They have lost vast portions of their habitats to farms and development, drought has killed the milkweed they feed on, and a severe and sudden storm in 2002 killed close to 80 percent of the overwintering monarch population in Mexico.
"That was a very extreme and unusual weather event. It's usually the dry season; there aren't big storms there, but they just had a lot of precipitation. That was followed by cold temperatures, so that juxtaposition of precipitation and cold just killed all the butterflies," said Karen Oberhauser, a professor in the Department of Fisheries, Wildlife and Conservation Biology at the University of Minnesota. "Clearly, that kind of storm is predicted to be more common under climate change scenarios."
The discovery of a cold trigger also raises the possibility of an unseasonal cold spell in the north disrupting the whole migration south.
A different pattern from fall
The temperature trigger is unexpected.
Monarchs take their cue to start migrating in the fall from decreasing hours of sunlight. While studying monarch diapause, a hormonal change that keeps adult butterflies from producing eggs and sperm, Oberhauser found that they showed the greatest response when exposed to changes in both day length and temperature.
"Migratory organisms need to respond to conditions in one place that will predict conditions somewhere else," she said. From an evolutionary perspective, it makes the most sense for them to respond to something that is constant from year to year, she said.
"So it is surprising to me that they are responding to temperature and not day length, which is obviously a fixed cue and is not going to vary from year to year," she said.
Reppert and Guerra tested a group of monarchs by keeping the day length constant from the time they were captured and only decreasing temperature. The butterflies still flew north.
"Subtle changes in day length might still have some influence, but it doesn't seem to be anywhere near as important as temperature," said Reppert. He plans to conduct additional research by using molecular and genetic tools to uncover what proteins and temperature sensory mechanisms are at work.
The monarchs themselves are a hardy lot. As Oberhauser's research shows, they can withstand temperatures up to 40 degrees Celsius and can even weather summer storms by latching onto a plant. What is at stake is their annual cross-country passage.
"It would just be a shame to lose this migration," Taylor said.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500
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5 Comments
Add Comment"How do Monarch's[sic] adapt when winter ends at different times each year?"
Reply | Report Abuse | Link to thisLike this:
"After 24 days, they released the butterflies into a flight simulator. Monarchs maintained under fall temperature conditions continued due south. Monarchs that were subjected to temperatures similar to those in their overwintering grounds in Mexico of between 4 and 11 degrees Celsius reoriented themselves to fly north."
You see, the climate is changing faster than animals can adapt. Usually, species would have many generations to adapt to natural variations in climate change. The unnatural variations we are causing with GHG emissions are WAY faster than what has happened in the recent geologic past.
BTW, the continued survival of monarch butterflies isn't "silly". Do you know how many other species along their migratory routes depend on them for pollination or food? What are the knock-on effects of a downward spiral in monarch numbers? Since you claim this is "silly", you should know these answers in order for you to make that assertion.
And the fact that we place no value on natural beauty is more a shortcoming of the current form of Capitalism we practice than anything you can help, so I won't hold it against you. What about natural "capital"? Shouldn't we account for that?
So, sault has a post in reply to Sisko. Where is Sisko?
Reply | Report Abuse | Link to thisTell me, is sault an endangered species that you have to protect?
Your article might have some merit, particularly in relation to habitat destruction. You are only talking about three hectares. Surely that can be reversed. Have any attempts been made to create artificial shade at near that site & to study the results?
I can not be bothered to comment further in light of you having deleted at least one post already. So, what is your policy in relation to deleting posts?
You invite people to comment. In my opinion, only obscene or highly abusive comments should be deleted. To delete comments otherwise is committing a fraud against those you have invited to participate.
If you feel so ill used, so mistreated, so harmed by the "fraud" you allege has been committed against you; feel free to leave.
Reply | Report Abuse | Link to thisYou comment on a site using a screen name to people you don't know beyond their screen name and whine that the creators of this site somehow owe you something.
I find it absolutely hilarious that you claim to have such a wonderful, perfect life; yet become furious that some comment you made was deleted?
Either get over it or leave. The creators of this site have the right to delete comments according to whatever standards they please.
I have no problem with them deleting comments as long as I know WHY they're deleting them. I have seen quite a few of my comments that I spent a lot of time researching and writing just get deleted while totally irrelevant / unscientific comments get to stay on the boards. I won't bother wasting my time making comments if I have no idea what sort of words will get them removed. SciAm has also started deleting ALL comments from some articles with no reason given either. If they're trying to foster better discussion, I can't think of many methods that could be worse.
Reply | Report Abuse | Link to thisIt seems to me that pretty much every site has guidelines so broad that they can pretty much delete whatever they feel like.
Reply | Report Abuse | Link to thisI honestly never put a huge effort into making comments anymore, partly because of that, and partly because (let's be honest) denialists never change their view regardless of the evidence.
As such, I think we all need to accept that if you don't like a sites decisions on this, then you should find another site.
Personally, when I bother to check comments, I enjoy seeing yours. But you need to do what you feel is best with your time.