We undertook a 2-year (2002)(2003)(2004) mark-recapture study to investigate demographic performance and habitat use of salt marsh harvest mice (Reithrodontomys raviventris halicoetes) in the Suisun Marsh. We examined the effects of different wetland types and microhabitats on 3 demographic variables: density, reproductive potential, and persistence. Our results indicate that microhabitats dominated by mixed vegetation or pickleweed (Salicornia spp.) supported similar salt marsh harvest mouse densities, reproductive potential, and persistence throughout much of the year, whereas few salt marsh harvest mice inhabited upland grass-dominated microhabitats. We found that densities were higher in diked wetlands, whereas post-winter persistence was higher in tidal wetlands, and reproductive potential did not differ statistically between wetland types. Our results emphasize the importance of mixed vegetation for providing adequate salt marsh harvest mouse habitat and suggest that, despite their physiognomic and hydrological differences, both diked and tidal wetlands support salt marsh harvest mouse populations by promoting different demographic attributes. We recommend that habitat management, restoration, and enhancement efforts include areas containing mixed vegetation in addition to pickleweed in both diked and tidal wetlands.

No abstract

The salt marsh harvest mouse (SMHM, Reithrodontomys raviventris) is an endangered species, endemic to the San Francisco Estuary. Despite being protected for almost half a century and being included in a large number of recovery, restoration, and management plans, significant data gaps hinder conservation and management of the species, a challenge further complicated by developing threats such as climate change. In this review, we present the current state of knowledge; highlight research gaps on habitat requirements and distribution, taxonomic status and genetic structure, physiology, reproduction and demographics, population dynamics, and behavior and community interactions; and present an overview of threats to the species. Our review indicates that substantial data gaps exist; although some aspects of SMHM ecology, such as habitat use, have been addressed extensively, others, such as the effects of environmental contamination, are largely unaddressed. We suggest that conservation and restoration-planning processes consider experimental approaches within restoration designs to address these deficiencies. Continued investment in basic and applied SMHM ecology to collect baseline and longterm data will also be beneficial. Additionally, further coordination among managers and researchers can facilitate more effective responses to uncertainties and emerging threats, especially climate change, which threatens the SMHM and its habitat throughout its range.

The northern subspecies of the salt marsh harvest mouse (Reithrodontomys raviventris halicoetes) is morphologically similar to the western harvest mouse (R. megalotis) with which it co-occurs in the Suisun Marsh, California, USA, and therefore they are difficult to distinguish in the field. The salt marsh harvest mouse is a federal and California state-listed endangered species, whereas the western harvest mouse has no special status. Thus, our objective was to identify the most effective field metrics that distinguish the species. First we identified a barcode of life and restriction fragment length polymorphism approach for genetically distinguishing between the species. Then we performed univariate tests to examine variation in standard external morphological traits within and between species, and found that differences between species were confounded by sex and age. We then used discriminant function analysis and multiple logistic regression (MLR) to find combinations of characters that resulted in the highest percentages of correct classification based on a data set of individuals with genetically verified species identity. The best model (MLR) correctly classified 90.1 AE 3.5% ( x AE SD) of individuals, though all approaches performed relatively poorly with smaller, ostensibly younger, mice. Therefore, tail length, body length, and tail diameter, if treated in a comprehensive multivariate context, can yield substantial accuracy for distinguishing between coexisting northern salt marsh and western harvest mice. Ó 2018 The Wildlife Society.KEY WORDS discriminant function analysis, field identification, multiple logistic regression, Reithrodontomys, salt marsh harvest mouse, Suisun Marsh, western harvest mouse.