INFLUENCE OF RESOURCE REMOVAL ON DEMOGRAPHY OF ATTWATERS POCKET GOPHER

Nutrient balancing is a foraging strategy whereby herbivores ingest a mixture of dietary items to ensure an adequate intake of nutrients to maintain individual health and reproduction. Recent findings indicate that terrestrial herbivorous rodents select dietary items from both di cotyledonous (dicots) and monocotyledonous (monocots) plants to obtain requisite nutrients, which may, in turn, influence demographic proces ses within the population. We investigated how availability of a major food source, dicots, affected population dynamics of Geomys attwateri , a fossorial herbivore. We removed dicots from the habitat in four pl ots and compared body mass, density, reproduction, recruitment, age-cl ass, sex ratio, length of residency, and spatial distribution of pocke t gophers in these areas to pocket gophers in areas with dicots. Remov al of dicots reduced the proportion of reproductive females and averag e length of time in residency within a plot for both sexes. These effe cts, in turn, resulted in reduced density of pocket gophers in areas h aving lowered dicot availability. Spatial arrangement of pocket gopher s within plots was not affected by removal of dicots but differed by s eason. Our experiment demonstrates the mechanism for reduction in dens ity of pocket gophers and shows a link between foraging strategy, inta ke of dietary items, and demographic processes.