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Monarch tags don't slow the butterflies

Just getting to your piece on monarchs Feb 12. To be sure, it is interesting to document the migratory habits of the butterfly. As a person who carries around a little excess weight, I'm interested to know the relative weights of the tag and the butterfly and whether the tag might reduce the migration distance relative to untagged butterflies. I guess the tag does not over-strengthen one wing over the other and make the butterfly fly in circles.

— Don Y., email submission

You're not the only one who has shown some interest in whether tagging programs for monarch butterflies are over-taxing the wings of these little creatures.

We posed this ponderable to David James, a Washington State University entomology professor who has been helped by an army of Southern Oregon butterfly enthusiasts catching, tagging and releasing monarchs to document where in California they migrate.

"I haven't weighed our tags, but rest assured they do not cause 'imbalance' of monarchs," James wrote in an email. "The fact that monarchs tagged in Ontario have been found alive in Mexico attests to that. Ditto our monarchs from Washington found in California. There is no evidence at all that tags affect monarch flight."

But James' email didn't have any numbers to quantify the relative weights, so we at Since You Asked put the hamster in the wheel, fired up the ancient hardware we call computers here and Googled your question.

We had to cyber-travel to New Zealand, where the monarch of New Zealand Trust did the weights. Turns out, the tag weighs the equivalent of 1.2 percent of the monarch's total body weight. Moreover, the tags are placed on a portion of the wing that generates lift, according to the trust. So there's a very slim chance that a tagged monarch may not fly as high as an untagged one, but it won't slow him down or shorten his journey.

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