On the morning of September 20th I got to see something I thought was absolutely hilarious. And I got it all on video. A male Bronze Jumper (Eris militaris) encroached on the territory of another male.
Go ahead, watch the video. As I’m filming, I’m trying to keep from laughing. The whole scene reminds me of a puppet fight. It’s nearly 3 minutes long, but I couldn’t stand to clip out any of it. The fight slowly escalates, and there is a winner. You may want to watch it in hi-res to see it better (click on the magnifying glass).
Doesn’t it remind you of a puppet fight? All puppets do is bat back and forth at each other. Notice how the spiders have their front two legs raised. This is the equivalent of a dog showing its teeth. It’s nearly a universal sign of aggression among spiders. I’ve come to think of it as meaning, “Leave me alone” or “Go away.” Did you follow closely enough to see which spider won?
I don’t know much about what’s going on in this video. Jumping spiders make retreats that they stay in when they aren’t out hunting. So I’m inclined to think that jumping spiders keep territories around their retreats. This one may simply have been guarding its retreat. Or perhaps there was a female among the leaves that I didn’t notice.