Seeking Stability: How soft-release can improve outcomes for captive turtles released into fragmented environments
By Tyjaha Steele
For species rescued from captivity from illegal pet trade or wildlife trafficking, reintroduction into the wild goes beyond relocation. It requires reestablishing behaviors and instincts necessary for survival in nature. Animals with diminished natural instincts often struggle to adapt to unfamiliar environments. This leaves them vulnerable to threats like human activity and reduces their chances of thriving in their natural habitat.
Recognizing this challenge, researchers at the University of Georgia’s Savannah River Ecology Laboratory worked to boost the survival rates of 26 long-term captive Eastern Box Turtles (Terrapene carolina carolina) by releasing them to the Savannah River Site in Aiken, South Carolina, using a method called soft-release.
“Soft-release is frequently used in wildlife reintroductions and involves gradually acclimating animals to their release site before allowing them to roam freely,” states Tracey Tuberville, senior research scientist at SREL and lead scientist for this study.
Of the 26 turtles reintroduced, 16 were soft-released and slowly introduced to their new environment, while 10 were hard-released and placed directly into their new habitat. An additional 10 resident turtles served as a control group for comparison. A key metric of success that was tracked throughout the study was settling time.
“Settling time is the amount of time that was required for an animal to establish their home range and was an important metric used to determine whether soft-release was effective,” explains Ryan Rimple, a recently graduated UGA SREL master’s student and now PhD student at New Mexico State University, who was a lead contributor on this paper.
Soft-released turtles showed first-year survival rates of 87.5%, closely following those of their resident counterparts, and their chances of survival are likely to improve in subsequent years, as they continue to become acclimated to their new habitat. They settled into their new environment 21 days earlier than hard-released turtles, stayed closer to their release site, and showed reduced wandering after acclimation. By reducing these risky behaviors, soft-release is
likely to help promote high survivorship in turtles following release.
Tuberville asserts, “A key component of acclimation is confining turtles to a temporary enclosure at the release site to help curb their initial flight response that might occur when placed in an unfamiliar environment.” This helps to ease the stress of relocation. Temporary penning allows turtles to adjust to their surroundings, giving them the opportunity to locate necessary resources. The soft-release method is ideal for smaller or fragmented habitats, where limiting movement reduces the risks of road crossings, urban development, and exposure to predators.
The behavior and survival rates of hard-released turtles followed a different pattern throughout the study. They displayed slightly higher first-year survival rates, ranging from 90% to 100%, but established home ranges farther from the release site due to greater exploratory movements. Research indicates that this increased movement could be harmful in fragmented release sites, where animals may face higher mortality rates during the exploratory phase. “Being active on the surface is riskier to turtles than being hidden under leaf litter or other shelter sites. Obviously, turtles need to move to find food and mates. The more active they are on the surface, the greater the risk of encountering potential hazards such as roads or predators.” Tuberville explains.
Despite higher initial survival rates, the increased movement of hard-released turtles and associated risks highlight the need for a stabilized long-term approach. The findings from this study suggest that soft-release offers such stability for animals reintroduced after challenges like illegal trade or habitat loss.
Reflecting on the broader impact, Rimple adds, “the reduction we observed in the post-release exploratory phase is important as most studies have shown that this phase of post-release behavior is when turtles are most vulnerable to mortality. By reducing the risk of wandering, soft-release can increase survival rates, allowing released turtles the opportunity to add to their new population over time.”
The original study titled, “Translocation of Long-Term Captive Eastern Box Turtles and the Efficacy of Soft-Release: Implications for Turtle Confiscations,” was published in the Northeastern Naturalist and was written by Ryan Rimple, Michel Kohl, Kurt Buhlmann, and Tracey Tuberville.