Foraging in the giant forest ant, Camponotus gigas (Smith) (Hymenoptera: Formicidae): evidence for temporal and spatial specialization in foraging activity

Abstract

The foraging behaviour of the giant ant Camponotus gigas, was studied in primary lowland rainforest in Brunei. Nests, found mainly in soil at the base of trees or in fallen timber, were present at a density of 14 per hectare. Foragers were active nearly 24 h per day but much higher levels of activity were recorded at night. By day major and minor workers foraged singly or in small groups on the ground, and by night they ascended in a steady stream into the canopy. It is suggested that the canopy is avoided during the day due to high temperatures and low humidity, and the ground is avoided at night due to increased predatation risks. Overall, < 10% of foragers returned laden suggesting that most feeding took place while foraging. The most common food item retrieved was fungus although arthropods and arthropod remains, vertebrate remains and small fruits and seeds were also gathered. Relatively more arthropods were retrieved at night. By watching individually marked ants, it was found that different individuals foraged by day and by night, i.e. the colony was divided into diurnal and nocturnal foraging subcastes, a form of polyethism which has never previously been reported in ants. There is no evidence that this is age-based, but as the subcastes are also separated spatially it is possible that temporal specialization is a consequence of site fidelity, given microenvironmental constraints on activity.

Keywords :

• ants
• Brunei
• Camponotus
• foraging
• Ortstreue
• polyethism
• rainforest