This just in from Journey North:
Monarchs are scarce this summer across their breeding range because of two key factors:
1. Record Low Last Winter
There were only 60 million monarchs wintering in Mexico last winter, 80% below the 350 million monarch average. The area of forest covered with monarchs was only 3 acres, compared to the 17-acre average. Why so few? Drought and excessive heat during summer 2012 resulted in low reproduction last year.
2. Cold Spring, Slow Migration
This spring’s unusually cold temperatures across the middle section of the country delayed the migration northward. The season’s first monarch generation was slow to develop in the southern U.S. and late to migrate northward.
What’s Happening Now?
Low numbers, cold temperatures, and slow spring migration meant few monarchs across the north in June. Monarchs must have a productive breeding season this summer for the population to recover.
During the breeding season, monarchs can produce a new generation in about 30 days, resulting in four generations. The monarchs that migrate to Mexico this fall will be the great-great-grandchildren of those who left Mexico last spring.
A Missing Generation?
By arriving late this spring across their breeding range, monarchs may not have time to complete four generations. This could result in a small fall migration and low numbers in Mexico again next winter. However, monarchs have a high reproductive potential and they breed across a large region. Breeding success in one area can counteract the effects of poor conditions in another.