SALT MARSH HARVEST MICE (REITHRODONTOMYS RAVIVENTRIS) DISTRIBUTION, ABUNDANCE, AND POPULATION TRENDS IN THE EAST BAY REGIONAL PARK DISTRICT

David L Riensche; East Bay Regional Park District; driensche@ebparks.org; Brooke E. Wainwright, Erica M. Rutherford, Sarah C. Gidre

The Salt Marsh Harvest Mouse (Reithrodontomys raviventris) is a state and federally listed endangered species endemic to the salt marshes of the San Francisco Bay Area. As a result of anthropogenic change, its pickleweed-dominated tidal marsh habitat has been greatly reduced. The East Bay Regional Park District manages 40 miles of shoreline, which includes viable Salt Marsh Harvest Mouse habitat. The District surveyed five sites for Salt Marsh Harvest Mice between 2012 and 2015. A total of 47 Salt Marsh Harvest Mice were captured, with a total population index of 1.36 (individuals/trap nights x 100). There was no significant correlation between captures and pickleweed height and coverage; however, populations differed significantly among sites and a simple linear regression analysis of captures by year showed a significant decline. Continued monitoring is necessary to determine what the potential drivers might be producing these observed trends.