Type: report

Article abstract: In 2005, we implemented a new monitoring program for the endangered Stephens’ kangaroo rat (Dipodomys stephensi, SKR) on Marine Corps Base Camp Pendleton (MCBCP). It is a relatively simple, multi-tiered, habitat-based, adaptive monitoring program designed to track yearly trends in the total area occupied by SKR on base. There is a two-phased approach for sampling. The first phase involves a complete search for any potential kangaroo rat sign and measurement of habitat and environmental variables. If any potential sign is observed, two to four days of live-trapping are conducted for the second phase. Live-trapping is necessary to determine if plots are occupied by the Stephens’ kangaroo rat and/or the Dulzura kangaroo rat (D. simulans, DKR). In order to provide continuity with previous monitoring efforts, we also live-trapped 10 SKR grids that were historically monitored biennially from 1996 to 2002. After five years of the current program, we present a multi-faceted report on SKR monitoring with: 1) Multiyear trend analysis for the past five years (2005 to fall/winter 2009/2010). This includes assessment of factors associated with SKR occupancy, probability of detection, colonization and extinction; and 2) A monitoring program evaluation, optimization, and recommendations for future monitoring. This includes re-evaluation of the sampling area and power analyses of current and proposed alternate sampling scenarios to detect changes in the occupancy of SKR on Base. Multi-year Trend Analysis: Overall, the estimated area occupied by SKR in 2009-10 on MCB Camp Pendleton has been relatively stable since 2007-8 (within a single standard error) and is greater than the initial years of monitoring at MCBCP in 2005-6 and 2006-7. Within the high suitability stratum (which defines almost all know SKR habitat), we estimated SKR occupied 118.4 ha (SE=39.1) in 2009-10, in comparison to a high estimate of 147.3 ha (SE=39.1) in 2008 and low estimate of 60.0 ha (SE=24.2) in 2005. We detected no SKR in the medium suitability stratum. In areas occupied by SKR in 2009-10, animal 2 densities were higher than all previous years at 30.2 and 47.1 SKR/ha, which is considered “high” for this species (Tetratech and SJM Biological Consultants 1999). The positive trend suggests a continued pattern of high survivorship and colonization of SKR in the high suitability stratum This was the first year we were able to analyze all of the data in a multi-state framework and established th