Many animals store food in times of plenty for use later when resources are scarce. Two general types of food hoarding occur: storing large amounts of food in a centralized location such as a burrow (larder-hoarding), and scattering many small caches of food throughout an individual's home range (scatter-hoarding). Kangaroo rats are desert rodents that use food hoarding as a strategy for dealing with the unpredictability of desert environments. Coexisting kangaroo rats differ in their food- hoarding patterns: some species are larder-hoarders, others are primarily scatter-hoarders. This study will use laboratory and field experiments to test three hypotheses about differences in food-hoarding patterns of kangaroo rats. Specifically, because larger kangaroo rats are aggressively dominant to smaller ones, smaller animals such as Merriam's and Ord's kangaroo rats should larder-hoard fewer seeds, make more widely-spaced scatter-hoards and move caches more often in response to theft than larger animals such as Panamint and desert kangaroo rats. Dr. Jenkins will also compare different populations of the same species from sites with different suites of competitors, to test the prediction that hoarding behavior is adapted to the competitive environment encountered by members of a particular population. This study is important for several reasons. First, desert rodents have been model systems for studies of the role of competition in ecosystem structure and function. Although the pervasive influence of competition among desert rodents has been well established, specific behavioral mechanisms that mediate competition have received little attention. As a key behavioral adaptation of kangaroo rats to desert environments, food hoarding is likely to be closely connected to competition among species. Second, optimal foraging has been one of the most fruitful areas of study in behavioral ecology in recent years because of the productive interplay between development of theory and empirical tests of predictions derived from theoretical models. As an aspect of foraging behavior, work on food hoarding has been mainly descriptive to date. This experimental study of food hoarding by kangaroo rats will contribute to a broader perspective on food hoarding by placing it in the context of optimal foraging ecology. Third, scatter-hoarding animals are important agents of dispersal for the seeds of many plant species. This study of factors that cause kangaroo rats to scatter-hoard vs. larder-hoard will lead to greater understanding of interactions between these animals and desert plant populations, with consequent benefits for conservation of desert environments.
