LAUSR

Abstract. Juvenile survival and growth are critical determinants of evolutionary fitness in most organisms. However, specific effects of population density and habitat quality on survival and growth of larvae vary widely among amphibian species. The Columbia spotted frog (Rana luteiventris), like many amphibians in the arid western United States, is a species of conservation concern, especially in the southern part of its range. To determine how density and habitat affect vital rates of Columbia spotted frog during the larval period, we performed a controlled experiment. Larval growth and survival in the Columbia spotted frog are determined by density of conspecifics and pond habitat. Density of conspecifics is the most important determinant of larval growth, and pond habitat type is the most important determinant of larval survival. Recommendations for repatriation efforts include starting populations with intermediate densities of larvae to optimize the size-versus-number trade-off.