Size of the overwintering monarch populations - published data.

Chip Taylor chip at
Mon Oct 13 13:32:48 EDT 2003

>My take on the concern is that if %-mortality becomes very high, then in one
>of the down reproductive years, essentially the entire overwintering
>population could be wiped out, erasing the phenomenon (but not the species).

John: Your conclusion doesn't really differ from the one I offered in 
response to Stan. If the returnees are low in number, sooner or later 
the population will crash.

>Some quantitative measure of percent mortality over many years would be
>required to get at this basic question - is anyone working on that angle?

No. There has been no emphasis on the overall survival of the 
wintering populations. The winter clusters are not static and their 
density changes through the season and with the weather. This 
presents a conundrum as to how to measure the mortality of the 
wintering butterflies. It would take a well funded and well designed 
program to track this mortality for an entire season.  Surprisingly, 
it's been almost 15 years since any trained scientist has spent more 
than a few weeks studying the overwintering population. Most of the 
studies at the overwintering sites, and there are only a few, are 
conducted by Mexican students. Some of these projects are well 
supervised and will produce good results and others will not. Some of 
the funding for these projects comes from donations. There are no 
grants involved that I am aware of.

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