Sea ice influence on male polar bear survival in Hudson Bay

Abstract

Environmental variability and seasonality of resources influence species distribution and demographic parameters such as survival. We quantified the spatiotemporal dynamics of sea ice that remains in Hudson Bay during break-up (remnant ice) and assessed relationships with apparent survival for three age classes of male polar bears (Ursus maritimus Phipps, 1774): subadult (1–4 years), prime age (5–19 years), and senescent (≥20 years) captured in Western Hudson Bay in 1980–2019. Remnant ice distribution varied annually, and we identified ice-related covariates that were correlated with detection probabilities and male apparent survival. Apparent survival declined by 10% for prime age males during the earliest retreat dates within Hudson Bay. Apparent survival for senescent bears declined during earlier sea ice retreat within western Hudson Bay. Subadult apparent survival was time constant and not significantly influenced by sea ice; however, detection probability was higher when remnant ice occurred in the west compared to the eastern half of Hudson Bay. Our results suggest that spatiotemporal sea dynamics at varying spatial scales affected males based on age class, had important impacts on estimating apparent survival, and has implications for assessing population status.

Keywords

• sea ice
• polar bears
• transients
• survival
• climate change