IERC began working with mountain and foothill yellow-legged frogs in 2005, assisting on a project tracking both species using VHF transmitter belts in a northern Sierra Nevada stream. IERC assisted in the capture, safe handling, and weekly monitoring of frogs for this project lead by consulting company, MGW Biological. After transmitters were removed in 2007, IERC continues to monitor this frog population by visiting the site twice a year to survey for marked frogs and mark new frogs. Our goal is to estimate survival and population size of these two species of frogs within this system. This project will help us understand more about the relationship between the species where they co-occur and their population persistence at the limits of their ranges.