San Clemente Island (SCI) is a U.S. Navy-owned island composed primarily of maritime desert scrub and invasive grassland vegetation communities. There are two species of mice on SCI; the endemic deer mouse (Peromyscus maniculatus clementis) and the introduced house mouse (Mus musculus). Both species are a food source for endemic predators including the island fox (Urocyon littoralis clementae), loggerhead shrike (Lanius ludovicianus mearnsi) and raptors. We have used capture-recapture data to calculate density for both mouse species since 2015. In late-July 2024, a wildfire burned approximately 25% of SCI’s land area including one of our mouse sampling trap grids. Because no grid had previously burned, this fire provided an opportunity to examine the effects of wildfire on SCI’s mouse population. We conducted capture-recapture sampling one month after the fire over 245 trap nights. Density of deer mice remained stable and house mice increased one month after the fire compared to sampling conducted 3-weeks prior to the fire. Further capture-recapture sampling will be conducted to determine long-term effects of fire including the impact of increased fuel load densities and how these factors influence mouse densities. These results help us better understand fire vulnerability for these key species.

A group of dedicated MGS scientists formed a new non-profit in 2023 with the mission of ensuring the continued survival of the state threatened Mohave ground squirrel. With two grants (CDFW Watershed Branch and WCB) in hand, a collaboration of federal, state and local parners was formed and a large scale project for long-term monitoring of the species was underway in 2024. We are here to report on progress on our first year of innovative field studies anmd our innovative collaboration, the key to our sucess.

Shrews (Sorex spp.) have not been well studied, partly because they are difficult to capture and can die quickly due to their fast metabolism, high protein needs, and small body mass. There are two species of Sorex that are of conservation concern in the San Francisco Bay: salt-marsh vagrant shrew and Suisun wandering shrew. Aside from some documentation on the California Natural Diversity Database, there is sparse research on population densities, movements, or presence of these species. A novel method of collecting fecal samples recently developed for detection of salt marsh harvest mouse (SMHM) DNA has also been used to collect fecal samples from other small mammals to genetically identify presence. We partnered with land owners to identify the potential presence of SMHM and shrews within Suisun Bay. We used bait stations to passively collect feces. Then, we used previously developed genetic analyses to identify rodents and developed a new set of DNA primers to detect the presence of shrews in the pooled sample. We identified the presence of shrews across three sites. The results demonstrate the effectiveness of our method for surveying shrews and has potential to positively impact shrew conservation efforts by enabling safe and effective population monitoring.

A sizable knowledge gap exists regarding ecological interactions of the Buena Vista Lake shrew (Sorex ornatus relictus), a federally endangered small mammal endemic to the San Joaquin Valley of California. No studies have examined the effect of abiotic factors on S. o. relictus activity patterns. To deepen our knowledge of S. o. relictus and identify potential challenges to their persistence, I used camera trap data collected at four sites in the southern San Joaquin Valley between 2016 and 2020 to associate the occurrence of S. o. relictus at bait stations with corresponding abiotic conditions. I determined that ambient air temperature was the most supported variable to predict the presence or absence of S. o. relictus at bait stations. An inverse association exists between S. o. relictus presence and ambient air temperature, where the predicted probability of shrew presence increased as air temperature decreased. My results can potentially inform a reevaluation of the air temperature parameters in the current survey protocol for detecting S. o. relictus presence. Doing so may increase the probability of detecting S. o. relictus, a critical component of conservation efforts, and aid the well-being of an endemic, endangered subspecies.

The Carrizo Plain is one of the largest relatively intact portions of the San Joaquin Desert, and hosts high levels of endemic species threatened by habitat loss and other anthropogenic impacts. The giant kangaroo rat (Dipodomys ingens) is at the center of this ecosystem, but management for this and other endangered species is complicated by multiple use mandates. Previous research has presented sometimes conflicting results on the interactions between domestic cattle and giant kangaroo rats, so in collaboration with the Nature Conservancy, California Department of Fish & Wildlife, and the Bureau of Land Management, the Carrizo Plain Ecosystem Project (CPEP) was established to better understand these interactions. Here we will present our findings after monitoring kangaroo rat populations on the Carrizo Plain for 18 years at 30 replicated study plots with or without grazing exclosures, with an emphasis on elucidating the long-term relationship between cattle grazing and giant kangaroo rat populations. Though the impacts of low-intensity grazing on Giant Kangaroo Rats may be small in magnitude, they are important to understand in the face of challenges such as limited habitat and increased climactic variation to inform future land management decisions.

The narrow-faced kangaroo rat (Dipodomys venustus) is a highly understudied Heteromyid species endemic to the central coast of California, with three currently recognized subspecies. All three subspecies are on the California Department of Fish and Wildlife special animal list and the Santa Cruz kangaroo rat (D. v. venustus) is considered critically imperiled - though this designation offers no formal protection. It is likely that the narrow-faced kangaroo rat has engineering/keystone effects via scatter hording seed caching, and the creation of complex burrow systems. Before management action can be taken, more information is needed on population trends, habitats associations, and sub-species taxonomic status. Using genetics to inform species and subspecies ID, we created a range-wide Maxent Habitat Suitability model. We then created a habitat Suitability Model for each confirmed subspecies and compared any differences caused by local adaptation. The results of this study will help managers make informed decisions on the population (and endangerment) status of each subspecies and provide updated tools and methods for the conservation of the species.

The Buena Vista Lake ornate shrew (Sorex ornatus relictus; BVLOS) is a federally endangered subspecies of shrew endemic to the southern Tulare Basin, California. BVLOS are typically associated with wetland habitats and moist soils. Kern National Wildlife Refuge (KNWR) has documented BVLOS across its wetland habitats since 1992, but several observations of the species in alkali desert scrub habitat during recent exploratory surveys exposed a need for more information on the relationship between BVLOS presence and distance to water. The objective of this study was to collect a year-round dataset of shrew activity at varying distances from water to discern seasonal differences in habitat associations and water dependence using remote cameras. 36 cameras were deployed across KNWR’s upland habitat beginning in April 2024 and locations were stratified by distance to water. As of October 2024, seven sites have had BVLOS detections with the farthest detection being 1583 m from water. Using a single-season, single-species occupancy model, we aim to assess the effect of microhabitat characteristics on occupancy. Our results may reveal what habitat characteristics are most important to BVLOS, how distribution varies seasonally, and how to better manage for a species that could be more widespread than previously thought.

Recently it has become clear that habitat use by the salt marsh harvest mouse is quite flexible. But that begs the question, if SMHM do not REQUIRE pickleweed, why are they mostly restricted to marsh habitat? And why are SMHM abundant in marshes during some years, and rare during other years? And what about all those other rodents we catch? These are the kinds of questions that can only be answered with long term, comprehensive datasets collected during periods of diverse conditions. The most comprehensive multi-year study in the last decade occurred only during drought conditions, which was great for looking at the impacts of habitat and competition, but not at teasing out the impacts of other environmental factors, most importantly, precipitation. An inability to account for weather has hindered our ability to evaluate historical datasets, but data collected in the past five years has begun to illuminate the impacts of precipitation, revealing that some substantial impacts of wet winters may not be realized until over a year later. Even more interestingly, those impacts seem to be influenced by competition, by way of habitat. Here we present the interaction between weather, habitat, and competition, and discuss impacts on SMHM conservation.