Monarch Watch Blog

Monarch Population Status

Friday, May 1st, 2020 at 10:01 am by Chip Taylor
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As of yesterday (30 April), the numbers are only 4 and 16 and that’s the way I like ’em. The 4 is the number of sightings of monarchs North of 40°N on the Journey North website. Four is enough, I don’t want to see more than that north of 40°N at this time of year. And the 16, that’s the number of monarchs sighted in Kansas so far this season—and more than half of those were reported in the last 10 days.

What does that mean and why am I happy about those numbers? It means that most of the returning monarchs that produce offspring that colonize the Midwest laid most of their eggs in Texas and Oklahoma, where it is warmer—conditions that allow them to develop faster than they would further north. Further, these numbers tell me there is a possibility that a large cohort of first-generation monarchs will move north of 40°N into the summer breeding grounds in May and early June. That should go well if the long-range forecasts are accurate, especially in the second half of May. The first half of June is forecast to be a bit cooler than normal, and if that comes true, recolonization of the northernmost latitudes could be reduced. All in all, this return recolonization appears to be normal and that’s encouraging.

As many of you may know, the West Coast monarch population has a steep climb to recover from the all-time low overwintering counts of the last two seasons (each less than 30,000). Getting back to the roughly 200,000 overwintering numbers that characterized most of the years prior to 2018 will take favorable conditions for several years. While it is impossible to tell how many monarchs survived the winter to reproduce in the last two months, the numbers of sightings in California reported to Journey North is encouraging. Further, the average temperatures and amounts of precipitation for California were in the near-normal range for March and April combined, and that’s a positive, since previous declines have been associated with extreme high temperatures and droughts for those months. Still, we need to keep our fingers crossed that the Western Monarchs will number more than 30,000 this coming winter.

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