[Leps-l] monarchs, reversal of orientation and overwintering temperatures

[Chip Taylor]

Doug: You have lots of points here and I don't have time to answer them all.

Here are some notes based on experiments that 
we've done and those by Reppert and his team.

Diapsue and the migration are not linked. They 
are two separate things. True, diapause precedes 
the migration in the fall but if you take 
migratory monarchs and break the diapause - they 
continue to show migratory behavior - for how 
long we don't know. Also, returning migrants are 
not in diapause by the time they reach TX.

As to the implications of the recent findings - 
yes, they could spell bad news BUT, there is 
still a lot we don't know about monarch behavior. 
To stay non-reproductive, monarchs exhibit a 
variety of behaviors to stay cool - that is to 
keep the JH from activating the reproductive 
system. They might well ramp up these behaviors 
by seeking the coolest and darkest parts of the 
forests if it gets progressively warmer at the ow 
sites. (A problem of course is that even the 
intact forests are becoming progressively 
degraded. On my last trip to MX, I was surprised 
to see how little understory remained at the main 
ow site.)

As to the temps - you need to consult the actual 
records from the ow sites as reported by Brower 
in several papers, The surrogate temps for the 
region are different, often being both lower and 
higher depending on the location of the recording 
station..

I'll send you a pdf of the most recent article - 
and if anyone else would like to see it - just 
send me an email.

Chip


>Chip,
>
>Thanks for the links, it is part of an 
>interesting study if you aren't squeamish about 
>amputating Monarch antennae and watching 
>carefully what happens!  If I can get a free 
>copy of this complete paper it will be 
>interesting to read ...  In the mean time, a 
>free pdf is available here:
>
>http://reppertlab.org/media/files/publications/natcomm2012.pdf
>
>which seems to cover the same experiment except 
>notably for the module of suspending some of the 
>Monarchs in Texas, in an artificial fall 
>condition during the migratory and overwintering 
>period to fool the Monarchs into thinking they 
>are still in Autumn ... effectively by swapping 
>the Northern and Southern equinoxes' to give the 
>Monarchs a form of Jet Lag that is undetectable 
>by some senses.
>
>The release point basically is at the same 
>temperature after the seasonal swap, correct? 
>The artificial autumn condition created seems to 
>be an average of around 61 degrees F, with 
>limits of something like 54 degrees F > temp > 
>68 F.
>
>This seems then to be contrasted with a current 
>estimate 36 degree F low (January) temperature 
>in the Mexico State & Michoacan State 
>overwintering region and another attempt to show 
>that prolonged cooling of undetermined length to 
>Monarchs already in diapause is a dependable way 
>to orient the Monarchs northward even in short 
>winters.
>
>The provocative conclusion seems to be if the 
>Monarchs can be given seasonal jet lag under the 
>right conditions and not notice while they were 
>in the lab --- that they gained a half season. 
>The suggestion that without experiencing the 
>cold temperatures in their Oyamel woods that the 
>Monarchs can be fooled.  It is interesting in 
>the sense that it argues that this effectively 
>says the Monarchs' "compass" is really only a 
>180 degree compass and I would infer is 
>requiring diapause and all the 
>biochemical/physiological reactions that 
>accompany it to calibrate with hemisphere of the 
>compass is "up".
>
>As an amateur and conservationist, think it is a 
>very constructive work, but a few more Monarchs 
>need to be seasonally jet-lagged (sans-antennae 
>amputees) to figure out the relationship between 
>entering diapause, flip/flopping navigational 
>'compasses', and if it all plays out according 
>to the hypothesis, precising for how long and at 
>what temperature (not studied between 36 and 61 
>degrees F) in a predictive sense these Monarchs 
>need to be exposed to go into diapause.  Unless 
>of course, the study is saying that diapause is 
>unrelated to the proposed N/S 
>calibration/inversion observed in these 
>laboratory Monarchs.  Right?
>
>That's what I get from this, where the 
>interesting diligence here, besides utilizing 
>this "disappearance bearing" (As a layman this 
>gives me discomfort since measurement of 
>disoriented butterflies after initial release is 
>being generalized, and not all individuals' 
>bearings are being counted  which has the 
>potential to introduce experimental bias - 
>though I have no idea how it could be done 
>better without GPS trackers or huge experiments 
>with tags via something like Monarch Watch) is a 
>laboratory attempt to control photo-period 
>length; and the implication to conservation of 
>the migration would seem to me not addressed 
>since even under the most pessimistic scenarios, 
>no one is saying that it will be 61 degrees at 
>those elevations in the Monarchs' dominion of 
>Oyamel woods.  But it does build on studies 
>during a time much less had been determined 
>about the 'compass', at that time which 
>suspected but did not confirm this at least as 
>far back as Herman, WS (1981)
>
>http://www.biolbull.org/content/160/1/89.full.pdf
>
>Best wishes
>Doug
>
>
>
>
>
>-----Original Message-----
>From: Chip Taylor <chip at ku.edu>
>To: Leps-l <Leps-l at mailman.yale.edu>
>Sent: Thu, Feb 21, 2013 1:45 pm
>Subject: [Leps-l] monarchs, reversal of 
>orientation and overwintering temperatures
>
>http://www.climatecentral.org/news/spring-chill-sends-monarchs-fluttering-north-15634
>
>http://www.cell.com/current-biology/abstract/S0960-9822(13)00087-0
>
>Coldness Triggers Northward Flight in Remigrant Monarch Butterflies
>
>Current Biology, 21 February 2013
>Copyright © 2013 Elsevier Ltd All rights reserved.
>10.1016/j.cub.2013.01.052
>
>Authors
>Patrick A. Guerra
>,
>Steven M. Reppert
>Summary
>Each fall, eastern North American monarch
>butterflies (Danaus plexippus) migrate from their
>northern range to their overwintering grounds in
>central Mexico [1,2,3]. Fall migrants are in
>reproductive diapause, and they use a
>time-compensated sun compass to navigate during
>the long journey south [4,5,6]. Eye-sensed
>directional cues from the daylight sky (e.g., the
>horizontal or azimuthal position of the sun) are
>integrated in the sun compass in the midbrain
>central complex region [7,8]. Sun compass output
>is time compensated by circadian clocks in the
>antennae so that fall migrants can maintain a
>fixed flight direction south [9,10]. In the
>spring, the same migrants remigrate northward to
>the southern United States to initiate the
>northern leg of the migration cycle. Here we show
>that spring remigrants also use an
>antenna-dependent time-compensated sun compass to
>direct their northward flight. Remarkably, fall
>migrants prematurely exposed to
>overwintering-like coldness reverse their flight
>orientation to the north. The temperature
>microenvironment at the overwintering site is
>essential for successful completion of the
>migration cycle, because without cold exposure,
>aged migrants continue to orient south. Our
>discovery that coldness triggers the northward
>flight direction in spring remigrants solves one
>of the long-standing mysteries of the monarch
>migration.
>
>_______________________________________________
>Leps-l mailing list
>Leps-l at mailman.yale.edu
>http://mailman.yale.edu/mailman/listinfo/leps-l