Comparative prey transport behaviour, demographics, and diet of two sympatric driver ant species in a central African rainforest

Sebastian Huber, Luke L Powell, Maximillian P. T. G. Tercel 

Driver ants (Dorylus) are considered to be the predominant invertebrate predators in Afrotropical ecosystems, conducting vast predatory raids across the forest floor. Although these raids are fundamental to driver ant ecology, quantitative data on the diet and prey transport behaviour across the worker demographic spectrum remain limited. We describe prey transport biomechanics and diet composition of Dorylus wilverthi and D. sjostedti from primary and secondary rainforest in mainland Equatorial Guinea, using 2,933 prey samples from 25 raids across 16 colonies (4,610 measured workers). Both species exhibit continuous worker polymorphism but differ in demographic structure. Contrary to earlier studies, D. wilverthi shows three distinct worker size modes, including a large worker mode absent from D. sjostedti (two modes). Worker allometries and size range did not differ between species. Prey mass increased with worker mass (β = 1.37), whereas relative load per worker declined with worker mass (β = −0.63), indicating a size-dependent division of labour consistent with classical strength-scaling laws. Ants engaged in cooperative transport carried heavier absolute loads than solitary carriers even when accommodating that loads are shared. Cooperative transport was therefore primarily associated with larger prey items and did not function mainly to reduce individual loading, instead extending the upper limit of transportable prey. Driver ant diet was highly generalist with 25 prey orders identified; D. wilverthi and D. sjostedti exhibited near-complete order-level diet overlap (Pianka = 0.956). Our multifaceted approach provides a detailed description of prey transport ecology in driver ants, connecting worker morphology to prey characteristics, and reveals the shared biomechanical constraints of two ecologically similar driver ant species.