Monarch Population Status and the Weather

If you haven’t already read Chip Taylor’s early predictions for this year’s Monarch population, I reprint it below for your information. I found his explanation about how temperatures affect the survivability of the Monarchs pretty interesting.

Monarch Population Status – by Chip Taylor*

Based on first sightings, temperatures, probable egg distributions, generation length and early May conditions, my current prediction is that the overwintering population will be in the range of 4–5 hectares. At this writing, I see the population as trending toward 4 hectares. However, higher than average temperatures for May and June–August in the Upper Midwest could result in a population that is closer to 5 hectares.

The positive conditions in Stage 3 this year include the highest number of first sighting recorded in the central flyway since Journey North has been recording these data. That seems to tell us the relatively large population of 2018–2019 wintered well, in spite of reports the butterflies were abnormally active during the winter, and that they navigated from the colony sites back to Texas without experiencing high mortality.

Temperatures in Texas were lower than in 2018 which had the effect of again confining most of the egg laying by returning monarchs to Texas but also increased exposure to predators and parasites and increased generation length. Overall, the first generation produced in Texas and southern Oklahoma could be larger than in 2018 due to the larger number of returning monarchs. While that could be true, the predators and parasites could be more abundant this year. Unfortunately, we have no measures of the year to year variation in egg and larval mortality resulting from these causes.

Due to the lower temperatures, the average date of departure from Texas and Oklahoma for first generation monarchs should be a bit later this year. That may not be a bad thing since the forecasts indicate conditions for recolonizing the northern breeding areas won’t be favorable until the second half of May.

The bottom line is that we can expect monarchs to have another good year, not as good as 2018, but a good year – assuming near average temperatures of Stages 4 (May–early June) and 5 (summer).

*Taken from Monarch Watch Newsletter dated May 7, 2019.

Education

I know I’ve already written about the great news that the Monarch count for 2018-19 was up. Yepee! However, that doesn’t mean our work is over. We still need more habitat not only for Monarch butterflies, but also for all pollinators. Education is the key. Don’t hesitate to share what you know about pollinator conservation with friends, family, co-workers — even perfect strangers.

See Monarch Population Status for a more complete explanation.

See also Late Monarch Arrivals in Texas may mean Loss of Population Growth

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