Linking northern fur seal dive behavior to environmental variables in the eastern Bering Sea

Abstract

Abstract. Northern fur seals (Callorhinus ursinus) breeding on the Pribilof Islands, Alaska have declined dramatically over the past 40 years. Effective conservation of northern fur seals depends on understanding the foraging behavior of adult females whose foraging success is linked to pup survival. We determined the foraging behavior for 11 tagged lactating female northern fur seals from the Pribilof Islands using a statespace modeling approach with an autoregressive movement model. To interpret at-sea behavior in the context of oceanic habitat, we spatially and temporally matched high-resolution reconstructed tracks to a set of environmental covariates that included: commercial groundfish catch, sea surface temperature, primary productivity, wind speed, depth and time of day. We used a Bayesian hierarchical framework to implement a multinomial regression model to link behavior to environmental covariates and account for the mismatch of scale between fur seal behavior and the environmental variables by incorporating an errorin-covariates approach into the hierarchical model. The Bayesian framework allowed us to build a single model to synthesize the information from all the northern fur seal foraging tracks and the available information about the underlying environmental conditions. Application of the approach indicated that the behavioral states for the northern fur seal were significantly related to the Alaska commercial groundfish catch, particularly walleye pollock (Gadus chalogramma).

Bridging the gaps in animal movement: hidden behaviors and ecological relationships revealed by integrated data streams

“…, , Joy et al. , Russell et al. ), these data sources cannot be used for inferences about different types of resting or foraging behavior.…”

“…, Isojunno and Miller , Joy et al. , Russell et al. ) or as covariates in state transition probabilities (e.g., Morales et al.…”

“…, Joy et al. ), but these do not explicitly integrate distinct behavioral state relationships with the environment and state‐switching mechanisms into the movement process.…”

Environmental drivers of demography and potential factors limiting the recovery of an endangered marine top predator

“…Oceanographic conditions are known to be correlated with foraging, health, maternal investment, and reproductive success in pinnipeds. Studies have shown that other otariids, primarily fur seals, associate with certain frontal features while foraging or migrating (Joy et al, 2015; Ream et al, 2005; Speakman et al, 2020; Sterling et al, 2014), but few studies have linked these features to demography. Existing examples include correlations between sea ice and recruitment in Weddell seals (Hadley et al, 2007), SSTs and first‐year survival for subantarctic fur seals ( Arctocephalus tropicalis ; Beauplet et al, 2005), and El Niño conditions and first‐year survival in southern elephant seals ( Mirounga leonina ; McMahon & Burton, 2005).…”

“…This is particularly true for top predators that inhabit vast and heterogenous landscapes, where there is often a mismatch between the ecological question and the data that are available to examine the relevant hypotheses (Conn et al, 2014). Pinnipeds exhibit a range of responses to oceanographic variability, including changes in body condition, reproductive output, maternal attendance patterns, diet, the timing of pupping or weaning, foraging effort, and levels of stranding and mortality (Joy et al, 2015; Speakman et al, 2020; Sterling et al, 2014). While it is important to study these relationships at the scale that is most relevant to the species or ecological process of interest, this is often difficult or impossible to do (Mannocci et al, 2017; Wiens, 1989).…”