Humans Bred a New Monarch (By Trying to Save It)

What the film says

1. Captive rearing and release of monarchs is popular but controversial.

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2. Infected monarchs are less likely to complete migration, and migratory populations carry lower parasite loads than non-migratory ones.

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3. A 2019 PNAS study by University of Chicago researchers Ayşe Tenger-Trolander and Marcus Kronforst found commercially bred monarchs failed to orient south, were genetically highly divergent from wild monarchs, and had rounder forewings.

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4. The same study found that wild-caught monarchs reared indoors also failed to orient south.

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5. A 2020 Biology Letters study led by Andy Davis found captive-reared monarchs had 56% weaker grip strength than wild migrants, plus paler and less elongated wings.

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6. A 2021 Conservation Physiology study found 97% of radio-tracked captive-reared monarchs flew south to southeast, some detected up to 200 km away, even though only 26% oriented south in a flight simulator.

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7. Mexican overwintering colonies covered about 18 hectares in winter 1996–97.

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8. The western monarch count fell to 9,119 in 2024, one of the lowest on record.

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