Hungry and angry caterpillars headbutt to get their way

Do you ever get angry when you are hungry? Well, monarch caterpillars do too!

Older monarch caterpillars can strip a milkweed plant of its leaves in less than 2 weeks! Like teenaged humans, they need a lot of food to grow.

When caterpillars are hungry they head butt, lunge and knock other caterpillars out of their way to get to food. They use techniques that look like a combination of boxing and bumper cars to push other caterpillars out of their way.  The less food that is available to the caterpillars, the more likely they are to use force to try and get their way. It is like when their is only one piece of pizza left and you and your sister both want it!

Fact: Planting milkweed plants in your garden can help attract monarch butterflies. the butterflies will lay eggs that will  turn into caterpillars. Be careful though, most milkweed sold at garden centers has been sprayed with pesticides which will kill or stunt the caterpillars. Make sure to find organic milkweed plants!

Read the study and see pictures and a cool video of caterpillars fighting here: DOI: 10.1016/j.isci.2020.101791


Collie J, Granela O, Brown EB, Keene AC. Aggression is induced by resource limitation in the monarch caterpillar. iScience, 2020 DOI: 10.1016/j.isci.2020.101791