Friday, June 19, 2026

Opening Day 2026

• Demonstration Monarch Tagging

• Rain or shine

• Free and Open to the Public

We tag Monarch butterflies (Danaus plexippus) as part of programs like Monarch Watch. A small, lightweight, coded tag is gently applied to the underside of a butterfly's hindwing. These tags do not harm the butterfly or affect its flight.

The primary purpose of tagging is to track the incredible multi-generational migration of eastern Monarchs from breeding grounds across North America (including Maine) to their overwintering sites in the mountains of central Mexico—a journey of up to 3,000 miles for individual butterflies.

By recording the tag codes when butterflies are captured and tagged here in Southwest Harbor, and then reporting any recaptures or sightings farther south along the route (or at overwintering sites), scientists can piece together valuable data. This includes:

• The origins of butterflies reaching the winter colonies

• Migration timing, pace, and routes

• Survival rates and mortality during the journey

• Geographic patterns and changes over time

This information helps researchers understand population dynamics, identify threats to the species (such as habitat loss), and inform conservation efforts to protect Monarchs.