Monarch Population Regions
Migratory monarchs in North America are divided between western and eastern populations. Then, within those two larger regions they are sub-dividisions based on regional dynamics.
US Western Regions
- CA-Overwinter: The series of groves along the California coast where monarchs congregate each winter
- Greater California: Where most spring and summer breeding occurs
- Southwest: this zone produces migrants both to Mexico and California and may have its own year-round breeders
- Northwest: Little is known about the dynamics and fate of monarchs of this region
Mexico Regions
- Mexico-Overwinter: The mountaintops where eastern monarchs congregate each winter
- Mexico-North: migratory monarchs pass through this area in the spring and fall, but little breeding is thought to occur
- Mexico-South: Monarchs in this zone are thought to be non-migratory (no monitoring)
US Eastern Regions
- South: The region where most spring migrants lay eggs and the first generation of the year moves north
- Southeast: some Mexican migrants make it as far as the Southeast, but this area also hosts a non-migratory population in Florida
- Midcentral and Mid-Atlantic: Spring and fall migrants pass through these zones but they are less important for breeding
- Northcentral: This is the zone that is thought to produce the majority of adults that make it to the overwintering grounds each fall
- Northeast: Although thought to be a less important contributor to next year’s population, still an important breeding area