Monarch Watch Blog

Monarch Population Status

Friday, April 22nd, 2022 at 1:53 pm by Chip Taylor
Filed under Monarch Population Status | Comments Off on Monarch Population Status

I have looked at a lot of monarch and weather data over the years in attempts to understand the factors that influence the development of the population. These factors include the number of monarchs returning to Texas from Mexico, whether the migration is early or late, the mean temperatures in March, the timing of the emergence of milkweeds, the abundance of nectar sources and the temporal and spatial distribution of egg laying by returning females. Additional weather-related factors include soil moisture and rainfall.

That’s a lot to track and it gets confusing when trying to sort through the data over decades since the impact of some factors is affected by others. For example, droughts have a greater impact when temperatures are high than when they are low. While it will take months to sort out how the population develops this year, I’ve put together some distribution maps of monarchs and milkweeds based on photos submitted to iNaturalist to see how the conditions this year compare to those in 2021. As you will see, the numbers this year do not compare well with last year. The numbers of returning monarchs were lower this past March and the numbers of photos of milkweeds were also lower. Monarchs seem to be well ahead of emerging milkweed.

Overall, the population doesn’t appear to be off to a good start. However, the numbers could be somewhat misleading. Last year, we had a special project with iNaturalist based on an attempt to determine how severely the massive freeze in Texas in February 2021 affected monarchs and nectar sources. It’s possible that our appeal for help last year generated an unusual number of submissions. Still, as I write (6 April), the first monarch has been reported in southern Kansas well ahead of the milkweeds.

Here are links to the reports generated through the collaboration with iNaturalist last year:

Monarchs and the freeze in Texas

Nectar plants used by monarchs during March in Texas

Monarch – Danaus plexippus – 2022 N=392 (below left) and 2021 N=534 (below right)

Antelopehorn – Asclepias asperula – 2022 N=34 (below left) and 2021 N=207 (below right)

Green antelopehorn – Asclepias viridis – 2022 N=6 (below left) and 2021 N=45 (below right)

Zizotes – Asclepias oenotheroides – 2022 N=24 (below left) and 2021 N=68 (below right)

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