Why do Pheidole oxyops (Forel, 1908) ants place feathers around their nests?

1. The ant species Pheidole oxyops (Hymenoptera: Formicidae) has the particular behaviour of placing feathers along the edge of entrances to its nests. Here two hypotheses concerning this behaviour were tested: (i) P. oxyops, due to its essentially carnivore diet and particular nest structure (which acts as pitfall traps), uses feathers to enhance the capture of arthropods; and (ii) P. oxyops uses feathers as a strategy for obtaining water, as feathers could act as retainers of night moisture. 2. To test the first hypothesis, two plots with 20 pitfall traps were established, and inside each plot feathers were placed around half of these traps. It was expected that pitfall traps with feathers would collect a larger number of individuals and species of arthropods. To test the second hypothesis, all feathers were removed from 28 nests and water was supplied (wet cotton balls) to half of these nests. It was expected that colonies with access to an artificial water source would collect fewer feathers than control colonies. 3. Only the first hypothesis was supported. Our results indicate that feathers have the potential to enhance prey capture by P. oxyops providing the colonies with a more diverse and abundant diet. The ants' habit of placing feathers around the nest, which can be considered as a low-cost foraging strategy, could be particularly important during periods of low food resource availability.