Giant otter populations persist and demonstrate recovery potential in suboptimal freshwater ecosystems degraded by gold mining

• Mining negatively impacts giant otter occurrence and abundance via water quality. • Water transparency and oxygen levels drive giant otter distribution and abundance. • Protected areas ensure stable giant otter populations; occurrence varies seasonally. • Otters can adapt to disturbed habitats, with potential to recolonize mined areas. In both terrestrial and aquatic ecosystems, land conversion is driving the depletion of biodiversity. Freshwater systems are especially vulnerable due to their accessibility and sensitivity to human pressures. Freshwater megafauna, which depend on suitable environmental conditions and stable prey resources, can serve as indicators of ecosystem health. We carried out visual surveys in four neotropical protected areas and the Madre de Dios gold mining corridor to examine how human pressures, particularly artisanal gold mining, influence the distribution and space use of giant otter populations. In unprotected lakes, extractive activities negatively impacted giant otter occurrence and group size, primarily through reduced water quality. Otter distribution and abundance were positively associated with water quality parameters, specifically transparency and dissolved oxygen. Protected areas maintained more stable otter populations, and otter occurrence showed seasonal variation, increasing during dry seasons. Within unprotected lakes, otters showed a tendency to occur in areas near sites with recent evidence of mining, a finding that suggests potential behavioral tolerance to lower-intensity disturbances and ability to recolonize disturbed freshwater habitats, rather than the predicted avoidance of such areas. However, this interpretation requires further investigation into long-term demographic impacts and the influence of unmeasured cumulative human pressures. Our multi-scale dataset provides unique evidence on the impacts of extractive activities on giant otter populations, underlining the need for multi-pronged conservation strategies. Our findings also emphasize the importance of protected areas in preserving neotropical freshwater biodiversity while highlighting the need to extend conservation efforts beyond current boundaries. Further research is needed on the impacts of extractive activities on otter demography and, critically, to test the hypothesis regarding the potential role of abandoned mining ponds as novel habitats for restoration of megafauna species and freshwater communities.