Thief workers and variation in nestmate recognition behavior in a ponerine ant, Ectatomma ruidum

Our findings give new insight into the relationship between nestmate recognition and cleptobiosis, intraspecific thievery of newly collected food items, in a neotropical ponerine ant, Ectatomma ruidum. The expression of discrimination of nestmates from non-nestmates varied among local aggregations of E. ruidum in a population at Barro Colorado Island, Panama. This result is due to differences in the behavior of the guard ants among aggregations, rather than differences in the expression of recognition cues by ants. Baiting experiments show that E. ruidum colonies in Panama have a greater tendency to have overlapping home ranges than a similar population in Costa Rica. The pattern of cleptobiosis, however, is strikingly similar between the Panamanian and Costa Rican populations.