Unleashing the unknown: feral dog ecology and wildlife interactions in the southernmost island ecosystem

Domestic dogs ( Canis lupus familiaris ) are the most widespread carnivores and act as disruptive agents in insular ecosystems. In Tierra del Fuego, feral dogs have expanded into rural landscapes, affecting wildlife and livestock. Using 21 camera traps, we assessed their presence, activity, and interactions with the Fuegian culpeo fox ( Lycalopex culpaeus lycoides ), the chilla fox ( Lycalopex gymnocercus ), and guanacos ( Lama guanicoe ). We identified 117 individuals, roaming solitary or in groups of up to nine. Reproductive activity was evident, with 87 pup detections, especially during autumn and winter. Dogs exhibited stable bimodal diel patterns, peaking in the morning and late afternoon, and shifting toward nocturnality in winter. Overlap was moderate-to-high with guanacos (Δ = 0.73, peaking in winter at Δ = 0.82) and moderate with chilla foxes (Δ = 0.65). The endangered culpeo was never recorded, raising conservation concerns. Chase events and injured guanacos evidenced direct predatory impacts. Over five years, dog detections increased almost 230%, while chilla detections declined by 66%, suggesting competitive displacement. Forest patches were frequently used by dogs, potentially as shelter and breeding sites. These findings suggest that feral dogs function as apex predators in this system, highlighting the urgent need for management to mitigate their ecological and economic impacts.