This award supports cooperative research on the systematic biology of fossorial (burrowing) rodents to be conducted by George Cox of San Diego State University and Luis Contreras of the University of La Serena in Chile. The work will consist of comparative studies of two aspects of fossorial rodent ecology: mound formation and population energetics and its impact on plant communities. The California group will focus on the first of these and the Chileans will emphasize the second. Nevertheless, basic data collection procedures will be used by both groups to obtain data essential to synthetic comparisons of the Californian and Chilean relationships. These two areas are highly similar in soil and climactic conditions. A combination of radiotracking and individual marking will be used to follow pocket gophers and coruros near their colony sites. Differences in mound building, food caching and tunneling will be studied to determine the effect of colonial behavior and differences in establishing permanent territories and nomadic behavior. Comparison of the behavior of these two groups of fossorial rodents will reveal characteristics that lead to the production of large-scale patchiness, consisting of mounds and temporary pond basins in North America but not in Chile. This will contribute to the understanding of recent evolutionary history of the two climate ecosystems. Both scientists and graduate students from both countries will participate in the field studies of site ecology. Thus the strengths of both groups will contribute to the science produced by this collaboration under the Science in Developing Countries program.