Colvin Winners Conduct Fieldwork in Africa
From top to bottom: A picture of the tent where Chambliss and Walker stayed; a close-up of S. volkensii with a trowl for scale; patch and root structure of S. volkensii (Photos: Sarah Chambliss); Walker being liced by one of the cows (Photo: Allison Tracy); cattle sleeping after being dipped; cattle walking to water, the land is overgrazed and so this area is basically now just dirt with no grass. (Photos: Josephine Walker)
In May 2009, juniors Sarah Chambliss ’10 and Josephine Walker ’10 were named co-recipients of the 2009 Becky Colvin memorial award. The award was established in 1995 by Dr. and Mrs. Robert Colvin in memory of their daughter, Becky Colvin ’95. Becky was an ecology and evolutionary biology major who was committed to field research. Each year, the fund supports environmental field research projects associated with the recipients’ senior theses. Last summer both of the recipients conducted research in Africa.
Sarah Chambliss ’10
Proposed senior thesis title: “Rangeland Degradation and Changes in Plant Communities: Understanding the case of S. volkensii, a native plant spreading in Kenya.”
What project did you work on last summer as a Colvin winner? My project looked at a littlestudied species of native plant called S. volkensii. It grows in the semi-arid rangelands of Kenya, and it seems to spread prolifically in land that is overgrazed and degraded, covering large areas in thick patches.
Local pastoralists worry about its spread, since their livestock cannot eat it and cannot get to the grass within the patches. They have never seen it spread to this extent, and they are unsure what consequences S. volkensii will have on their land.
What did you study? In my research, I wanted to study the way that this plant spread into new areas and try to pinpoint the reasons that it is now growing out of control when it had previously existed in balance with other plants.
What were your findings? I conducted my research at the Mpala Research Center near Laikipia, Kenya. Since I was only in Kenya for six weeks over the summer, my findings were limited to the information I could gather in that time; I couldn’t revisit the same patches after they had grown and re-measure them. Although I would have liked to see how the patches grew and proliferated over time and whether they changed the soil or plant communities around them, I couldn’t observe that directly. Instead, I took census-type data on about 300 individual patches. I found that patches tend to grow under Acacia trees, probably taking advantage of the higher water and nutrients under their canopy. Since the spread of trees and shrubs often follows overgrazing, the spread of S. volkensii might be related to that trend.
What surprised you the most about your results or experience? Doing fieldwork in the African bush has its inherent difficulties, and can be somewhat chaotic. Thanks to my advisors, Professor David Wilcove and Dr. Elizabeth King, I was prepared for these challenges and had worked out a thorough but flexible research plan before I got to Kenya. However, there were still some factors I had not prepared for: two of my sampling sites were a favorite hang-out spot for a family of elephants, and I frequently had to adapt my daily research plan to stay out of their way.
What did you learn by conducting field research? Throughout the course of my research I learned how far ahead you have to look in order to find real results when your time to do fieldwork is limited. My advisor required me to have my methods (including the statistical tests I would use on my data) worked out before I began gathering data. At the time, I thought it was premature, but I see now how my project could have gotten completely derailed if I hadn’t prepared in this way.
Are you working toward a Certificate in Environmental Studies? I am working toward an ENV certificate — I really like the program and the interdisciplinary approach it takes in confronting environmental issues. I’ve really enjoyed the wide variety of courses that I’ve been able to take to get my certificate, and I definitely have a broader perspective than if it had been only environmental science.
How do you hope your thesis research will have an impact? I hope that pastoralists whose livelihoods are threatened by S. volkensii and other ranch managers will benefit from the results of my research, although I’m not sure whether the information will get to them. Dr. King, a post-doc in the ecology and evolutionary biology department, also works with the plant and has a close relationship with local pastoralists in the area we studied, so by helping her research I can hopefully have an impact.
Will your experiences as a Colvin winner influence your plans after graduation in June? My experiences doing field research, made possible by the funds I received from the Becky Colvin grant, did make an impression on me, and I have applied for many positions doing field research on plants and doing environmental modeling. My plans for next year are still unresolved, but I hope to find a job that will allow me to continue to work in the field, which is what I really love doing.
Josephine Walker '10
Proposed senior thesis title: “The Impact of Acaricide Use on Theileria parva infection in Cattle and Buffalo in Kenya.”
Please briefly describe your project and the goals of your thesis. For my thesis, I am studying a tick-borne disease that affects both cattle and wildlife in Africa. The cost of tick-borne diseases has been estimated to be $7 billion/year globally, and they also limit the development of the livestock industry.
The pathogen I’m studying is Theileria parva and it causes several different clinical manifestations including East coast fever and Corridor disease. T. parva is an economically important disease and there is no feasible vaccine available, so most cattle owners “dip” their cattle in chemicals to kill the ticks (acaricides) in order to prevent the animals from getting the disease.
