Listening for turtles
Sea turtles are beautiful, graceful and inspiring, but their migratory and mysterious nature makes conservation challenging.To address this, four of South Africa’s aquariums and a research institute are acoustically tagging rescued and rehabilitated sub-adult and adult turtles. Bayworld, a museum in Gqeberha with a long-standing turtle rescue programme, leads the project with support from Cape Town’s Two Oceans Aquarium Foundation, Durban’s SAAMBR, the East London Aquarium, and the national Acoustic Tracking Array Platform (ATAP).
Acoustic tagging may seem unusual for turtles, but the technology involves attaching small, matchbox-sized tags to their shells. These tags emit pings picked up by 285 moored receivers in South African waters, providing researchers with data when the receivers are retrieved and downloaded.
Talitha Noble-Trull of the Two Oceans Aquarium Foundation likens the process to receiving voice notes from a loved one travelling. The project, now in its sixth year at Bayworld, began in 2020 amid the pandemic. With over 30 tagged turtles, the goal is to understand their movement patterns along South Africa’s coastline and assess post-rehabilitation success.
Resource-intensive
Rehabilitating turtles – whether hatchlings, sub-adults, or adults – is resource-intensive, requiring months or even years of care. The project aims to determine whether conservation efforts are making a difference. Since turtles have long lifespans, their tags, which last up to 10 years, can provide valuable insights into their migration and habitat preferences.
In December, the Two Oceans Aquarium Foundation released four sub-adult turtles into De Hoop Marine Protected Area (MPA), a rich habitat with ample resources.
Initial data from previously tagged turtles show promising results. Some remained in De Hoop for months, while others travelled along the coast before returning. The receivers in De Hoop will soon be retrieved, potentially offering more insights into the turtles released in December. This long-term data collection helps researchers understand turtle retention along the coastline, the significance of inshore zones, and the role of MPAs in their survival.
Costly exercise
ATAP continues to expand, with projects extending listening coverage to Mozambique, Tanzania, Madagascar, Seychelles, Réunion and potentially the Comoros.
Beyond turtles, researchers use acoustic tagging for fish, sharks, skates and rays. The technology is costly – a basic tag costs about N$8 500, while receivers operate at depths of 15 to over 100 meters, requiring specialised retrieval methods.
Data collected through acoustic tagging answers key ecological questions, such as whether turtles stay in certain areas, migrate seasonally, or respond to water temperature changes. It also helps identify turtle hotspots, like De Hoop and Sodwana’s coral reefs, where turtles exhibit social behaviour. These insights inform conservation efforts and marine management strategies.
Acoustic tagging has already influenced policy changes, such as seasonal protections for giant kingfish in Maputo National Park. While long-term conclusions on South Africa’s tagged turtles are still forthcoming, the initial data is encouraging. More funding, technological advancements, and increased tagging will enhance understanding and protection of these endangered ocean ambassadors.