For decades biologists have focused almost exclusively on the presence or absence of certain indicator plant species in predicting salt marsh harvest mouse (Reithrodontomys raviventris) occupancy in the San Francisco Estuary. At the 2022 Annual Meeting we presented a new approach to assessing habitat for its potential to support the salt marsh harvest mouse which focused on function over form. This method guides the user to evaluate the habitat at a local and regional scale, and specifically addresses features important to individual survival, likely the single most important factor in population level persistence of this species which occurs in naturally isolated patches. During the 2022 Rangewide Survey for the Salt Marsh Harvest Mouse biologists utilized this habitat assessment tool to evaluate habitat and predict species presence before and after live trapping surveys at 55 sites. During this presentation we will present the results of the assessments, an evaluation of how accurately the assessments guided correct predictions, and recommendations for its use in the future. We will also address which habitat features from the assessment were most correlated with salt marsh harvest mouse occupancy (e.g., the value of marsh size versus vegetative cover). As salt marsh harvest mouse presence or absence has very important implications for many decisions made in the Estuary, the ability to accurately predict occupancy without costly and intensive live trapping is extremely valuable. Regional biologists should work together to continuously refine and improve these methods.