Imagine that your neighbor sometimes goes into your house and takes some food out of your fridge. Sometimes you catch her, but you don’t get violent about it, you just push her out and tell her to not come back. But she keeps sneaking in.
Imagine that you’re also stealing food from your neighbors. Imagine that everybody in your neighborhood is stealing food from one another.
This is pretty much what happens with thieving ants (Ectatomma ruidum). These ants act like bouncers and kick out their neighbors when they catch thieves. They don’t get violent like you would expect from most ants. But they do put in effort to detect and boot out thieves.
Does this sound weird and not make that much sense? That’s what I think, and that’s why I’m working to figure it out.
In a paper from my lab that was just published in the journal Biotropica, we asked the questions: Does the vigilance against thieves respond to the intensity of thievery? In a world in which these ants didn’t steal from one another, thievery existed, would everybody be better off or worse off?
If thievery was some kind of mutualism or reciprocal altruism, then you’d expect the loss of thievery to harm productivity at the colony level. If thievery is truly exploitative and parasitic, then stopping thievery would boost productivity throughout the system.
So, we created that world-of-no-thievery, by removing all of the thieves, and measured productivity by collecting colonies at the end of the experiment. And we measured how the removal of thieves affected how sensitive colonies are to interlopers.
Here is the paper itself:
Jandt, Jennifer M., Elizabeth M. Hunt. 2015. Intraspecific Food-Robbing and Neighborhood Competition: Consequences for Anti-Robber Vigilance and Colony Productivity. Biotropica. DOI: 10.1111/btp.12234
So what did we find? Thievery is not a mutualism, and when you remove the thieves from the system, everybody is better off!
Colonies collect their own food, but they also are taking it from their neighbors. When the removal of food from the neighbors stops, then everybody gets more successful. In game theoretical terms, the cost of defecting and stealing — and being stolen from, is less worse than the sucker’s payoff of not stealing at all.
How this project happened in the context of an undergraduate institution:
My lab has been working on this system for a field seasons. (Here is the post about our first paper on the topic). This project was a collaboration among myself, Jenny Jandt, and Beth Hunt. Beth was a student from my university who conducted this project as a part of our International Research For Experiences for Students program. Her primary mentor for this project was Jenny, who had the experience and availability to mentor Beth throughout the field season.
You’ll notice in the methods that the project was conducted in the summer of 2011. After the field season ended, we worked on the paper on and off for a while, and somewhere in there, drove to Arizona to work with Jenny for a long weekend to work on this paper (and also another one.) Getting the paper out four years later is par for the course I’m playing on. But if you happen to be in Hawaii this week for the Tropical Biology meeting, you can catch the next installation!
This work was supported by the U.S. National Science Foundation (OISE-0854259 & OISE-1130156).