Dipping is known to cause many problems. The cattle ingest the chemicals when they groom themselves and each other, and it makes them tired so that they graze less, which can be problematic in the frequent times of drought when they need every bite just to stay alive. Depending on the chemical used, residues may accumulate in the milk and meat that is sold or that their owners rely on for sustenance. Dipping also contributed to the decline of oxpecker birds which eat ticks off of grazing animals, possibly through bioaccumulation of the chemicals. Some of the chemicals historically used as dips include arsenic and DDT. Ticks also evolve resistance to the chemicals, and new strategies need to be developed to keep up.
There’s another potential effect of dipping that hasn’t previously been considered, and that is what I am investigating for my thesis. Frequent dipping reduces the level of ticks in the environment, and this could impact the epidemiology of the disease and potentially make disease outbreaks in wildlife or cattle more severe. In buffalo populations in East Africa, normally all or almost all animals are infected with Theileria parva at a young age and so develop resistance to the disease, they show few clinical signs of carrying the pathogen. This is known as enzootic stability, and it indicates an evolved state where the pathogen coexists with the host and the tick vector. When tick populations are reduced, it could reduce the rate of infection in buffalo so that the animals do not develop resistance at a young age. This would mean that when the pathogen is introduced, it causes devastating outbreaks. Enzootic stability is also possible in native breeds of cattle, but frequent dip use has meant that cattle do not have any resistance to the disease. If dipping is interrupted, as it has been historically in cases of civil war or political unrest, then sudden exposure to the disease can lead to the loss of large numbers of livestock.
For my thesis, I am using a mathematical model to investigate the threshold tick level necessary to maintain enzootic stability and examining the impacts of reduced tick levels on the disease in both cattle and buffalo. To answer these questions, I gathered data on environmental tick levels, tick numbers on cattle, and disease presence in the cattle and ticks on ranches that dip at different frequencies. I will use parameters from my data collection and from the literature to develop my theoretical model. From this, I will be able to make management suggestions regarding the impact of dipping, especially in areas where the cattle industry is balanced with ecotourism and wildlife conservation.
Were you able to accomplish what you originally intended, or did the project change once you began working on it? My project definitely developed over time. Initially I thought I would investigate several tick borne diseases and be able to gather data on more ranches than I did. I also thought I’d be able to count every tick on each cow. Considering I found more than 100 ticks in just one ear on some cows, that definitely didn’t turn out to be a possibility. The final project design happened on the ground in Kenya and it ended up coming down to feasibility and time constraints. I think it’s better that way, because in the end a more focused project will allow me to make relevant management recommendations.
What surprised you the most about your results or experience, and what did you learn? I am excited and pleased by my results so far, especially about the fact that I have results and that preliminary analysis suggests that my hypothesis is supported (although I haven’t completed my model yet). My experience was really amazing and I learned so much — especially about the way that field research actually works. I had to be incredibly flexible and constantly planning and re-planning through many logistical obstacles including trying to use 4 different broken down cars and the presence of dangerous animals around the cattle herds. I was surprised by how physically draining it is to walk all day in the equatorial sun, and how easily I got used to handling ticks and dung. Despite all the challenges, I found out that I really love fieldwork, and being in Kenya was incredibly rewarding intellectually and emotionally. I can’t wait to go back, and to continue to do research throughout my career.
Are you working toward an ENV Certificate? I am getting an ENV certificate as well as an African Studies certificate. Working towards an ENV certificate allowed me to take a really interesting breadth of courses beyond my EEB classes, including courses on environmental policy and engineering. I really appreciate the interdisciplinary nature of the ENV certificate. Although it’s possible for an EEB major to take a lot of departmentals that are cross-listed with ENV, in order to complete the certificate it’s necessary to branch out and take courses that you otherwise might not have considered.
Do you hope your research will have an impact in Kenya? Based on the results of my project, I hope to develop management recommendations for cattle ranchers in Kenya. Many ranchers balance cattle production with ecotourism and wildlife conservation, so it will be helpful to see how their strategies involving cattle impact wildlife indirectly. Also, I think most people dip because that’s what they know works and it’s the status quo. They haven’t necessarily found an impetus to start with alternative options. I’m definitely sending my results back to the managers of the ranches that I worked on and would like to publish somewhere where the information will reach the right people.
Will your experiences influence your direction after Princeton? My experience doing research in Kenya definitely influenced what I want to do after graduation. My experience made it clear that field research is something I really enjoy, and I am hoping to take a couple years off and then pursue a vet degree and PhD so that I can do disease ecology research. In my time off, I’m hoping to gain more research experience either back in Kenya or in the United States.