Captive-bred monarchs may orient themselves for migration, U of G study finds



PICTURE: A monarch is equipped with a radio sight tracker After

Credit: Alana Wilcox

Indoor-reared monarch butterflies always know how to fly south if they have enough time to orient themselves, according to a new study from the University of Guelph.

This finding is good news for the many nature lovers and school children who raise monarchs and then release them to help increase the number of people in trouble.

Monarchs are the only butterfly known to migrate long distances to warmer wintering grounds. While those born in spring and early summer only live two to six weeks, those who emerge in late summer feel environmental cues that tell them to fly thousands of miles south. , to central Mexico.

Recent American studies have suggested that captive-bred monarchs become disoriented when they emerge from their cocoons and cannot fly south. But this new research, led by University of California doctoral student Alana Wilcox and integrative biology professor Dr Ryan Norris, reveals that this may not be true.

Wilcox said previous research had only been carried out in a “flight simulator,” which involved placing the butterflies in an open vessel and then assessing which direction they were trying to fly. The U of G team used a flight simulator, but also followed a second group of monarchs that were released into the wild after being fitted with tiny radio transmitters.

These butterflies showed good southerly orientation, if they had enough time to orient themselves.

“We believe that the reason the monarchs released into the wild flew in the right direction is probably because they had time to calibrate their internal compasses after being released, which allowed them to fly in the direction from the south, ”Norris said.

The new study appears in the journal Conservation physiology. Integrative biology professor Dr. Amy Newman and Dr. Nigel Raine, professor in the School of Environmental Sciences at the University of California, contributed to the research.

The team stumbled upon the discovery almost by accident. They had investigated whether monarch caterpillars reared on milkweed grown in soil with a neonicotinoid pesticide would have difficulty migrating once they molted into butterflies.

They found that the pesticide did not appear to affect the migration of butterflies. But they noticed differences between the monarchs tested in the flight simulator and those that had been raised under the same conditions and released into the wild with radio transmitters.

Only 26 percent of the monarchs tested in the flight simulator (10 of 39 butterflies) showed weak southerly orientation after several minutes of testing; the rest flew all over the place. But almost all of the radio-tracked butterflies (28 of 29, or 97%) flew in a south-southeast direction from the release site and were detected at distances of up to 200 kilometers.

“Our results suggest that although captive breeding of monarchs may cause temporary disorientation for monarchs, once the butterflies have been exposed to sunlight and natural signals from skylights, they can establish appropriate orientation by using their sense of the right direction of flight, ”said Wilcox.

This post-release orientation process can take anywhere from 24 to 48 hours, Norris added.

The findings are good news for the thousands of butterfly enthusiasts and educators who fear that breeding endangered monarchs in captivity could hamper their instincts to fly to their wintering grounds in Mexico.

The team notes that the results only apply to late-summer monarchs, who perceive environmental cues like shorter days as signs it’s time to migrate to Mexico.

“Although the environmental conditions of our experience may differ for monarchs reared by amateurs, our results suggest that captive breeding remains a valuable educational tool for highlighting the natural history and biology of butterflies,” said Norris.

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Contact:

Dr Ryan Norris

[email protected]

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