[IMAGE 4 of 6] Winter rains had apparently washed away most of the external nest mound of this Pogonomyrmex salinus
colony, in central Washington state. In addition, large, jagged pebbles were either exposed by the erosion, or deposited around the nest entrance by the flowing water. In this series of images, dozens of workers
can be seen attempting to remove the relatively huge rocks, by grasping them with their mandibles
and dragging them away. Some of the objects appeared to be too large and heavy to be moved by a single ant, so in some instances, two or more workers would cooperatively carry them. It was also clear that the ants were completely unable to move some of the largest pebbles. Having a jumble of 'boulders' at the entrance to their nest would generally be unacceptable to these ants. The many nooks and crannies would make entering and exiting the nest very difficult (especially while carrying foraged seeds, etc), and spiders and other predators would be provided with many hiding places from which to prey upon colony members. In a situation like this, Pogos may sometimes choose to construct another nest entrance in a more suitable location.