie Frost and Henrik Mouritsen

2) Polarized Light Helps Monarch Butterflies Navigate
Steven M. Reppert, Haisun Zhu, Richard H. White

The papers are not the "silver bullet" but just another step toward finding
out how the Monarch get to the overwintering sights during the fall
migration.

The Stalleicken (1) paper is one of the best papers I have read.
The large amount of resources, effort, energy, research, thought, etc. shows
in this paper. A very good job was done!
I can't say the same with the Reppert (2) paper

The Stalleicken paper used 331 Wild Monarchs, Reppert paper 11 Wild Monarchs

You would have to question the flight time for the Monarchs in Reppert's
paper.
Others using the simulator do not use data collected unless the butterfly
had been flying
for a 1/2 hour or better. The flight time for the monarchs in Repperts study
were much
shorter.

The Reppert's paper used 15 references, Stalleicken's used 34 references
Eight being the same in both papers
Note: four of Chip's papers were referenced

Quoting Stalleicken paper; "While we were in the process of writing this
paper, Reppert et. al. (2004) reported strong reactions of monarchs towards
an artificial polarizer covering-80 of the animals visual field of view.
These data contradict our finding using a 44- wide polarized light stimuli.
Therefore we decided to investigate."
snip........
"The experimental set-up described by Reppert et. al. (2004) did not mention
any sun shades. The sun even though not directly visible to the butterfly
inside the flight simulator caused an obvious light intensity pattern on the
simulator walls"

Stalleicken's conclusion;

" In conclusion, our study shows that monarchs can use their
time-compensated sun compass to orient in their normal south-southwesterly
migratory direction without relying on polarized light information. In other
words, polarized light input is not necessary for a time-compensated
celestial compass orientation in migratory monarch butterflies. Our data
further suggest that monarch butterflies are unable to make navigational
use, during their autumn migration of either a natural or an artificial
polarized light stimulus covering a large (up to 85 wide) zenith-centered
part of their visual field. Thus, it seems to be the sun and/or the
associated light intensity and spectral gradients rather than the pattern of
polarized light in the sky that plays the key role in the monarch's
time-compensated sun compass guiding the butterflies on their way to
Mexico."

Ed Reinertsen


 
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