Monarchs Are Using Their Sun Compasses

Monarch butterfly on swamp milkweed, Aug 2014 (photo by Steve Gosser)

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.

5 thoughts on “Monarchs Are Using Their Sun Compasses

  1. In 2018 I had the most delightful experience. I was in Cape May, NJ to watch the bird migration and the first day at the observation deck, the sky was littered with Monarchs. They were waiting there for the winds to change in order to cross the Chesapeake Bay and head to Georgia. Conservation people were catching and tagging as many as possible and enlisted me in the activity. Since then, I’ve been fascinated with Monarchs. This year I harvested 12 eggs and have released one butterfly so far. I have 5 in chrysalis stage and one J-ing since yesterday. I have 3 smaller cats to go. I also gave my grandsons a caterpillar and unbeknownst to us there were two eggs on the milkweed that I harvested for them. We have enjoyed watching them through all the stages of life thus far and spend way too much time sitting and staring at the cage! LOL!

  2. Last week I noticed a monarch flying due west down the street I live on. A couple blocks over I noticed a couple more flying west down that street too. They weren’t stopping. They like flying down the roads when they migrate.

  3. We have gathered eggs and raised the caterpillars to adult monarchs. We have tagged about 60 using tags from Monarch Watch and released them so that they can procede to Mexico.

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