I am a conservation ecologist and an Associate Professor at San Diego State University. I also serve as Director for the Institute for Ecological Management and Monitoring, a multi-disciplinary research institute at SDSU. I received my Bachelor’s degree from Vassar College and went on to complete my doctorate in Ecology at the University of California, Davis Using innovative field, quantitative and lab-based approaches, my research focuses on vulnerable wildlife populations that live in both terrestrial and aquatic environments and face pressing conservation issues, e.g. fragmentation, habitat loss, harvest and incidental mortality, disease and other disturbances. Over the past decade, I have been spearheading integrative research in conservation ecology, policy and resource use, with expertise and experience across a wide taxonomic range of organisms. I has served as leader of several research initiatives designed to develop new tools and methodological approaches to understand the magnitude and extent, of population-level and landscape level effects of human-mediated activities.
Members of the Lewison Conservation Ecology Lab work on a variety of taxa using a wide range of methodologies. What unites the lab is a dedication to understanding the impacts of human interaction and disturbance on vertebrates of conservation concern. Below are some of our general research interests and links to projects in the lab.
Fisheries and bycatch
In the past 50 years, total world fisheries production has increased steadily from 19.3 million tons in 1950 to more than 154 million tons today. Beyond direct effects of fish removal, fishing also leads to incidental capture of non-target species, termed bycatch. Bycatch species can be species of conservation concern (e.g. marine mammals, sea turtles, seabirds) or commercially viable non-target species, e.g. sharks. Fisheries bycatch is one of the primary causes of observed declines of seabirds, marine mammals, sharks and large predatory fishes, collectively termed marine megafauna. For some depleted species, such as Pacific leatherback (Dermochelys coriacea), vaquita (Phocoena sinus), and the Atlantic humpbacked dolphin (Sousa teuszii), fisheries bycatch has been identified as the single largest threat to extant populations. Characterizing and quantifying bycatch and bycatch limits presents a formidable challenge and is the focus of a number of research projects in the Lewison lab.
Ecotoxicology and ecosystem health
Ecotoxicology is the multidisciplinary study of the effects of toxic chemicals on biological organisms, especially at the population, community, and ecosystem levels. The ultimate goal of this field is to predict the effects of pollution so proactive approaches may be taken to prevent or remediate detrimental effects. In ecosystems already impacted by pollution (i.e. San Diego Bay), ecotoxicological studies can inform the best course of action to restore ecosystem services and functions efficiently and effectively. Members of the Lewison Lab collaborate with Dr. Eunha Hoh in the Graduate School of Public Health to address toxicological impacts to vulnerable vertebrates.
Characterizing the spatial and temporal utilization of habitat by organisms is fundamental aspect of conservation ecology. By studying habitat utilization researchers are able to gain insights into resource use and requirements, behavior, inter and intra-speciific interactions, protected area design, and numerous other factors that are necessary to designing effective wildlife management and conservation strategies. Species’ habitat utilization can be studied via direct observations and remote sensing technologies (e.g. satellite telemetry), which can then be combined with data on environmental factors to describe and predict habitat use patterns.
Understanding how fragmented populations are connected is important for effective management and conservation. Connectivity can refer to either the movement of individuals from one habitat to another or the movement of genes through adjacent populations, commonly referred to as gene flow. Since animal movement and gene flow can be difficult to observe, scientists have developed multiple tools to empirically test for connectivity including both telemetry and genetic analyses. Telemetry employs the use of radio, acoustic, and satellite tags to monitor animal presence and movement. Genetics techniques allow researchers to compare the DNA of individuals in different potential populations to test whether there is likely any genetic exchange among them.
Trophic ecology refers to the feeding relationships of an organism within an ecosystem. Determining the trophic dynamics and interactions of organisms generates an overall understanding of an organism’s role in ecosystem function and nutrient flow processes. Many animals exhibit complex life histories and cryptic behavior which make it difficult to study their trophic interactions. Tools such as stable isotope analysis allow us to investigate the trophic ecology of many animals in order to understand their habitat use, role in mediating nutrient flow, trophic status, critical habitat and migratory habits all of which contribute to developing more effective management and conservation efforts.
Shaffer, S.A., Cockerham, S., Warzybok, P., Bradley, R.W., Jahncke, J., Clatterbuck, C.A., Lucia, M., Jelincic, J.A., Cassell, A.L., Kelsey, E.C., Adams, J. 2017. Population-level plasticity in the foraging behavior of western gulls (Larus occidentalis). Movement Ecology, doi: 10.1186/s40462-017-0118-9.
Clatterbuck, C.A., Lewison, R.L., Dodder, N., Zeeman, K., Schiff, K. 2018. Seabirds as regional biomonitors of legacy toxicants on an urbanized coastline. Science of the Total Environment, 619-620C, 460-469.
Gaos, A., Lewison, R.L; Jensen, Michael; Liles, Michael; Henriquez, Ana; Chavarria, Sofia; Pacheco, Carlos Mario; Valle, Melissa; Melero, David; et al.Rookery contributions, movements and conservation needs of hawksbill turtles at foraging grounds in the eastern Pacific Ocean. Marine Ecology Progress Series, in press.
Tredick, C., Lewison, R.L., Deutschman, D. et al. 2017. A Rubric to Evaluate Citizen Science Programs for Long-Term Ecological Monitoring. Bioscience, Vol. 67 No. 9.
Scales, K. et al. 2018. Fit to predict? Ecoinformatics for predicting the catchability of a pelagic fish in near real-time. Ecological Applications,10.1002/eap.161.
Gaos, Alexander; Lewison, Rebecca; Jensen, Michael; Liles, Michael; Henriquez, Ana; Chavarria, Sofia; Pacheco, Carlos Mario; Valle, Melissa; Melero, David; et al. 2017. Natal foraging philopatry in eastern Pacific hawksbill turtles. Royal Society Open Science, 4: 170153. http://dx.doi.org/10.1098/rsos.170153.
Drake, Kristina, Bowen, Lizabeth, Lewison, Rebecca; Esque, Todd; Nussear, Kenneth; Braun, Josephine; Waters, Shannon; Miles, A. 2017. Coupling gene-based and classic veterinary diagnostics improves interpretation of health and immune function in the Agassiz’s desert tortoise (Gopherus agassizii). Conservation Physiology, Volume 5, 10.1093/conphys/cox037.
Lewison, R.L., An, L., Chen, X. 2017. Reframing the PES framework in a coupled human and natural systems context. Ecosystem Health and Sustainability, in press.
Beaulieu, N. E., Sherman, K. K., Trego, M. L., Crocker, D. E., Kellar, N. M. Initial Validation of Blubber Cortisol and Progesterone as Indicators of Stress Response and Maturity in an Otariid; The California Sea Lion (Zalophus californianus). General and Comparative Endocrinology, in press.
Kellar, N. M., Speakman, T. R., Smith, C. R. , Lane, S. M., Balmer, B. C., Trego, M. L., Catelani, K. N., Robbins, M. N., Allen, C. D., Wells, R. S., Zolman, E. S., Rowles, T. K., Schwacke, L. H. 2017. Low reproductive success rates of common bottlenose dolphins (Tursiops truncatus) in the northern Gulf of Mexico following the Deepwater Horizon disaster (2010-2015). Endangered Species Research, 33:143-158. https://doi.org/10.3354/esr00775.