crazymilkweedman wrote:Does anybody know or has is it even possible to know why the monarchs migrate to mexico? I mean the eastern monarchs bypass northern florida, southern alabama or louisiana where the temperatures in winter have to be on average warmer than way up at 10,000 feet in the mountains of mexico.
The majority of fall migrant monarchs MUST migrate up to the 10,500 foot level in order to have an excellent chance of surviving the winter. Northern florida, southern alabama and louisiana are all areas that experience lethally frigid temperatures (below 22-24 degrees F) very roughly every 5-7 years or so. The other problem with northern florida, southern alabama and louisiana is that they experience so many warm days during the late fall and winter that many of the butterflies would age too fast and break reproductive diapause before the native milkweeds are available (mid-late March).
Monarchs that emerge from their chrysalids too late in the season to have enough time to journey to central Mexico end up stopping in the coastal areas of northern florida, southern alabama and louisiana, etc. Some of them sometimes end up successfully passing the winter in those areas, some of them freeze to death and some end up laying eggs before the end of the winter.