10 September 2020
Though 2020 has been an awful year it has a silver lining: Monarch butterflies are relatively plentiful. I saw my first monarch in late July. Now that they’re migrating to Mexico I see several every day.
How are they navigating to Mexico?
During their fall migration, Eastern North American monarch butterflies (Danaus plexippus) use a time-compensated sun compass to aid navigation to their overwintering grounds in central Mexico.— Antennal circadian clocks in migratory monarch butterflies
The compasses are in their antennae! Combined with a circadian clock that figures out where the sun ought be at any time of day, the compass compensates for the sun’s position and keeps the monarch heading in a southwesterly direction.
Monarchs can navigate better than some of us!
On Throw Back Thursday, read more in this vintage article: The Sun Compass.
(photo by Steve Gosser)
p.s. The article was written seven years ago when the monarch population hit a dangerous record low. The population rebounded in 2018-2019 but it’s hard to know if they’re safe yet. This population graph from Journey North was not updated in spring 2020. I’ll bet COVID-19 interfered.