Long-term wild recovery and resilience of green turtles Chelonia mydas to various anthropogenic injuries

Injuries from human activities are commonly reported in marine turtles worldwide, and efforts to promote recovery through treatment at rehabilitation centers have proven important. However, little is known about the resilience of turtles recovering in the wild without human intervention. Here, we document the natural healing of external injuries in green turtles Chelonia mydas using repeated in-water photographic sightings from a coastal foraging ground at Liuqiu Island, Taiwan. Drawing from 2 photo-identification databases spanning 14 yr, we identified 105 injured turtles among 7233 sightings (709 individuals). Thirteen turtles with 19 injuries had multiple re-encounters, allowing for estimation of healing durations. Average healing times were for propeller strikes: 527 d; fishing line entanglements: 538.5 d; and for injuries of unknown causes: 560.2 d, with severe injuries taking 600 d and minor injuries 491 d to recover. Recovery trajectories in wild green turtles were slower than those reported for other marine megafauna. Long-term resightings of 5 individuals confirmed survival after recovery from severe injuries; these turtles remained detectable for an additional 106 to 2264 d, after which monitoring was discontinued. Approximately 10.5% of injured turtles suffered recurring injuries from propeller strikes, emphasizing the need for targeted conservation measures, including go-slow zones, recreational fishing regulations, and public outreach. This study provides the most extensive evidence of natural injury recovery in marine turtles to date, demonstrating the long recovery durations and impacts of multiple recurring injuries. This research highlights the value of long-term monitoring, supported by citizen scientists, in assessing sublethal impacts and guiding mitigation for marine megafauna.