Monarchs and temperature

Paul Cherubini cherubini at
Wed Oct 11 11:19:56 EDT 2000

Woody Woods wrote: 

> I think it's worth asking, though, whether a long-term warming
> trend is a greater threat down the road than the occasional 
> exceptional winters Brower has reported.

I agree its worth ASKING. But Professor Chip Taylor and other
monarch scientists cavalierly proclaim to public crowds and reporters
that global warming IS a threat without providing data or a model
that the public can evaluate for credibility.

Look what happened in 1989-90. At that time Lincoln Brower 
predicted in two magazine articles and in public lectures that 
the entire eastern monarch migration would collapse by the year
2000 due to deforestation in Mexico, pesticide use, urban sprawl,
etc. But he did not provide specific data or a model that outlined
the assumptions that would have to be made for these devastating 
impacts to be realized. Imagine how many people interpreted
Lincoln Brower's prediction as proof the planet earth was dying.
Imagine how much money in grants and donations for monarch
research and conservation his dire predictions generated. And 
look what actually happened in the 1990's - an increasing trend 
in monarch census counts at Cape May, New Jersey and a stable 
trend in monarch census counts in Mexico and a stable trend in
Ann Swengle's 23 years of 4th of July census counts.

With regard to your comments about "fragile energy budgets" 
"energetically delicate game" etc.,  there is abundant
evidence that lipid reserves are maintained at high temperatures.
During the 2 month, 2000 mile fall migration to central Mexico
David Gibo's and Peter Walford's research has found monarchs
maintain or gain lipid reserves despite migration through
regions with 90-100 degree F temperatures. During the winter
at the overwintering sites in Mexico, lipid reserves decline
yet the butterflies show little interest in nectaring to replenish
reserves despite abundant nectar sources at the overwintering sites.
Then in late winter,  nectaring increases as does the temperature and
lipid reserves, now low, stabilize or increase slightly. Then off the
monarchs go for another 2000 mile flight back north. The point is 
some of the butterflies are capable of this 2 month, 2000 mile 
return flight back north even though they leave the overwintering
sites in a lipid depleted state and fly through regions with 
warm spring temperatures.  

With regard to the ability of monarchs to adapt to climate
change, consider what happened when the North American
monarch was transported by man to Spain, Australia and New
Zealand 120-140 years ago. In a short time the seasonal
migration and overwintering phenomenon began in these 
foreign lands. It is also constructive to consider the wide range
of climates monarchs overwinter in from cold, cloudy and
rainy northern Calif. coast to warm, sunny and dry San Diego
to the extremely arid and nearly treeless Saline Valley near Death
Valley, Calif. in the Mojave Desert (2 inches of rain per year there,
5-20% daytime humidity and only the leafless winter twigs of 
elm trees to cling to at the Willow Creek site.)

Paul Cherubini, Placerville, Calif.

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