[Leps-l] [leps-talk] Monarch Armageddon

[drivingiron at comcast.net]

Folks,

We are going to cause the extinction of the Monarch by beating it to death. 
Can't we talk about sand gnats or girls or something else for a while?

Jim Taylor

-----Original Message----- 
From: Paul Cherubini
Sent: Friday, February 15, 2013 1:40 PM
To: Leps List
Subject: Re: [Leps-l] [leps-talk] Monarch Armageddon

On Feb 15, 2013, at 8:44 AM, Foley, Patrick wrote:

> Monarchs are unlikely to pay attention to latitude lines.

The opposite is true.  The onset of reproductive diapause,
clustering behavior and migration in the late summer and fall
is well known to vary depending on latitude; e.g. diapause
starts the first week in August near the Canadian border
(west of Ontario)
http://i85.photobucket.com/albums/k75/4af/gryglc.jpg
and starts in early September down at the latitude of
Oklahoma and Arizona.

> You probably recognize that the future climate zones
> will not be the same as they are today. That is one
> reason for the uncertainty I refer to. US Development
> and Mexican land use change also create uncertainty.

There has always been climate change and land use
change.  These land use changes (e.g. sprawl,
intensification of agricultural and roadside management
practices) will reduce milkweed abundance in the future,
but not hardly eliminate the plants.  Therefore there will be
fewer migrant monarchs in the future, but still
millions of them just as there will still be millions
of milkweed plants.

> The migratory distances of Monarchs in California are
> very different than those in Eastern North America.

The opposite is true. We already know from tagging
western monarchs that 1000's of them migrate to
the overwintering sites in central Mexico and therefore
migrate virtually the same distance as eastern Monarchs:
http://swmonarchs.org/az-recoveries.php

> If people are worried about the collapse of the
> Eastern migration down to a diversity of short
> migrations, why wouldn't the western migrations
> support that worry?

As I just pointed out, some western monarchs migrate
as far as eastern monarchs do. And we've known
since 1991 that if a California coast monarch is
mailed to eastern Montana or North Dakota for release
in September it will migrate to the overwintering sites in
central Mexico. So there is no such thing as a "short
distance" migrating monarch to begin with. Both
the eastern and western monarchs have a 2-3 month
long window of time  August - early Nov) when
the migratory instinct is turned on.

> there are plenty of dark hollows in the
> Appalachians that could conceivably offer
> overwintering sites.

Nope, there are no places nowadays in the Appalachians
that are reliably free of sub or near zero degree F overnight
winter temperatures, which, of course, would be lethal to
overwintering monarchs. And no places in that mountain
range that will be reliably free of sub or near zero
temperatures 100 years from now. So it is not plausible
to imagine that a short distance monarch migration evolve
in the eastern USA within the next 100 years.

> Your claims about the Mexican overwintering sites
> go against published literature. Could you provide
> some published scientific literature to support your claim?

I wrote: "no photographs exist substantiating this alledged
"serious loss of Mexican overwintering habitat."
What the photos actually show is something like this:
http://i5.photobucket.com/albums/y189/mastertech/9005.jpg
In other words, the photos show virtually no change in forest
cover during the past several decades on the south and west
facing slopes of the mountains where the monarchs overwinter.
There have been a couple minor exceptions like some forest
fire damage on two mountains with small colonies during the
drought of 1998 and the butterflies adapted by merely
shifting the location of their clusters to an adjacent unburned
portion of forest.  And there was one heavy forest thinning
incident at a medium sized colony (Lomas de Aparicio)
http://earthobservatory.nasa.gov/IOTD/view.php?id=8506
but those fir trees will grow back to their former stature
in only 40 years.

So overall the photographic record shows only a minor,
temporary loss of Mexican overwintering habitat and that
loss didn't have consequences because the butterflies merely
relocated to nearby vast expanse of intact forest.

> Some people very reasonably worry that the great
> long-distance Eastern migration might dwindle away
> if, as you recognize happens elsewhere, the Monarchs
> find some shorter migration gives them higher fitness.
> Why is this point so hard for you to grasp?

At temperate zone latitudes there's no such thing
as a "shorter migrating" monarch to begin with, just as
there is no such thing as a "non-migratory" monarch
at temperate zone latitudes. We learned from tagging
back in 1964 that if an Ontario monarch (an eastern
monarch) is shipped to Reno, Nevada in September
it will migrate a very short distance to the California
coast overwintering sites.  And we learned in the 1970's - 1990's
that if California coast monarchs are shipped to eastern
Montana, North Dakota, Colorado or New Mexico for release
in September many will journey the very long distance
to the overwintering sites in central Mexico.

Paul Cherubini
El Dorado, Calif.
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