Subspecies and protection
Fred.Heath at power-one.com
Mon Oct 16 01:15:47 EDT 2000
I might be able to accept the hypothesis that some of the Monarchs
hung around the Saline Valley because the conditions were to their liking,
but your suggestion that the Bishop butterflies have a tougher time getting
to coastal southern California is certainly not true. These Monarchs
probably moved south along the eastern flank of the Sierras (which run
basically north and south) and then SW along the Tehachapi Mts until they
hit the Transverse Range (east-west tending mountains) and worked their way
through the passes (such as where I-5 goes). At that time of year, there is
abundant Rabbitbrush to nectar on along the entire route. Once they work
through the Transverse Mts. they are in the LA Basin and can easily move to
the coast. Interestingly, I found and reported one (after reading its letter
and numbers with binoculars) of these bright orange-tagged butterflies that
year in my backyard in Simi Valley (southeast Ventura Co.) within two weeks
of the release.
However Monarchs which find themselves in the Saline Valley are
really trapped and can't as Paul points out, go west or south or even east
for that matter. Although there are some passes to the south, the habitat is
less hospitable and if they managed to get through to the Panamint Valley,
they would end up at the south end in the middle of the Mojave Desert. Thus
it would be a lot less likely that a Monarch released from Saline Valley
could get to the coast even if it really had a strong instinct to do so.
On a related note, Paul mentioned that Mark Walker found a winter
roost in Anza-Borrego. Could Paul or Mark enlighten me as to exactly where
that was? Thanks.
> -----Original Message-----
> From: Paul Cherubini [SMTP:cherubini at mindspring.com]
> Sent: Saturday, October 14, 2000 11:35 AM
> To: leps-l at lists.yale.edu
> Subject: Re: Subspecies and protection
> The authors of that paper assumed the butterflies were
> "trapped" by the 10,000-11,000 foot mountains surrounding
> the Saline Valley. To test this hypothesis, I released about
> 300 tagged monarchs (caught at the roosts along the California
> coast) in the Saline Valley during the first week of November
> 1991 and a "control" group of 300 outside the valley at
> Bishop, CA.
> The Inyo mountains south and west of the Saline Valley are
> 10,000-11,000 feet tall, but the Sierra Nevada mountains
> south and west of Bishop are 13,000 - 14,000 feet tall.
> Thus, the butterflies released at Bishop had a more
> formidable barrier to cross to get back to the California coast.
> Within 10 days of release, some of the Bishop butterflies
> were recaptured along the California coast just north of
> Los Angeles and in the Santa Barbara area. Around half
> a dozen total were sighted back at the Calif. coast. So this
> group did not appear to have much difficult crossing
> the 13,000-14,000 foot Sierra Nevada Mountains. None
> apparently stayed in the Bishop area according to
> a local naturalist (Derham Giuliani) who was monitoring
> the situation.
> But no butterflies from the Saline Valley group were
> recaptured back at the California coast or anywhere outside
> the valley. When Derham checked the Saline
> Valley monarch roosts in late November, lots of the
> tagged monarchs were still there and they were still there
> in mid December.
> So it appears the reason the tagged monarchs released
> in the Saline Valley stayed there is because the butterflies
> detected proximate environmental cues that "overrode"
> the southward migratory urge. In other words, the mountains
> were no barrier to movement, the butterflies simply had
> no "desire" to leave the place (balmy winter climate,
> blooming Mule Fat bushes, and a permanent creek running
> through this desert area).
> > In other words, there does not appear to be any innate
> > requirement that they _complete_ the migration to the Pacific
> > coast. The migratory urge may be far less focused than many
> > people have assumed. This raises an interesting possibility:
> > that Monarchs from any part of the continent would, when
> > introduced into another part of North America, would migrate
> > along with the other individuals from that region.
> Exactly. In fact back in the late 70's when I was an undergrad
> at UC Davis, Prof. Art Shapiro urged me to get ahold of
> some tropical monarchs from a lepidopterist he knew in Samoa
> and raise them outdoors in late summer here in California to see
> if they would become diapausers in September and have a
> migratory urge to fly to the California coast. I never got around
> to doing that most important experiment. Of course in today's
> political climate an international transfer experiment could never
> be considered.
> Paul Cherubini, Placerville, Calif.
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