The objective of this project are to examine the role of biotic interactions in a Chilean small mammal assemblage. Predation, plant-small mammal interactions, and interspecific competition are being studied with experimental exclusions of predators, and the most abundant small mammal herbivore, the degu rat, from fenced exclosures. Small mammal populations will be censused monthly, and predator diets and activity monitored by scat/pellet collections and analysis, and olfactory lines and call playbacks. Plant community changes are followed with point intercept sampling each 4 months, and monthly sampling during the annual growing season; soil samples every 4 months track seed densities. Similar initial conditions were present, and few changes in plant species cover, composition or seed densities have occurred since experiment initiation in May 1989. Numbers of degus in predator exclusion plots were higher during spring (September-November 1989): survival times and rates were significantly higher throughout the year. Responses of other small mammal species to predator/degu exclusions have been mixed. Continued support is requested for three years since changes in the small mammal assemblage and plant community are likely to be long-term. This large scale project represents the first long- term study of biotic interactions in a temperate Neotropical vertebrate assemblage.
