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Video: Caterpillars head-butt intruders during turf battles

Fat, fuzzy caterpillars might not seem like the aggressive type. But new research reveals that some of the insects aren’t above using their heads to push and pummel other caterpillars out of their home territory. The study, published in the Journal of Insect Behavior, looked at four types of “leaf-tying” caterpillars, which fashion shelters from silk and feces between pairs of overlapping leaves. After allowing unsuspecting caterpillars to set up house in an artificial leaf tie, the researcher staged confrontations between the resident insects and would-be intruders. When a challenger approached, the headstrong rivals battled it out by pushing or even walloping one another with their heads, as seen in this video, until one retreated. In more than half of all interactions, the defender won. In 24% of the confrontations, the usurper emerged victorious, whereas in another 24%, the former fighters established an uneasy peace, sharing the same space they had been battling over. Defenders may be more successful at fending off aspiring shelter crashers because they have more to lose, having expended the energy to build the protective structures in the first place, the paper says. Although such humble poop and silk digs may not look like much to us, for these caterpillars, home is where the crap is—and they’ll spare no head-butt to defend it.