Ringed Seal (Pusa hispida) Haul-Out Behavior and Emergence Timing in the Bering, Chukchi, and Beaufort Seas

Ringed seals are ice-associated marine mammals that excavate lairs in snowdrifts on sea ice during winter for resting and pupping. Before lairs melt in the spring, seals shift from predominantly hauling out in lairs to predominantly hauling out on the surface of the ice to bask and molt, a transition we refer to as "emergence." Emergence timing is poorly understood, which hinders planning and interpretation of aerial surveys for population monitoring. We used hidden Markov models (HMMs) to analyze haul-out timelines from satellite-linked transmitters to estimate emergence dates of ringed seals from 2005 to 2021 in the Bering, Chukchi, and Beaufort seas. Our HMMs were fit separately for adults and subadults and included a lair state and an emerged state, characterized by differences in diel behavior and the daily proportion of time seals spent hauled out. We explored covariates of the transition probability between states, including day of year, daylength, sea-ice concentration, air temperature, and indices of snow melt progression. Emergence probability for adults was associated with longer daylengths and warmer temperatures. Median emergence date was 12 May (within 3 days of previous estimates from aerial surveys) and emergence date was positively associated with latitude. Subadults showed weaker seasonal changes in haul-out behavior, potentially making HMMs more suitable for adults than subadults. Our results contribute to our understanding of ringed seal behavioral ecology, provide useful information for aerial surveys, and demonstrate the value of haul-out data from tagged ringed seals for monitoring emergence timing in a warming Arctic.