DEMOGRAPHY OF THE SALT MARSH HARVEST MICE AND ASSOCIATED RODENTS IN TIDAL AND MANAGED WETLANDS
Katie R Smith; WRA / UC Davis; 805 S Eliseo Drive, Kentfield, CA, 94904; (530) 400-7729; RATSMITH@UCDAVIS.EDU; Laureen-Barthman Thompson, Sarah Estrella, Melissa K. Riley, Sadie Trombley, Candice Rose, Douglas A. Kelt
Suisun Marsh is the largest contiguous marsh remaining on the West Coast of the United States, and makes up approximately 10% of the wetlands remaining in the San Francisco Estuary. The Suisun Marsh was safeguarded from development primarily through the operation of over 100 privately owned and operated waterfowl hunting clubs, which manage for diked, ponded waterfowl habitat. However, this management and the subsequent loss of tidal influence on these ponds has been considered harmful for some species, including the federally endangered salt marsh harvest mouse (Reithrodontomys raviventris). To determine the value of tidal wetlands relative to those managed for waterfowl, we performed periodic surveys for rodents in paired managed and tidal wetlands over five years, and utilized a robust design capture-mark-recapture analyses to estimate demographic parameters and abundance for the three most common rodents in the Suisun Marsh – the northern salt marsh harvest mouse (R. r. halicoetes), the western harvest mouse (a sympatric native species; R. megalotis) and the house mouse (a sympatric non-native species; Mus musculus). Wetland type had no effect on detection, temporary emigration, or survival for any of these species. However, fecundity and population growth for all three species were affected by an interaction of season and wetland type, although none of these species was consistently superior in either habitat type in all seasons. Estimated abundance of salt marsh harvest mice and house mice were similar in both wetland types, whereas western harvest mice were more abundant in managed than tidal wetlands. Salt marsh harvest mice also showed no affinity for any microhabitat characteristics associated with tidal wetlands. Managed wetlands in Suisun Marsh support salt marsh harvest mice and house mice equally in terms of key demographic parameters and abundances, and abundances of western harvest mice were greater in managed wetlands, suggesting that managed wetlands may be superior in terms of supporting native rodents overall. As climate change and associated sea level rise is predicted to threaten coastal marshes, these results suggest that a proactive management strategy for salt marsh harvest mice should include development of managed wetlands such as those documented in Suisun Marsh.
Ecology and Conservation of Amphibians and Reptiles I