Feral swine harming insular sea turtle reproduction: The origin, impacts, behavior and elimination of an invasive species

Abstract

Feral swine are among the world's most destructive invasive species wherever they are found, with translocations figuring prominently in their range expansions. In contrast, sea turtles are beloved species that are listed as threatened or endangered throughout the world and are the focus of intense conservation efforts. Nest predation by feral swine severely harms sea turtle reproduction in many locations around the world. Here we quantify and economically assess feral swine nest predation at North Island, South Carolina, an important loggerhead sea turtle nesting beach. Feral swine depredation of North Island sea turtle nests was first detected in 2005, with annual nest monitoring initiated in 2010 documenting nearly total losses to feral swine in 2010 and 2011. The cumulative valuation of annual losses for North Island from 2010 to 2016 ranged as high as $1,166,500. To improve nesting success, an integrated approach for eliminating feral swine was implemented in 2010 and greatly intensified in 2013 by adding federal experts. Removal efforts were challenging due to the island's remoteness and impenetrable habitats, weather, hazards in accessing the island, and wariness of the animals, especially as their population diminished. Removal of the final 11 swine required efforts from 2014 to 2016. Nest predation was highly variable and provided another example of the significance of conditioning by feral swine to sea turtle nests on the consequent severity of nest predation. Even the final individual inflicted heavy losses before his removal. Genetic analyses of feral swine removed from North Island and the adjacent mainland revealed that the island's population did not originate from the nearby mainland, meaning they were (illegally) introduced to the island.

Long-term changes in body size of green turtles nesting on Trindade Island, Brazil: Signs of recovery?

“…turtles in Western Cape York Peninsula, Australia (Whytlaw et al, 2013). Moreover, and consistent with our theory about the benefits of pig eradication on Trindade to local green turtles, pig removal at Keewaydin Island (Florida, USA) resulted in a decrease from 41.6% to 27.7% in green turtle/loggerhead nest loss in just two years, and to 9.4% after four years (Engeman et al, 2014(Engeman et al, , 2019. Such positive signs after the eradication of rats on other nesting beaches suggests that the removal of rats on Trindade had a profound positive influence on the local green turtle population.…”

DNA metabarcoding reveals consumption of diverse community of amphibians by invasive wild pigs (Sus scrofa) in the southeastern United States

“…While other studies in the U.S. have seen higher occurrences of small mammals in wild pig diets with over one third of samples containing small mammals 14 , 23 , the short-tailed shrew ( Blarina brevicauda ) was the only small mammal detected in our study and occurred in only one sample. These findings suggest that in South Carolina, amphibians appear to be among the more vulnerable wild pig prey groups in contrast to other vertebrate taxa that have been documented in the diet at higher levels elsewhere 14 , 35 , 61 . However, given the dominance of plants, more in-depth studies focused within periods of peak vulnerability of ground nesting birds or other concerned taxa (e.g., nesting seasons) are needed to fully capture the potential extent of impacts of wild pig predation.…”

Predation of sea turtle eggs by rats and crabs

“…For example, introduced feral pigs historically decimated green turtle nests on Trindade Island, Brazil and pig removal has led to recovery of nesting numbers (Pereira et al 2023). Similarly, on Keewaydin Island, Florida, pig eradication resulted in a decrease from 87% to just 1% of nests destroyed by this invasive predator (Engeman et al 2019). In some cases, eradication of invasive species may have very broad ecosystem benefits.…”