24 September 2007

Monarchs Trickle

The monarchs are beginning to trickle south on their migration to Mexico. So here one is on the very milkweed plant that seems to be butterfly manna. The spring monarchs ate it to the ground and now their distant relatives are back. Surprisingly, I watched this female lay eggs. I have always heard that the last generation born in Canada and around the Great Lakes flies all the way south to Mexico and overwinters there.

That's true, but it turns out that these fall migrants can jump start their reproductive organs if they get the hankering. This from Oberhauser and Solensky:
...many monarchs appear to become reproductive when they reach the southern US during their fall migration. The importance of this late reproduction to overall monarch population dynamics, and the environmental triggers that promote it, is still undetermined, but it suggests that an increase in the availability of milkweed in gardens and parks may trigger reproduction...
So, it seems like they are suggesting that as we humans plant more butterfly weed (and other milkweeds) in our gardens and/or if milkweed seems to be increasing in general, then we could be effecting the overall ecology of the monarchs. Maybe our gardens, in combination with longer growing seasons due to climate change, could help offset any decline in population numbers brought on by forest destruction in Mexico (but that doesn't mean we shouldn't stop that practice!).

If you totally want to geek out, here's another neat site: the Monarch Larva Monitoring Project. Or, Monarch Watch is full of info on the wonders of all things orange and red.

This cool site has an animated map of this year's migration.


toby said...

Between the milkweed and the Radiation Lantana I have more butterflies this year than ever. Probably the neatest site was going out into my front yard a couple days ago and seeing about 10 different types of butterflies all sipping away at the Lantana and Marigolds.

Lee said...

Wow! I'm working on a butterfly garden at a greenbelt in my neighborhood and will be planting 5 lantana plants for that reason alone. They are great, and they bloom beautifully off-and-on with almost zero maintenance.