| Mark-recapture methods are commonly used to estimate abundance and density of wild animal populations. Advanced statistical models have been developed to analyze mark-recapture data, but for several reasons these models may not be appropriate for all long-term monitoring programs. For example, while in many cases wildlife monitoring programs are staffed by very experienced field personnel, agencies often do not have consistent access to people proficient in advanced modeling techniques. In this study, we investigated whether a simple population index, easily generated from mark-recapture field data, might be sufficient for determining long-term trends of deer mouse (Peromyscus maniculatus) populations on the California Channel Islands. Using mark-recapture data from five sites that span 18 years, we compared density estimates obtained from several commonly used mark-recapture models and further compared these estimates to index counts. Densities calculated by the models and the index showed similar patterns of population variation and trend over time for all five sites. For long-term population monitoring and communication purposes, our findings suggest that the use of a simple index may provide adequate understanding of population changes in island deer mice, and we present examples of how our results have contributed to a greater understanding of island ecology. |