[Leps-l] monarchs, reversal of orientation and overwintering temperatures

[Chuck Vaughn]

What bothers me about press releases like this is the lack of historical perspective and the apparent lack of curiosity about the past.

I don't know the answers to these questions but I think about them anyway.

How long has the monarch migration been going on?

Does it extend back to the last ice age and beyond?

How was it impacted by earlier warm periods like the Medieval Warm Period, the Roman Warm Period and earlier warm periods, all of which have been shown to be as warm or warmer than today?

I assume monarchs were around during the last ice age. What was their behavior then? Did the migration shift south?

Assuming the speculation part of this study is correct, did the migration stop during past periods of higher temperatures? If they did stop then they must have resumed during cooler periods. Why would it be assumed that if they stopped in a warmer world today that they could never resume in a future cooler period?

Is it possible that the migration just shifts north during warmer periods?

Why do the authors of a paper that must have had required a lot work feel it necessary to add what appears to many of us as speculation in a press release? Are the direct results of the work not interesting enough?

Maybe the subject of research for their next paper should be to determine at what temperature the migration stops. Or did they do this here?

Until someone can explain to me how the migration persisted through warmer and cooler periods in the past but can now no longer do so, I can't help but be skeptical of the fragility of the migration.

If my idea that the migration shifts north or south with temperature could be proven correct then that would be a strong argument for a robust migration.

Chuck



> Doug and Chip:
> 
> I havn't read the original paper yet, but from reading the 
> abstract, fall migrant monarchs exposed to 24 days of chilly 
> temperatures flew north when tethered in a flight simulator:
> http://reppertlab.org/tools/flight-simulator/ 
> 
> So the study does not actually demonstrate the direction(s)
> the cold treated butterflies would fly if they were released 
> into the wild. So I do not see how the authors can legitimately 
> make this claim: "Our discovery that coldness triggers the 
> northward flight direction in spring remigrants solves one of the 
> long-standing mysteries of the monarch migration."
> 
> Now on the basis of that crude experiment, look at what
> the science news articles and the lead author of the study 
> are telling the public:
> 
> http://www.sciencedaily.com/releases/2013/02/130221141259.htm
> Coldness Triggers Northward Flight in Monarch Butterflies: 
> Migration Cycle May Be Vulnerable to Global Climate Change
> 
> "The temperature of the microenvironment at the overwintering
> sites is a critical component for the completion of the migration 
> cycle," said Steven M. Reppert, MD, professor of neurobiology 
> and senior author of the study. "Without this thermal 
> stimulus, the annual migration cycle would be broken, 
> and we could have lost one of the most intriguing 
> biological phenomena in the world."
> 
> and
> 
> "The more we learn, the clearer it becomes that the 
> monarch migration is a uniquely fragile biological 
> process," said Reppert. "Understanding how it 
> works means we'll be better able to protect this 
> iconic system from external threats such as global 
> warming."
> 
> Googling "monarch butterfly cold" will bring up
> many more articles about this study.  
> 
> Paul Cherubini
> El Dorado, Calif.
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