Butterflies and habitat corridors

[Mark Walker]

Laurel,

Your concern is valid enough, but the corridors are really intended for
providing a "migration" path between isolated pockets of habitat (primarily
related to localized species, which really don't migrate anyway).
Artificial corridors wouldn't be necessary if most of the habitat weren't
being destroyed, but alas, that is not the case.

Of course, when we're talking about providing corridors, we're usually
talking about cutting paths through heavily wooded forest - locations where
the butterflies being assisted would not normally be found.  It's true that
this opens up a whole 'nother can of worms, but I guess the bottom line is
that a few sections of forest are considered a fair enough price for saving
a species that shouldn't need saving in the first place.

The other thing to consider is that most butterflies (and mammals, for that
matter) will utilize corridors that help them minimize their required
locomotive energy dissipation.  I have no scientific reference for this -
it's just an observed phenomenon.  One could argue that it's only in such
corridors and open spaces that humans are able to observe, and therefore
take data.  But footprints and bounding butterflies are evidence enough -
one rarely finds butterflies that cross such corridors orthogonally.  It
seems that butterflies in particular will be "guided" by corridors, even
when there is no obvious benefit.  As a result, many butterflies are mowed
down at highway powerline crossings.

You are correct, there are definitely exceptions.  Many Nymphalids come to
mind, like the Polygonia species (Commas, etc.) and the Asterocampas
(Emperors and Emperesses).  But even in these woodland species, you'll find
that they prefer to use the forest openings to move from tree to tree.

Incidentally, many of the riparian species do like to "corridor", and in
fact the stream beds provide for very effective corridors for these species.
The Sara Orange Tip is a good example of this - they are almost always found
patrolling up or down canyons.  They are easily distracted anywhere they
cross a dirt road or railroad track.

Mark Walker.

Laurel Godley wrote:


What about butterflies that like a wooded (and moist) habitat?  I see more 
butterflies along stream beds... mostly wooded than I ever do in open 
fields.  I realise the article suggests that the butterflies studied (not 
all butterflies) perfer an open habitat but I would hate for anyone to take 
this article the wrong way and begin cutting down trees just to "create" 
corridors.

Laurel
from the sludge lagoons of San Jose, CA


>From: Danfosha at aol.com
>Reply-To: Danfosha at aol.com
>To: LEPS-L at lists.yale.edu
>Subject: Butterflies and habitat corridors
>Date: Tue, 15 Jun 1999 12:27:34 EDT
>
><http://ens.lycos.com/ens/jun99/1999L-06-10-09.html>
>
>BUTTERFLIES BENEFIT FROM WILDLIFE CORRIDORS
>
>Wildlife corridors linking distant areas can benefit species that rely on
>patches of fragmented habitat, two new studies show. The studies may help
>scientists and land managers design more effective corridors. Research at 
>the
>Department of Energy's Savannah River Site in South Carolina found that
>butterflies are more likely to move between habitat patches that are close
>together or linked by corridors than between widely scattered patches. The
>butterflies studied need open habitat and vegetation, and were unlikely to
>travel across wooded areas to reach distant open spaces. More open habitat
>butterflies were present in patches linked by corridors than in similar but
>isolated patches. "Corridors are often designed with the thought that they
>benefit all species living in a given habitat," says researcher Nick 
>Haddad.
>"Because habitat restricted species are most often threatened by
>fragmentation, corridors should be effective tools in conservation." The
>studies are in the current issue of the journal "Ecological Applications,"
>published by the Ecological Society of America.
>
>


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