Ecology of Pheidole oxyops Forel, 1908, a dominant ant in neotropical savannas

Abstract

Pheidole oxyops is a common and widely spread species in the central region of South America. Despite its ecological importance, relatively little is known about its habitat preferences, population dynamics and natural history. Here we provide information about the diet, daily foraging schedule, nest size and densities, and on the influence of habitat on the dynamics of P. oxyops colonies in southeastern Brazil. We found that P. oxyops is a habitat generalist, occurring in grasslands, savannas and forests. Although mean nest densities did not differ between the habitats we surveyed, the greatest densities were detected in the savanna plots, where up to 175 nests ha−1 were found. Pheidole oxyops presented an essentially predatory/scavenger habit, feeding on arthropod prey and especially on termites. Ant workers foraged during the day and the night at temperatures ranging from 14 to 28 °C. Nest mortality over a period of 1 year was positively related to initial nest densities, indicating a density-dependent regulation of the population. Nest growth rates were higher for small-sized—and thus presumably younger—nests than for large-sized nests. Overall, these life-history data reinforce the view that P. oxyops is a species typical of the Cerrado savannas, and a numerically and behaviourally dominant ant.