Foraging ecology of an Australian salt-pan desert ant (genus Melophorus)

Abstract

Over the expanse of the salt lakes of the Lake Eyre basin lives a species of ant of the genus Melophorus (as yet unnamed), both on the edges of the salt-pan and on the salt-pan itself. Most of the foragers are small (~3.0–5.0 mm), but ~10% of the ants seen foraging are much larger (~7.0 mm) and may form a soldier caste. Foragers are thermophilic and show diurnal activity, displaying a single-peaked activity profile across the day, with activity time limited to 2–6 h at most each day (during the late-summer study period, 28 February to 28 March 2012). They forage largely for dead arthropods, but also occasionally bring home plant materials. Foraging success (not considering possible liquid food intake) is ~20%, resembling the success rate of their congener Melophorus bagoti, which inhabits cluttered environments. When displaced with food from a feeder, the ants head systematically and precisely in the feeder-to-nest direction, thus exhibiting path integration abilities involving celestial compass cues. The study of this species provides an interesting comparative perspective in contrasting desert ants of the same genus and thus genetic heritage inhabiting habitats differing in complexity of panoramic terrestrial cues as well as comparing ecologically similar species inhabiting the same type of habitat (in the present case, salt-pans) but differing in their phylogenetic relationships.