CAREER: Morphology, performance, and ecology of the endangered salt marsh harvest mouse and co-occurring wetland rodents

Understanding why a species is endangered is critical to planning for its recovery. Combining work in the field and in the laboratory, this study investigates the endangered salt marsh harvest mouse, endemic to the San Francisco Bay estuary, and how it is physically adapted to its wetland environment. Occupying habitats that experience natural and controlled flooding on daily and seasonal bases, individuals of this species are subjected to continual environmental challenges that impact their behavior.

Yet little is known about how they manage to forage, survive, and reproduce. Furthermore, these endangered mice often share these habitats with other rodents, and it is not clear how or whether they avoid competing with them. To advance our understanding of the ecological and evolutionary challenges of this endangered species, and other related species, this project investigates how individuals perform basic functions of biting, climbing, and swimming as they relate to foraging and moving through their habitats.

Because these functions are influenced by anatomy, differences in important aspects of their body form are analyzed, such as tail and limb lengths, foot pad size and shape, and head width and depth. The relationships between performance and body form provide insights into how and why physical differences among species have evolved. Understanding variation in form and function is imperative for predicting long-term success of salt marsh harvest mouse in response to habitat management practices and sea level rise associated with climate change.

A new field course centered on the ecology of the Suisun Marsh, California, will be implemented to teach students marketable field and quantitative skills, to contribute data to the research project, and to instill an understanding and appreciation for the ecological roles of rare and endangered species.

This study integrates morphology, biomechanics, ecology, and genetics to examine the ecological implications of differences in morphology and performance among the endangered salt marsh harvest mouse and other co-occurring wetland rodents. The proposed morphological and kinematic analyses of feeding- and locomotor-related behavior, performed in the laboratory, will provide insights into how salt marsh harvest mice and other wetland rodents navigate potentially conflicting demands of their diverse substrates and how they partition resources.

The lab-based performance studies are complemented by work in the field that address the adaptive value of the traits: long-term mark-recapture studies, quantification of microhabitat characteristics, and genetic analyses. Integrating basic science and wildlife management objectives, this work has the potential to inform wildlife management policies by (1) identifying limitations to the salt marsh harvest mouse’s physical abilities to use microhabitat and food resources and (2) illuminating the adaptive consequences of different wetland management regimes.

California State University San Marcos (CSUSM) is a Hispanic Serving Institution with a strong tradition of involving underrepresented students in all levels of academic research. Each of the study dimensions (morphology, performance, ecology, and genetics) encompasses the scope of a master’s thesis project, and funding will be provided for several graduate students.

Moreover, CSUSM undergraduate students will be educated on the study’s foundational material in the newly proposed field ecology course. Beyond research and education, this project has the capacity to reach hundreds more, both inside and outside of the scientific community, through conference presentations, scientific publications, media interactions, and community STEM outreach activities highlighting the importance of native fauna.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.