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)

Map of the different monarch population regions

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