Hiding in the tundra...[theory?]

[Guy_VdP at t-online.de]

This summer I was in Turkey in the Taurus Mts at approx 2000 m (some
6000 feet?) and later in the Swiss Alps (Valais) at about the same
altitude.
I noticed the same phenomenon, but did not think that far. I thought
they dived down and hid because they were usually flying low over the
(alpine) vegetation and rocks, where the wind is less noticeable and
the heat of the sun is not dispersed that quickly.
If you start hunting them, they will usually fly higher and thus cool
down more rapidly.
The difference was really noticeable on the slopes, where the same
species flew, but due to the more direct exposure to the sun's
radiation, were able to fly harder and especially longer (lost lots of
breath over there). Also on the slopes there was a warm wind coming out
of the valley, warm enough not to cool them down.
On the meadows though, the wind came from the north, from over the
mountain tops. Sometimes, when under my net, I could better use my
forceps to get them into my jar.

Guy.


MexicoDoug at aol.com schrieb:
> En un mensaje con fecha 08/05/2002 11:57:16 PM Central
> Daylight Time, 
> fnkwp at aurora.alaska.edu escribe:
> 
> Ken & Mark, et. al,
> 
> I remember once trying to photograph what I believed to
> be an _Icaricia 
> lupini_ (Lupine Blue) in a quite high mountain meadow in
> the Cascades of 
> Washington State (6,800 feet).  As I pursued, my victim
> gave me a cold 
> shoulder: it executed a number tricky manuevers including
> lethargic milk runs 
> to the next convenient plant, and falling to the ground
> and semidisappearing. 
>  True, Mark's observations at 12,000 feet were much
> higher, but it is also 
> true that as you get further north, air pressures are
> somewhat lower at the 
> same altitude.  By Alaska this certainly ought to be
> noticable. Perhaps the 
> latitude effectis not too significant but I hope some of
> the physicists on 
> the list can criticize the following attempt at a
> contributing explanation to 
> this adaptative behavior in such environments, brought to
> our attention by 
> Mark:  
> 
> "LIFT" and "FLIGHT" for butterflies.
> 
> - At 6,800 feet and 47 Degrees North latitude on a nice,
> warm summer day, 
> VERY unscientific sample of one (or a few), burrowing
> manuevers were 30/70 to 
> skipping-out flight manuevers.
> 
> - At  12,000 feet and 38.8 Degrees North Latitude on a
> nice soon to rain 
> summer day it appears that the burrowing manuevers are
> more common from 
> Mark's text, than the 30/70.  And on the Alaskan slopes
> they burrow through 
> rocks as seen by Ken:).
> 
> - Air pressure is about 55% that of sealevel at 12,000
> feet, let me guess 
> that this roughly will translate to 55% the lift for a
> spooked butterfly 
> using equivalent force as one at sea level with firm
> wings (e.g., 
> Papilionadae).
> 
> - Smaller butterflies, (like Lycaenidae) probably depend
> more on the "snap" 
> caused by near thorax wing deformation to initially
> generate the lift 
> necessary to ascend initially upon take off.  Thus their
> acceleration efforts 
> will be significantly less than the 55%, probably on the
> order of 30%. 
> (square of the 55%)
> 
> - Oxygen uptake for muscle function if aerobic
> respiration, at 12,000 feet 
> and 38.8 degrees N. may drop to about 80%, based on human
> aveolar oxygen 
> saturation, a poor, nonetheless worthwile reference
> point.  This could 
> attenuate the available flight energy an additional "20%"
> or more depending 
> upon their energy conversion efficiency for the
> butterflies.  And the 
> saturation may take longer to achieve at these pressures
> and "deficits".
> 
> - While alpine-tundra butterflies are undoubtable more
> evolved for their 
> environmental conditions, the basic premises above will
> have a strong impact 
> and the basic laws of physics not violated.  And I am not
> so sure that the 
> evolution would be so dramatic in many cases, because,
> the ranges of many of 
> these butterfly species include less austere conditions
> in many cases.  
> 
> - Of course, with a possibility of only 20% - 40% the
> energy-lift available, 
> I might decide to adapt, hiding by burrowing into the
> ground - if I were a 
> butterfy being pursued on "The Far Side".  And we think
> walking is 
> complicated, imagine how hard they have to work to fly!
> 
> Mark congrats on bringing your son with you, no doubt the
> experience through 
> his senses is nothing short of envious and will be
> remembered for a 
> lifetime...
> 
> Ken, you did study physics at one time, so please give me
> a hand here with 
> your opinion...
> 
> Best...Doug Dawn
> Monterrey, Mexico
> 
> 
> > Mark Walker commented, re Rocky Mtn. tundra
> collecting:
> > 
> > > Arctic Lepidoptera seem to be well equipped for
> falling at a whim and
> > > disappearing into the darkest depths of the arctic
> meadow landscape.
> > 
> >     They do indeed. Many times I have had a specimen
> under my net, and
> > have been unable to find it. The underside color
> patterns are amazingly
> > good camouflage, and the butterflies crawl way down
> into the vegetation
> > and appear to vanish.
> 
> 
> 
>

 
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