Foraging and spatial ecology in a competitive environment: Polydomous carpenter ants (Camponotus leydigi) in a tropical savanna

Carpenter ants (genus Camponotus) are considered to be predominantly
omnivorous, mixing several feeding habits that include predation,
scavenging of animal matter, and plant-derived resources. Nitrogen
acquisition is crucial for the nutritional ecology of ant colonies since
growing larvae require sustainable protein provisioning. Here, we
investigate the foraging ecology and the spatial nesting structure of the
carpenter ant Camponotus leydigi in Brazilian cerrado savanna. By marking
workers from different nests with distinct colors, we revealed that C.
leydigi occupies physically separated but socially connected nests (up to
30 m apart), a phenomenon known as polydomy. Data on internest movements
in C. leydigi corroborate cooperative exchanges between nest units and
confirm several types of social connections, including internest transfer
of liquid and solid food, transport of colony members (brood, workers),
movement of solitary workers, and internest recruitment. Polydomous C.
leydigi allocate foragers throughout 1,700 m2, feeding mostly on termites
and plant-derived exudates. Influx of exudates is threefold higher
compared to solid food. Uric acid pellets excreted by lizards comprise 20%
of the solid diet in C. leydigi, a first quantitative assessment of this
peculiar type of nitrogen complementation in ants. We hypothesize that
nest decentralization in C. leydigi may reduce foraging constraints caused
by overt interference by its main competitor, the aggressive ant Ectatomma
brunneum that regularly blocks nest entrances. Our field study enhances
the importance of natural history data to clarify selective pressures
underlying the evolution of particular behavioral patterns (nutritional
and nesting habits) in social insects.