Resource Patitioning in a Chilean Semi-Arid Small Mammal Community

Abstract

SUMMARY (1) Patterns of habitat and food utilization among small mammals were studied for 17 months in a Chilean semi-arid thorn scrub community. This community is dominated by spiny drought-deciduous and evergreen shrubs and low but variable winter rainfall. The four major small mammal species included three cricetid and one octodontid rodent, and three additional species (two rodents and one marsupial) which were low to sporadic in occurrence. (2) The four major small mammal species demonstrated significant patterns of habitat association including affinity for sites with high shrub cover and/or low to moderate grass and forb cover (three cricetid species), and affinity for sites with low grass and forb cover and high bare ground cover (the octodontid species). (3) Habitat overlap between these species as determined by similarity in utilization of trap and tracking stations over 3-month periods was high especially in comparison to values of overlap revealed in studies of California small mammal communities. (4) Trophic specializations among the seven small mammal species indicated three foraging guilds with two species each (herbivore, insectivore and granivore) and one omnivorous species were present in the community. Dietary overlap between the four major species was similar to that observed in more diverse California small mammal communities. (5) Niche overlap was relatively high for this community due primarily to high habitat overlap. Contrary to patterns revealed in California small mammal communities, but similar to other Chilean small mammal communities in the mediterranean zone, habitat overlap was usually greater than dietary overlap. (6) Levels of certain food resources including herbaceous plants, insects and seeds are at least equal and possibly greater in Chile than in California. This pattern in conjunction with the presence of similar dietary overlaps in both areas may indicate lower levels of competition among Chilean small mammals for those resources. (7) The patterns of resource utilization demonstrated by this community seem to be due more to ecological factors than to the evolutionary and biogeographical characteristics of the Chilean small mammal fauna.