QGIS mapping for sea turtles tracked by satellite telemetry
ISAAC DEJESUS
Abstract
Many animals naturally travel long distances throughout their lifetimes and face different challenges while doing so. In an oceanic environment, it can be difficult to track animals once they move away from coastlines. With the discovery and implementation of satellite tagging, tracking movements has become much easier. The data that is provided by tags is complicated to plot on a map, however there are different software programs that aim to make this possible. This study examined the use of the open-source software program QGIS (www.qgis.org) to map satellite-retrieved positional data from cold stunned sea turtles that had stranded on New York beaches and were rescued, rehabilitated, tagged and released. The data and information provided by the created maps can assist researchers in answering ecological questions about these endangered species, and how they respond to rehabilitation efforts. To create the map, the satellite tag data file had to be imported into QGIS. Positional data provided in a CSV format was directly imported into QGIS through the delimited text layers tab with the proper axis values present on a map of New York. Resulting maps can be modified to emphasize the migratory movements over specific time periods. This project illustrates that QGIS is a powerful mapping software that can provide positional data over time for migratory species that travel significant distances under water and can help clarify ecological hypotheses related to habitat use and migration patterns in cold stunned sea turtles. Furthermore, this project supports broader ecological initiatives and conservation efforts for these endangered species Atlantic sea turtles.
Introduction
• Sea turtles are influenced by numerous anthropogenic factors such as vessel strikes, fishery interactions, hunting, pollution, habitat degradation, beach development, and egg harvesting (Innis et al., 2019).
• Understanding movement patterns and the factors that affect animal distribution are integral components of behavioral ecology, conservation and protected area management (Schofield., et al., 2007).
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• Satellite telemetry to track sea turtles following rehabilitation from injury provides necessary knowledge of migratory patterns, behavioral changes, and life expectancy in turtles that have been released (Cejudo et al., 2019).
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• Post-release tracking of rehabilitated sea turtles is a valid means to monitor the success of the rehabilitation process, while obtaining additional information on natural migratory movements and behavior (Robinson et al., 2020).
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• QGIS (qgis.org) is a free mapping software that allows researchers to map positional data obtained via satellite telemetry studies and address ecological hypotheses about animal movements.
Study Objective
• To use an open-source software program, QGIS, to map satellite-retrieved positional data from cold stunned sea turtles that had stranded on New York beaches and were rescued, rehabilitated, tagged and released.
• This technology will allow researchers to understand migratory patterns and potential anthropogenic threats that freshly rehabilitated turtles may face after they are released back into the wild.
MATERIALS & METHODS
Downloading QGIS:
• In order to create a digital map, QGIS software needed to be downloaded
• The link to download QGIS for both windows and mac: https://qgis.org/en/site/
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Data Files:
• The data files used were positional data, 30 days post-release for 3 turtles.
• A zip file was first extracted into two separate text files that contained the same data.
• The files were then added through the delimited text layer in QGIS in a CSV format for the positions to load.
Map Creation:
• Create a new empty project in the QGIS opening screen.
• On the left side of QGIS, head to browser, then XYZ Tiles and select Open Street Map
• Now with the blank map template, zoom in to New York, and add the data points.
• Head to the layer tab, then add layer, and open delimited text layer.
• Once in the delimited text layer, add the csv file as a UTF-8, leave the file in a CSV format, adjust the x field to longitude and the y field to latitude and add to create the map.
Results
• Fig. 4a,b shows turtle 1 tracked from August 5, 2018 to August 25, 2018.
• Turtle 1 traveled west to east where it made occasional stops in one area where feeding or breeding grounds could be located based off the positional behavior.
• Fig. 5a,b shows turtle 2 tracked from August 23, 2019 to September 9, 2019.
• Turtle 2 traveled in two directions being east and south.
• Spent most of time inshore feeding and roaming
• Fig. 6a,b shows turtle 3 tracked from August 9, 2019 to August 29, 2019
• Turtle 3 traveled in the north to south directions.
• Spent most of time inshore feeding and roaming as turtle 2
Discussion/Conclusion
• QGIS is an effective program to create maps that illustrate migration patterns of turtles from satellite telemetry data.
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• The positional data from turtle 2 and 3 appear similar as they both traveled around the same areas, likely feeding grounds.
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• Data maps made with QGIS software could be used further in the protection efforts in turtle conservation; to understand where turtles are utilizing New York’s habitats.
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• This project will continue to support broader ecological initiatives and conservation efforts for endangered Atlantic sea turtles.
Challenges and Future Directions
• Learning how to use QGIS took some time but was relatively user friendly.
• A challenge faced from a software perspective was converting the data into a CSV file as the file was in a txt format.
• It may be helpful to have more data points for each turtle.
• Future directions should investigate species-specific and age-class specific migration patterns following rehabilitation and release.
Literature Cited
Cejudo, D., Varo-Cruz, N., Liria, A., Castillo, J. J., Bellido, J. J., & Lopez-Jurado, L. F. 2006. Transatlantic Migration of Juvenile Loggerhead Turtles (Caretta caretta L.) from the Strait of Gibraltar. Marine Turtle Newsletter. 114: 9-11
Schofield, G. C. M. Bishop, G. MacLean, P. Brown, M. Baker, K. A. Katselidis, P. Dimopoulos, J. D. Pantis, G. C. Hays. 2007. Novel GPS tracking of sea turtles as a tool for conservation management, Journal of Experimental Marine Biology and Ecology, Volume 347, Issues 1– 2: 58-68.
Innis, Charles & Finn, Sarah & Kennedy, Adam & Burgess, Elizabeth & Norton, Terry & Manire, Charles & Harms, Craig. (2019). A Summary of Sea Turtles Released from Rescue and Rehabilitation Programs in the United States, with Observations on Re-Encounters. Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal. 18. 3-9. 10.2744/ccb-1335.1.
Robinson NJ, Deguzman K, Bonacci-Sullivan L, DiGiovanni Jr. RA, Pinou T. 2020. Rehabilitated sea turtles tend to resume typical migratory behaviors: satellite tracking juvenile loggerhead, green, and Kemp’s ridley turtles in the northeastern USA. Endangered Species Research. 43:133-43.
Acknowledgements
Thanks to Dr. McFarlane for her insight and feedback on this project and poster, to the New York Marine Rescue Center in Riverhead, NY for the positional data sets used to create the maps, and to Manhattanville College’s Division of Natural Sciences, Mathematics & Computing for the resources needed to complete this preliminary study.
Isaac Dejesus '21
My name Isaac Dejesus and I am a senior at Manhattanville College. During the Fall of 2020 and this spring semester I did research on QGIS mapping in sea turtles that were tracked by satellite telemetry.