Wolves without borders: Transboundary survival of wolves in Banff National Park over three decades

Abstract

Large carnivores are important ecological drivers of ecosystem dynamics when they occur at ecologically effective densities. They are also challenging to conserve, especially in transboundary settings such as along borders of parks and protected areas. Here, we tested for effects of transboundary movements on survival of 72 radiocollared gray wolves from 1987 to 2018 in and adjacent to Banff National Park, Canada. We fit Bayesian counting-process survival models to known-fate radiotelemetry data and tested for the influence of intrinsic covariates such as sex and age, time, and movements outside of protected areas on survival of wolves. We also estimated cause-specific mortality. Non-parametric survival was 0.733 (95% CI 0.622–0.816), and the top Bayesian survival model indicated that wolves outside the park had much lower annual survival rates (0.44, 95% BCI = 0.24–0.65) compared to wolves inside the park (0.84, 95% BCI = 0.73–0.91). The cumulative risk of mortality was on average 6.7 times higher (odds ratio 95% BCI = 2.2–21.4) for wolves outside the park, peaking during the winter hunting and trapping seasons. We found weak evidence for declining survival over time, opposite to patterns predicted by density-dependence. Bayesian cause-specific mortality indicated that the top three sources of mortality were trapping (rate = 0.080, 36% of mortality), followed by hunting (0.053, 18%), and highway (0.046, 18%) mortality. Surprisingly, we found no intraspecific mortality, and low dispersal from Banff National Park. This demographic profile is akin to other exploited populations across North America. While we were unable to combine survival rates with reproduction to estimate population trends, the overall mortality rates within our study area are consistent with a stable wolf population. Nonetheless, the long-term stability and ecological effectiveness of wolves likely differed inside and outside of protected areas, which highlights a challenge with managing transboundary carnivores exposed to different management regimes.