If you were outside in front COAD this past Tuesday, you may have seen students behaving rather oddly, hanging out next to lampposts dueling with one another. These students are in Dr. Rosie Bolen’s Evolution class, and they were conducting a simulation of territorial contests. In the wild, males of many species fight with one another to obtain territories with valuable resources (e.g., food, water, shelter, or mates). Males who succeed in obtaining high quality territories will have more offspring. However, instead of engaging in physical fights over territories, males often exchange ritualistic display behaviors to signal their ability and/or willingness to escalate to physical combat (also called “resource holding potential”, or RHP). That way males who are not likely to win a physical fight (e.g., small, weak, or inexperienced males) can bow out before any injuries are inflicted.
Evolutionary theory suggests that there are constraints that keep these territorial contest signals honest. A weak male could bluff a high RHP (willingness to fight), which may gain him a territory he wouldn’t have otherwise obtained. But, if the other male calls his bluff and persists in the contest, the dishonest male is likely to suffer negative consequences (injury, lowered reproductive success, etc.). The idea is that individual males will produce more offspring if they signal their RHP honestly. The simulation the students performed tested this hypothesis that honest signaling can evolve by natural selection.
In the simulation, “territories” of low, medium, and high quality were set up by the lampposts in front of the Science Building. The students were randomly assigned different amounts of “energy units” and set out to obtain a territory. A student could challenge a territorial owner to a contest, at which point each student would spend one energy unit at a time, back and forth until one person gave up and left the territory. At the end of a trial, students who successfully obtained territories then had a number of “offspring” based on the quality of the territory they obtained and the number of energy units they had left. Students who didn’t obtain a territory produced no offspring.
The students conducted two different versions of the simulation. The first version simulated dishonest signaling, in which students were assigned energy units on a piece of paper they didn’t reveal to anyone else. Students could use nonverbal gestures to indicate their RHP and could bluff if they wanted to. In the second version, energy units were represented by pennies in a paper bag. Students shook their bags during the contests; the sound of the bag shaking could only be an honest signal of their RHP.
After conducting five trials of each version of the simulation, we analyzed the data and found that the results supported our hypothesis. On average, in the honest signaling trials the student had more energy remaining and produced more offspring than in the dishonest signaling trials. This experiment demonstrated that honest signaling can evolve by natural selection. This finding is supported by many field and laboratory studies of non-human animals, but the Evolution students discovered this result by experiencing it themselves in a fun and entertaining simulation of territorial contests.