Ecological feasibility of reintroducing small wild cats (Leopardus guttulus and L. wiedii) on Santa Catarina Island, southern Brazil

The dispersal capacity of small wild cats is essential for maintaining functional populations in fragmented landscapes. However, when local extinctions occur, particularly in insular systems surrounded by densely populated continental regions, the loss of mesopredators can trigger complex ecological cascades that restructure communities and favor generalist or invasive species. Santa Catarina Island, in southern Brazil, represents one such case in which the disappearance of small wild cats has coincided with the dominance of opportunistic native species and the expansion of domestic and exotic fauna, including the invasive black-tufted marmoset (Callithrix penicillata). To evaluate the ecological feasibility of reintroducing small wild cats, this study integrated habitat suitability analysis, potential prey population size and biomass estimation, and camera trap monitoring within the Meiembipe Municipal Wildlife Refuge (REVIS Meiembipe), a municipal protected area on the Island. Secondary data from Projeto Fauna Floripa (2019–2021), based on island-wide camera-trap surveys, and complementary field records collected between 2024 and 2025, were combined to assess environmental suitability and identify potential release sites. Camera-trap data indicated low domestic-animal presence (<20% of sampling sites) and high potential prey biomass (>167,000 kg), based on capture–mark–recapture studies and literature-based density estimates. Expert consultations (n = 11) suggested the feasibility of reintroducing Leopardus guttulus and L. wiedii. Recommendations included pre-release rehabilitation; phased soft releases of individuals meeting genetic, behavioral, and health criteria; continuous monitoring of species composition—particularly the current dominant species—and consideration of historical records confirming the former presence of both felids on the island; and telemetry-based post-release monitoring. These findings suggest the ecological viability of Santa Catarina Island for reintroduction and highlight the region’s role in safeguarding small felid populations in the Atlantic Forest, emphasizing the island’s unique capacity as a genetic refuge for L. guttulus, which is threatened on the mainland by hybridization with L. geoffroyi.