Fieldwork starts tomorrow!

The following is a summary of my current research and other good things to know before reading the daily blogs.

Introduction

            A current conservation concern is the loss of biodiversity worldwide ( Ehrlich & Wilson, 1991; Dirzo & Raven, 2003), and one factor is the urbanization of aquatic ecosystems (Walsh et al., 2005). For example, urban waterways, when compared to ones in wildlands, have a notably lower diversity of benthic macroinvertebrates (BMI) and filamentous algae (Paul & Meyer, 2001). In wildland waterways both filamentous algae and BMI are the principal food resources of the western pond turtle, Emys marmorata (R. B. Bury, 1986). Already many E. marmorata are living in urban waterways and it is likely even more will be doing so (B. Bury & Germano, 2008). This is because urbanization continues to spread throughout its range along the Pacific Coast of the continental United States ( Theobald, 2005; Radeloff, Hammer, & Stewart, 2009). The focus of my research is how living in urban waterways may affect the diet and feeding ecology of E. marmorata. To describe the affect of urbanization on their diet and feeding ecology, I am comparing my results with those from a similar study done in wildlands (R. B. Bury, 1986). 

              Because I plan to publish my research, this work can contribute to our overall knowledge of the natural history of E. marmorata and the affect of urbanization on its diet and feeding ecology. In addition, it may be valuable to wildlife agencies since E. marmorata has a listed conservation status throughout its range (Rosenberg, Gervais, & Vesely, 2009). Finally, the improved methods I have devised for getting stomach content samples may be useful to other wildlife researchers.

Methods        

            I am collecting research data from aggregations of E. marmorata in Santa Rosa, California, during the months when they are most actively feeding (May-August). To describe their diet, I get stomach content samples by using a revised stomach flushing procedure that enhances the efficacy and safety of previous methods. It includes a sophisticated anesthesia protocol that reduces anxiety and pain while decreasing the possibility of physical injury to the alimentary canal. Afterwards, because the anesthesia is rapidly reversible, the subjects regularly return to their foraging pools within six hours rather than the twenty-four hours that were previously required. Because of the extensive laboratory and field-testing I did, this procedure has the approval of the Sonoma State University Institutional Animal Care and Use Committee and the California Department of Fish and Game.

            To describe their feeding ecology I am inventorying both urban waterways for available food resources by collecting samples using customary equipment and procedures (e.g., D-nets, activity traps, and Hester-Dendy samplers). Regardless of the collection technique, I handle all samples in a similar fashion. I use traditional laboratory protocols and equipment for the identification of BMI and algae in each sample. For example, I use a stereoscopic dissecting microscope to sort all samples into distinct elements (i.e., body parts, or discrete organisms) and identify each sample to the lowest possible taxonomic level.

        Lastly, while I am in the field I am taking observation notes using the Joseph Grinnell methodology (Griesemer, 1990) that includes information I get by using contemporary tools (e.g., GPS combined with digital photography).

Preliminary Results

            There are differences between the diet of E. marmorata living in urban waterways and those living in wildlands. First, all of the urban E. marmorata are apparently carnivorous, a departure from the omnivorous diet of those living in wildlands. In addition, the diet of E. marmorata in urban aquatic ecosystems is less diverse than that of E. marmorata living in wildlands have. Specifically, in wildlands E. marmorata have eighteen food groups in their diet while those in Brush Creek have seven groups; in Santa Rosa Creek they have two groups. Next, E. marmorata in Santa Rosa Creek generally eat crayfish, while in wildlands crayfish comprise less than one percent of their diet; none were found in samples from Brush Creek.

            In addition, some of my tangential observations are interesting and may be worth investigating. Some samples from Brush Creek had freshly cut leaf tips filled with the larvae of a terrestrial fly (Agromyzidae). Thus, E. marmorata may be targeting vegetation filled with an animal food resource inside, a common foraging behavior. This is not surprising since I do find these larvae in low overhanging vegetation can a that at times be submerged. Next, since E. marmorata largely eat crayfish in Santa Rosa Creek they may be competing with the North American river otter, Lontra canadensis for food. Based on my observations and scat examinations, L. canadensis appear to also rely on crayfish as their main food resource. Lastly, since the beginning of this study, human disturbance is increasing in the channel of Santa Rosa Creek as well as along its banks. 

Santa Rosa Creek during sediment removal 2012.

Santa Rosa Creek sediment removal 2012.

Staffing

         Until the end of last week, I did not have a reliable assistant to help me. A former undergraduate and soon to be graduate colleague offered to help me this summer. THANK YOU KATE!!! She brings with her a wealth of information and has a good background in fieldwork. She can handle the rough terrain, the prickly vegetation, and other challenges of my work. 

Kate baiting and setting a hoop trap.

          Overall, I am sanguine that this field season will be the most productive I have had!

Bibliography

Bury, B., & Germano, D. (2008). Conservation Biology of Freshwater Turtles and Tortoises. (A. Rhodin, P. Pritchard, P. P. van Dijk, & R. Saumure, Eds.)Chelonian Research Monographs, 5, 001.1–001.9. Chelonian Research Foundation. doi:10.3854/crm.5.001.marmorata.v1.2008

Bury, R. B. (1986). Feeding Ecology of the Turtle, Clemmys marmorata. Journal of Herpetology, 20(4), 515–521.

Dirzo, R., & Raven, P. H. (2003). Global State of Biodiversity and Loss. Annual Review of Environment and Resources, 28(1), 137–167. doi:10.1146/annurev.energy.28.050302.105532

Ehrlich, P. R., & Wilson, E. O. (1991). Biodiversity Studies: Science and Policy. Science, 253(5021), 758–762.

Griesemer, J. (1990). Grinnell Method - Griesemer 1991 PSA 1990-v2-79-93 Material Models in Biology. PSA: Proceedings of the biennial meeting of the Philosophy of Science Association. Retrieved February 26, 2012, from

Paul, M. J., & Meyer, J. L. (2001). Streams in the Urban Landscape. (J. L. Meyer, Ed.), 1–35.

Radeloff, V. C., Hammer, R. B., & Stewart, S. I. (2009). The Wildland-Urban Interface in the United States. Ecological Applications, 15(3), 799–805. Retrieved from  http://www.jstor.org/stable/4543395 .

Rosenberg, D., Gervais, J., & Vesely, D. (2009). Conservation Assessment of the Western Pond Turtle in Oregon (Actinemys marmorata). Executive Summary, 1–80.

Theobald, D. M. (2005). Landscape Patterns of Exurban Growth in the USA from 1980 to 2020. Ecology and Society, 10 (1)(32), 1–34. Retrieved from http://www.ecologyandsociety.org/vol10/iss1/art32/

Walsh, C. J., Roy, A. H., Feminella, J. W., Cottingham, P. D., Groffman, P. M., & Morgan, R. P., II. (2005). The Urban Stream Syndrome: Current Knowledge and the Search for a Cure. Journal of the North American Benthological Society, 24(3), 706–723.