The monarch butterfly (Danaus plexippus) is one of the most easily recognized native butterflies in the U.S. While the orange and black garden visitor used to be a common sight across Ohio from summer through early fall, visits are increasingly uncommon. Experts estimate that monarch populations have declined 90% in the last twenty years.
The monarch butterfly migration is one of nature’s most amazing feats. Millions of adult butterflies, each less than the weight of a postage stamp, make a 3,000-mile journey southward from their summering regions in the eastern U.S. to wintering habitat in Mexico. The overwintering adults return to the southern U.S. in March to mate and lay eggs for the first generation of adult butterflies. First generation adults continue to feed and mate as they journey north. Second and third generation adults mate and feed through summer, laying eggs for the fourth generation of migrating adults.
Threats to Monarchs
Monarchs face a number of serious threats to their survival.
- Overwintering habitat in Mexico has declined from about 27.5 acres in 2004 to a record low 2.5 acres in 2014.
- Erratic weather events can kill overwintering or migrating butterflies.
- The loss of native milkweed stands associated with habitat destruction and increased agricultural herbicide use means less food for larval (caterpillar) monarchs.
- Loss of late summer nectar sources means less food to fuel the adults, including fourth-generation adults on their migration journey.
- Insecticide use on host or nectar plants can harm or kill monarch caterpillars or adults.