CSE Prof. Ryan Kastner did not participate in the international expedition that sent fellow UC San Diego researchers to the Cayman Islands in connection with the Engineers for Exploration (E4E) program, which enlists students to build technologies to help scientists, conservationists and explorers. Kastner co-directs the program with the Qualcomm Institute's Albert Lin and Curt Schurgers, and he contributed to the Cayman Islands in formulating the research plan to test the use of airborne drones to track and monitor the nesting movements of critically-endangered iguanas. At 30 to 40 inches long, the Sister Islands Rock Iguana (or Lesser Caymans Iguana) is one of the world’s largest species of iguana. Although the lizards are indigenous to Cayman Brac and Little Cayman (together called 'sisters' because of their similar shape and size), predation from introduced mammals, road mortalities and habitat loss from human development have eliminated all but 1,500 iguanas from the islands, putting the animals on the endangered list.
E4E's co-director Schurgers and electrical and computer engineering senior Nathan Hui traveled to the Cayman Islands as part of a joint research expedition involving the San Diego Zoo Institute for Conservation Research, Mississippi State University, and the Cayman Islands Department of Environment. The goal was to determine whether drones could be useful even over Cayman terrain. "The iguanas are difficult to track on foot," said Hui, who worked on the drone system. "Most of the island is mangrove swamps. Just one kilometer takes around four hours to walk." The expedition flew only one drone at a time, and it only required human control during takeoff and landing. Once at cruising altitude of 30 meters, it fles in a lawnmower pattern, searching for radio transmitters previously attached to each iguana's tail. The drone's search radius is approximately 30 meters, which Kastner describes as "just barely enough to pick up the signal, otherwise you have to fly lower, which means there's more risk with any topography change."
The Cayman project is the second drone deployment in the region, after a test in the Dominican Republic in 2015 that fell short of expectations because the drone receiver built by E4E students in San Diego was not strong enough. As a result the students learned to use radio transmitters that emit stronger signals. They also simplified operation of the drones, and the next step will be to improve the range at which drones can detect more powerful signals. "The technology can be easily adapted to fit another transmitting device," said Kastner, "including animals that use larger collars".
Iguanas are relatively small, and the size of a transmitter limits the strength of a signal; if the drone were used to track lions in Africa, for instance, it could track them more widely since the transmitter on a lion could be bigger to send out a much stronger beacon.
Read the complete Qualcomm Institute news article on the Caymans project.