—Jeni Casinelli, Education & Program Coordinator
Has spring yet arrived? The weather seems to be getting warmer, the snow is melting, and daylight is becoming more plentiful. But are these sure signs of spring's arrival? Well, temperature and weather seem to be somewhat variable these days, warm one day and cold the next, so it can be hard to say on just weather alone. There are, however, a few sure signs that spring is on the horizon. What are they you ask? One of them is the return of the monarch butterflies.
Typically every March, monarchs who have been roosting in the mountains of Mexico and California head north after a long winter. Those who have overwintered in Mexico will head east of the Rocky Mountains while those who have overwintered in California will head west of the Rocky Mountains.
This generation of monarchs returning north is quite peculiar and different from those monarchs that we see from May to August. These butterflies have been alive since last September and October, surviving on stored fat in Mexico and California. However, before heading north, overwintering monarchs will find a mate at their roosting spot. Upon northern arrival, they will lay eggs and a new life cycle of monarchs begins. This life cycle will occur 3 more times, before the fourth generation of the year will head south for the winter. This last generation will live 6 to 8 months versus the generations who don't migrate and only survive 3 to 5 weeks.
So then you might ask, if for the winter months monarchs can survive in the warm south, then why do they need to migrate at all? The answer is quite simple. Monarchs cannot survive the cold winters of the north, but their southern roosting areas do not contain milkweed, food necessary for the larva stage. Thus, they migrate between the two.
I always find it fascinating that such a small critter can have such a complex life cycle which is necessary for the survival of the entire population. So now, if you have spotted the returning monarchs this year, it is a sure sign that spring has arrived and the snow season is at its end. I suspect they will be arriving shortly. Keep your fingers crossed!