Estimating density of native carnivores in central Chile landscapes using a simulated movement model, cameratrapR: insights on their potential exotic prey dietary subsidy.

BACKGROUND

Species-specific density is an essential parameter for evaluating population stability and ecosystem health. We estimate the population density of native carnivores, South American gray and culpeo foxes ( spp.), guiña () and Andes skunk (), in central Chile, inferring on the potential influence of the availability of introduced exotic prey on their population dynamics.

METHODS

Monitoring with camera traps was conducted from March 1, 2021, to March 31, 2022, across three distinct landscapes representative of the coastal mountain range of central Chile: Mediterranean coastal thorn forest, Mediterranean coastal sclerophyllous forest, and exotic monoculture tree plantations. We estimated density using an R package, cameratrapR, where animal movement was simulated using a correlated random walk within the camera grids. Simulations were run for a range of numbers of individuals, representing a gradient of population densities. We matched these results and the observed photo records using a machine learning algorithm, random forest, thereby estimating population density and its 95% confidence intervals.

RESULTS

A total of 10,046 trap days resulted in 9,120 photographs of carnivores, with 3,888 independent records. Our findings indicate that spp. are the carnivore species with the highest population density in central Chile (4.1-4.8 individuals/km). Furthermore, their density was higher in the exotic monoculture tree plantation ecotype compared to native forests, suggesting a dietary subsidy from non-native prey. We report the first population density estimates for (1.8-2.2 individuals/km) and (0.7-1.3 individuals/km) in the three landscapes, showing different habitat preferences and resource availabilities across landscapes. The results highlight the complex interactions between carnivores and their environments, particularly the role of exotic introduced species as prey items in shaping native carnivore populations. These findings also provide insights into carnivore adaptability and the implications for biodiversity conservation.