VERY hungry monarch butterfly caterpillars get hangry, resulting in them headbutting and lunging at each other in an attempt to secure food. "The less food that is present, the higher their level of aggression," says Elizabeth Brown at Florida Atlantic University. Monarch caterpillars (pictured) are found across North and Central America. They only eat milkweed leaves. Brown and her team gave the caterpillars three different amounts of food and found they attacked each other significantly more when the leaves were scarce.
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