Richard S. Ostfeld
Institute of Ecosystem Studies

Collaborators: Felicia Keesing (IES and Bard College), Kenneth Schmidt (IES and Texas Tech University), Charles Canham (IES), Eric Schauber (IES and Southern Illinois University), Clive Jones (IES), and Brett Goodwin (IES and University of North Dakota).

"Mast production" or "masting" refers to the synchronous, episodic production of heavy seed crops by a population of plants. Heavy acorn production, which generally occurs once every 2-5 years in deciduous forests, is an example of masting. The evolutionary and physiological causes of masting have been intensively studied by ecologists, but the ecological consequences of this episodic pattern of resource superabundance are less well understood. Acorns are a highly nutritious food source for many species of mammals and birds, including white-footed mice. Mice store acorns for winter consumption, when food sources are generally scarce. We have used both long-term monitoring and experimental enhancement of acorn abundance to determine the effects of acorns on mouse populations. Long-term monitoring demonstrates that summertime abundance of mice is strongly correlated with acorn production during the prior fall. Experimental acorn additions indicate more mice survive the winter when acorns are abundant and winter reproduction only occurs when acorns are present. Following acorn mast years, as a result of higher over-winter survival and winter breeding, population growth starts earlier in the season, leading to higher peak densities of mice in summer.