Cooperative food transport in the Neotropical ant, Pheidole oxyops

Cooperation in foraging through information sharing is widespread in social insects and has been much studied. In contrast, cooperative transport of food items by groups of workers is less common and has received comparatively little attention. We investigated collective food retrieval in the Neotropical ant Pheidole oxyops, a ground-nesting species in which minor workers (mean body weight 0.6 mg) collectively transport larger dead insects back to the nest entrance. In total, 29% of items and 78% of total mass is transported collectively. We examined the configurations of ants carrying single experimental food items (weight 119 mg, size 10 x 10 x 1 mm) and found it to be non-random, with twice as many carrying ants at the corners as expected. This arrangement is achieved by preferential joining of corners and leaving of sides by carriers. Corner carrying increased carrying speed by up to 29%. Ants also preferentially carried food items from the front and back, versus the middle.