Granivory in Arid Regions: Comparison of Australia with North and South America

Removal rates of seeds from experimental baits by ants, birds, and mammals were measured at four localities in the Australian arid zone, and the results compared with previously published data from North and South American deserts. Ants were the dominant granivores in Australia and birds are important granivores as well, although the experimental design underestimated consumption by birds. Mammals were insignificant consumers in Australia. Analysis of removal rates showed that North American mammals consumed a significantly greater mass of seed than all other groups. Removal rats of Australian and North American ants and birds were significantly less than North American mammals, but significantly greater than Australian mammals and South American ants, birds, and mammals. Thus, intensity of seed predation probably has the following ranking: North America > Australia > South America. The Australian data suggest that a relative scarcity of rodents has not resulted in intensified seed predation by ants and birds, and that convergence has not occurred in the intensity of seed predation in similar ecosystems on different continents.