Consumptive Driving, Part II

MexicoDoug at MexicoDoug at
Sun Jun 1 18:10:50 EDT 2003

Thanks for all the replies on the first "consumptive driving" post I 
made after three round trips by car and pick-up to Reynosa from 
Monterrey.  I am now back from a 4th trip, this time to Laredo, TX 
and back: all these Reynosa, Laredo trips in a 10 day period.

Grillotypes and transects aside for a moment, I would like to compare 
the Laredo (new) to the Reynosa (previously 'published' here) raw 
data results:

Laredo (Mostly North) and Reynosa (Mostly East) are both 150 miles 
from start and both have significant long desert highway conditions.  
There are still some nice stretches of Yucca trees in enchanted 
desert environments left where the humans haven't been too heavy 

LAREDO Road vs. REYNOSA Road MORTALITY: The butterfly mortality in 
quantity on the Laredo trip was of the same order vs. Reynosa.  I 
purposefully drove at 55 mph most of the way this time to Laredo, due 
to lessons learned.  At times I increased the speed to 70 - 75 mph to 
see if there were any differences.  Immediately, the kill rate went 
up to the previously seen 100 per trip - or higher.  Additionally, 
below 35 mph most all Leps escaped mortality.

There were about 25 Leps killed one way on my pickup in the late 
morning for Laredo.  Comparing with Reynosa, there were few if not no 
Queens (<10%), many more Lysides (66%), few swallowtails (10%), 
others about (up to 16%).  The reason for the lower number vs. 100 is 
principally due to my driving speed, as well as tailgating of trucks.

WHERE DO THE DEAD BUTTERFLIES GO: At one point I tailgated an 18-
wheeler for about 10 miles to 'research' a question given importance: 
Where do all the hit-and-run victim Leps go?  The results, while 
not "Boo!" surprising were very sobering.  

The ones impacting the grill or lower mostly vanished from my sight 
angle. However, many of the ones hitting the windshield were 
projected upwards, and then fell down quite fast, and slid quickly - 
as if hydroplaning (hoverplaning) - along the pavement fairly 
parallel to the road, and then slid-blew off to the side.  In few - 
say less than 10% - of the cases did they seem to get pancaked into 
to pavement by the next vehicles.

HOW CAN I FIND THE DEAD BUTTERFLIES: If, in 125 miles (about 200 Km) 
on any of the four roads between Monterrey and Reynosa and Monterrey 
and Laredo, these directionally correct calculations indicate 1 to 2 
million day-flying Leps are killed daily.  Taking the 1,000,000 
mortality rate as conservative, that each road has 2 - 4 shoulders 
and there are four roads, each shoulder has about 100,000 bead 
butterflies a day, or on average, one butterfly every two meters.  
Walking along the roadside eyes fixes in the grass, numbers of this 
magnitude are quite plausible.  It takes a keen eye.  I only stopped 
a few times.  Once I found none in 20 meters.  Another time, somewhat 
more than this 'average'.  And in two of the many high kill zones, 
several per meter.  The desert can be a windy place for butterfly 
wings, near major hauling lanes, especially.

relevant measures here.  (1) The statistics I have quoted as personal 
observations over several long trips.  I have been as unbiased as 
possible to comment on my observations.  (2) The statistical 
confidence in these numbers (are they statistically significant?).  
By collaborating the splats with the dead butterflies and getting 
ideas on how it varies with driving speed and vehicle type, and time 
of the day, independent measures give more statistical confidence in 
these results.  However, there is one additional set of observations 
I made.  At the end of the highway I slowed to about 45 - 50 mph, and 
watched arriving vehicles passing.  It is amazing how well splats can 
be seen on the windshields as they approach from behind, and much 
more amazing how as they pass one can look through the passenger 
windows through the windshields the travelers are behind and see the 
glinting squashed bug fluids they sport.  It was interesting to note 
that in the afternoon, arriving cars had 10 - 30 equivalent Lep 
splats, and SUVs ans Pickups, 20 - 50.  There were equal numbers that 
were very clean and completely pocked.  So I ignored the "Wash me" 
and obsessively clean cases.  The clincher is that a fast moving SUV 
was always at the high end of the range, and a slow moing one 
typically less splattered. While this is a nice measure for further 
study, first one needs to figure out how many splats are Leps and how 
many are non-Lep.  I eveballed the Lep numbers I am gioving based on 
my driving observations.  It was also interesting to note that the 
lower the grill, the higher the incidence of grasshoppers, bee, wasp 
and other insect impacts.

Additional new and troubling observations on this trip:

LEP-SAFE TAILGATING DISTANCE: There is a Lep safe following distance 
behind trucks where Lep mortality is a minimum with respect to the 
tailgater, if not avoided all together.  It is a dangerous less than 
2 truck lengths at highway speeds.  It would undoubtably lead to 
added human mortality due to excessive proximity.

varies greatly due to locality flora/fauna, even in a desert where an 
undiscerning eye is easily convinced all looks alike.  Certain 
localities had 10X to 50X the mortality of others.  It follows, that 
most of the mortality occurred in relatively smaller stretches of 

GARDENERS, TAKE NOTE:  Finally, the shocker, at least to me.  Lady 
Bird Johnson, Gardeners everywhere esp. butterfly gardeners, DOT's, 
please consider that highway beautification programs - greenways, 
etc.- may look beautiful, may be ecologically desirable under some 
conditions, but please "Remember the Girasol!":

REMEMBER THE GIRASOL!: Whether a conscious or unconscious effort, on 
the southbound lanes of the N. Laredo - Monterrey highway there is an 
aesthetically pleasing lining of one or commonly both sides of the 
road with Sunflowers (Girasoles).  I am talking about the three 
meters immediately on either side of the relatively narrow pavement - 
and no where else, for long stretches.  Having this pretentious, 
readily available oasis of nectar next to the incessant traffic 
stream is genocide to most of the area species.

Please think about it and "Remember the Girasol!".  The Girasoles 
resulted in at least triple the mortality.  Seeing 3 - 6 frolocking 
Lysides playing follow-the-leader into my windshield splattering 
repeated over and over on all the vehicles on the road was definitely 
disappointing, to say the least.  It didn't escape my thoughts that 
these were nectar sources and not habitat increasing host-plants.

Happy Butterflying...Doug Dawn
Monterrey, Mexico

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