Why does the Rocky Mountain range act as a separating obstacle for the Eastern and Western Monarch populations?
Both species cross other mountain ranges on their way to their winter destinations. A: While they go over and through other mountain ranges, none are as high or as large as the Rockies. During the time that monarchs are migrating, it’s generally too cold in the Rocky Mountains to allow flight, so they serve as a fairly effective border. Q: What are the specific differences between the Eastern and Western populations? A: They can interbreed freely. There may be some differences in their susceptibility to diseases that are more prevalent in one population than the other.
