Tracking Begins!
August 24, 2017 by Elizabeth Howard
  Sightings of southbound butterflies, intense nectaring, and the first overnight roosts are being reported. Share your observations and help tell the dramatic story of the monarch's journey to Mexico.  
Monarch Butterfly

Image by Anna-Lise Scheel of Halton Hills, Ontario

Fall Migration is Underway
Observers are reporting signs of a productive breeding season across the northern range. Get ready for an eventful fall migration!

Monarchs Are...
Monarchs are changing dramatically at this time of year, in physiology and in behavior. They are:

1. Becoming Migratory
Watch for signs of migratory monarchs:

  • flying in directional flight
  • clustering in overnight roosts
  • nectaring intensely

2. Responding to Daylength
Declining day length is a central cue that triggers the monarch's migratory state. In the northern breeding range photoperiod is falling by 20 minutes this week. This sends a signal that it's time to go to Mexico.

3. Emerging in Diapause
Beginning in mid-August in the north, adults are in diapause when they emerge from the chrysalis. They are full grown — but not reproductively mature. Their reproductive development is on pause. These monarchs will not complete development and begin to mate until next spring in Mexico.

4. Beginning a Long Life
The same hormone deficiency that leads to diapause also leads to increased longevity. Breeding monarchs live only 2-6 weeks; migratory monarchs live up to 8 months.

5. Accumulating Fat
Monarchs are shifting focus now from breeding to intense feeding. They must build body fat to fuel migration and to survive the winter in Mexico.

Watch for...
Migratory monarch butterfly flying in directional flight
Directional Flight
Harry Roberts
Monarch Butterflies Clustering in Roosts
Clustering in Roosts
Doug McEvers
Monarch Butterflies
Intense Nectaring
Joni House
Report Your Sightings
Report all monarchs you see — adults, eggs, larvae.
What to Report to Track Fall Migration Monarch Butterfly: Adult Sighted Monarch Butterfly: Egg or Larva Sighted
What to Report Adult Butterflies
map | list | animation
Eggs and Larvae
map | list
Monarch Butterfly Migration Map: Fall Roosts, Fall 2017 Monarch Butterfly Migration Map: Peak Migration Fall 2017 Monarch Butterfly Migration Journal
Fall Roosts
map | list | archives | animation
Peak Migration
map | list | animation



Next Update August 31, 2017