Monarch Watch Blog

Monarch numbers in Mexico: predictions and reality

Tuesday, May 24th, 2022 at 12:30 pm by Chip Taylor
Filed under Monarch Population Status | Comments Off on Monarch numbers in Mexico: predictions and reality

I was wrong, really, really wrong, and I’m happy about it. The numbers are in and they are much greater – 2.84 hectares – than I predicted. In my January 6 post “How many hectares in 2021-2022?“, I went to great lengths to explain why I expected the overwintering monarch numbers to be somewhere close to 0.80-1.2 hectares. I based my expectations on the anticipated impact of the drought in much of the Upper Midwest last summer, the extreme temperatures in July and August in that region, the later than average migration, the lower number of roosts reported to Journey North and the lack of emails declaring that large numbers of monarchs had been seen. None of those metrics hinted at a population larger than the 2.1 hectares recorded in 2020. Everything tended lower.

So, how did these metrics fail me or how did I fail to grasp their meaning? I’m not sure. I’ll try to reassess my approach. Alternatively, are there better metrics? The answer is yes. In the future, I will be using a different set of measures, ones that appear to be better at predicting how the population develops each year. Or, maybe I should follow John Pleasant’s lead and work out a way to count “eggs per stem” at a specific time each year. That’s what John does near Ames, Iowa and his predictions are often better than mine. This year, John wrote “My estimate was 2.1 with a margin that topped out at about 3”. Not bad – 2.84 vs “about 3”. Beats me!

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