Design suitable and you may diagnostics
We fit our Bayesian state-space model, consisting of both movement and observation process components, using Markov chain Monte Carlo (MCMC) methods. We assigned uninformative priors whenever there were no a priori expectations about the relationships of the model parameters and the movement behavior states (see Appendix S1). letter,t) within each iteration of the MCMC algorithm (see Appendix S2). We initialized six chains from random starting values drawn from the prior distributions. After initial pilot tuning and burn-in, we ran the chains until the univariate Gelman–Rubin potential scale reduction factor (PSRF) for monitored parameters was <1.2 and effective sample sizes exceeded 4000. This required about 6 million iterations per chain, where 1 million iterations for each parallel chain required about 100 h using six cores of a 3.7-GHz processor. Data and code can be found in Data S1.
Overall performance
Considering rear modes to possess condition projects, i discovered these bearded seals spent 70% of its implementation attacks regarding benthic foraging county (B). They hauled out on ice (county We) and rested on ocean (condition S) in roughly equal size, however, there can be a clear regular part into the interest finances one of the fresh new hauled out on freeze (I), benthic foraging (B), and you can transportation (T) says that coincided for the summer refuge and you may winter progress out-of ocean ice in the Cold (Desk dos). The seals presented intensive benthic foraging across the continental shelves of the Chukchi otherwise Beaufort waters due to the fact sea frost receded northward inside summer time. We discovered little evidence of such ice-associated seals pulling out on house, regardless if near the coastline in largely ice-free months in the summertime. Interestingly, a grownup men temporarily went northern of the Beaufort coastal shelf from inside the late and you may try predicted for hauled on the fresh falling out in clumps sea freeze line ranging from bouts out-of middle-h2o foraging throughout the better oceans of your Canada Basin (Fig. 2). You can expect a detailed cartoon away from forecast movements and you may county projects for everyone seals prior to bathymetry and you may ocean freeze safety when you look at the Appendix S3.
- There had been seasonal differences in pastime finances between “summer” (of tagging in late June and you may very early July so you can 29 Sep), “autumn” (step one October so you’re able to 29 December), and you may “winter” (step 1 January up to tag losings between March and you will April) you to definitely coincided towards the southern improve away from cold weather sea ice inside the new Arctic. Pastime budget descriptions was basically calculated based on the rear mode away from time invested within the each condition that have lower (LCI) and you may top (UCI) credible menstruation predicated on 95% highest posterior density. Private close interest finances are part of Appendix S4.
As expected, the resting states (I, S, and L) exhibited shorter step lengths, no directional persistence, and lower proportions of each time step diving >4 m below the surface based on state-specific parameter estimates (Fig. 3; see Appendix S4 for posterior sumeters). Both the mid-water foraging (M) and transit (T) states exhibited longer step lengths, lower proportions of dry time, and higher proportions of diving >4 m below the surface. Only the transit state exhibited strong directional persistence, but state M exhibited moderate directional persistence for some individuals (Fig. 3). The benthic foraging (B) state generally exhibited moderate step lengths, no directional persistence, lower proportions of dry time, higher proportions of diving >4 m below the surface, and considerably higher benthic dive counts (posterior median for ?B = 41.4; 95% highest posterior density interval: 41.2–41.7). The resting (?I = ?S = ?L = 9.7; 95% HPDI: 9.4–10.0) and transit (?T = 15.0; 95% HPDI: 14.5–15.5) states exhibited moderate benthic dive counts, while the mid-water foraging state generally had the lowest benthic dive counts (?M = 1.5; 95% HPDI: 1.3–1.7; Fig. 3). The moderate benthic dive counts for the resting and transit states could be attributable to mid-interval state switches, but there certainly could have been opportunistic benthic foraging during transit. There also could have been high-speed, directionally persistent benthic dives while transiting in relatively shallow shelf waters.