Hangry Caterpillars

When does the very HUNGRY caterpillar become very HANGRY?

This is Sandra Tsing Loh with the Loh Down on Science.

Eating is a serious – and DANGEROUS – business! I WILL “cut you” for that last piece of Valentine’s candy! Do our creepy-crawly friends feel the same?

Enter Joseph Collie and colleagues from Florida Atlantic University. They wondered if food shortages turn hungry caterpillars HANGRY.

In the wild, monarch caterpillars have been seen to “headbutt” others over food. To learn more about their fighting techniques, Collie’s team staged a cage match! They put groups of caterpillars in high, medium, and low food environments. 

THWACK! The amount of noggin knockin’ was highest when snacks were most scarce. What’s more, caterpillars were beat up only when they were on a leaf and just about to dig in. Attacks against caterpillars who were already eating were DOUBLE over those who were just foraging. Resting critters? Left in peace.

It’s a royal food fight out there! Hunger can trigger aggression – in all kinds of animals!

Even humans? Easter is coming. . . I need my Peeps! Don’t make me bite your head off. 


Collie, J., Granela, O., Brown, E. B., & Keene, A. C.. Aggression is induced by resource limitation in the monarch caterpillar. IScience, 101791 (2020). https://doi.org/10.1016/j.isci.2020.101791