Fairy circles or ghosts of termitaria? Pavement termites as alternative causes of circular patterns in vegetation of desert Australia

For southern African grasslands, many hypotheses have been posed and contested to explain bare circular areas (“fairy circles”) (1). Getzin et al. (2) “discovered” similar bare areas in arid grasslands of Australia and investigated their causes. Their data and modeling supported the hypothesis that soil crusting, water flow, and plant biomass feedbacks drove self-organizing vegetation patterns. Alternative causal factors, including termites, were investigated but rejected (2). Although we accept that water redistribution occurs between bare and vegetated areas in Australian desert grasslands, we have evidence that bare patches are subterranean termitaria, both active and inactive (abandoned).

We have frequently observed bare circular areas that appear as “gaps” as defined by Getzin et al. (2) but are actually pavement termitaria (3). These gaps are common across more than 1,200 km from Newman (Western Australia) to Newhaven (Northern Territory) (Fig. 1 A and B) in Triodia spp. (“spinifex”) hummock grasslands with scattered Acacia aneura (“mulga”) shrublands. Our preliminary excavations beneath circles at four locations (Table 1) revealed all gaps had termitaria typical of Drepanotermes harvester termites (3, 4). Termite chambers …

↵¹To whom correspondence should be addressed. Email: fiona.walsh2011{at}gmail.com.