Experimental Support for Food Particle Size Resource Allocation in Heteromyid Rodents

Laboratory experiments were designed to determine if heteromyid rodents of different body sizes select seeds of an average size which is correlated with the body size of the granivore. Eight types of commercial seeds were used and 6 heteromyid species were tested. Although there was no correlation of average seed size selected and the body size of the individual granivore, there was a highly significant positive correlation (r = .95) of average seed size selected versus average body size of each group of rodents of a particular species. Thus small animals of a species select seeds of the same average size as large animals of that same species. There was a tendency for individuals of larger species to take a greater variety of seeds. We suggest that differential food particle size allocation can be a mechanism for reducing interspecific competition.