DIETARY PREFERENCES OF 2 SYMPATRIC SUBTERRANEAN RODENT POPULATIONS INARGENTINA

We determined the dietary habits of two sympatric and allotopic popula tions of Ctenomys (C. australis and C. talarum) that inhabit a natural dune grassland on the sea coast at Necochea, Buenos Aires Province, A rgentina. Both species were found to be generalist herbivores as they consumed almost all plant species available in the grassland. Contrary to what we had expected, they fed principally on the aerial fraction of the vegetation, and preferred gasses over forbs. The greater propor tion of the subterranean fraction in autumn and winter in C. australis diets compared to C. talarum might be related to differences in the v egetation around the burrows they inhabit. Ctenomys australis and C. t alarum diets differed markedly only in September; however, these diffe rences may not have been totally seasonal, there may also have been a spatial effect due to the soil structure of the sympatric area. Ctenom ys australis and C. talarum distributions seem to be related to soil c haracteristics with individual animals feeding and selecting mainly am ong the vegetal species in their own home range. The results of this s tudy show that these species of Ctenomys present a feeding strategy wh ich is adaptative in subterranean rodents due to their high digging co st and to the low available energy to explore in their subterranean en vironment.