Mortality causes and annual survival rates of red foxes (Vulpes vulpes).
Mortality causes and survival rate estimates from individual follow-ups of GPS-collared animals provide reliable demographic data, but such estimates are rare for red foxes Vulpes vulpes. We used data from 126 GPS-collared red foxes tracked between 2011 and 2019 across a latitudinal gradient in central Sweden and Norway to quantify mortality causes and estimate annual survival probabilities using the Andersen-Gill extension of the Cox proportional hazards model. Hunting was the dominant mortality cause (63%), followed by vehicle collisions (14%), stress or malnutrition (11%), sarcoptic mange (9%), and predation (3%). Annual survival was 0.58 for adults and 0.32 for subadults. Subadults had approximately twice the hazard of adults, males had elevated hazard relative to females, and mortality risk was highest in autumn and early winter. These collar-based estimates are strikingly similar to mark-recovery estimates from the same region nearly five decades earlier, despite an intervening population collapse from sarcoptic mange, subsequent full recovery, and a major decline in harvest pressure. This convergence is consistent with density-dependent regulation at a food-determined and food-limited carrying capacity, suggesting that current harvest levels are not limiting the population. Furthermore, human-caused mortality was approximately four times greater than natural mortality, illustrating that living in close proximity to humans -- which often favours generalist predators such as red foxes -- may also come at a cost of increased mortality risk. Developing validated census methods for red foxes in boreal Scandinavia is identified as a key priority for quantitative population management.