WEC Seminars: Daniel Evans

This is a summary of a talk given by Daniel Evans on Monday, March 19th, 2018.

The Path Most Traveled: Using Satellite Telemetry to Identify and Characterize Migration Pathways and Foraging Areas of Four Species of Marine Turtle in the North Atlantic and Wider Caribbean

By Yichao Zeng

Sea turtles are iconic marine reptiles that are both loved and threatened by humans. Daniel Evans, a PhD student at the University of Florida, has over 12 years of experience working with the Sea Turtle Conservancy (STC). His talk is based on his dissertation using satellite telemetry to track four sea turtle species. The satellite telemetry was conducted as part of STC’s online sea turtle tracking educational program. At the University of Florida, Daniel is advised by Dr. Ray Carthy.

Daniel Evans started by talking about background knowledge which is crucial to understand his work. The use of satellite telemetry was primarily for large mammals in the Early 70s. In the Late 70s, this powerful tool was used for the loggerhead sea turtle for the first time. The location accuracy depends on how long the satellite passed over the transmitter and number of messages from the transmitter.

He then explained why wildlife ecologists track sea turtles. Tracking sea turtles can provide a wide range of knowledge about these animals, including their complex life history, migration, and threats (e.g. bycatch, pollution, harvest, loss of habitat). Three different types of general movement are observed in sea turtles: long distance, short distance, and restricted). The factors that drive sea turtle movement including the patchiness of resources and interaction among oceanic features. An important mission in the conservation of sea turtles is to preserve their natural habitat. Marine Protected Areas (MPAs) have been established to meet this conservation need.

The primary objective of his project is to model movement patterns of the sea turtles. The results indicate that most turtles use the entire Atlantic. A random walk model was applied to the movement data. Kernel density analyses were also conducted to identify key foraging areas. An interesting finding is that sea turtles in the Gulf of Mexico tend to search within foraging areas, while animals in the North Atlantic Ocean tend to search between foraging areas. Loggerheads have larger foraging areas than Green and Hawksbills. Each species uses MPAs in different ways.