Monarch butterflies raised in captivity rarely survive the species’ grueling, nearly 5000-kilometer migration. Now, researchers think they know why. When the insects were raised in indoor cages, they grew up paler (an indication of poor health) and 56% weaker (as measured in a grip strength test), researchers report today in Biology Letters. The reason may be that, although most butterflies survive when raised in captivity, only the strongest survive in the wild, The New York Times reports. The researchers don’t discourage hobbyists from raising monarchs, but they say it may not be the best way to restore dwindling populations around the globe.
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