Fine-scale variability in harbor seal foraging behavior

A 2014 paper in the journal PLoS ONE examines differences between foraging behavior of harbor seals based on haulout site locations, seasons, sexes and times of day. The authors hypothesize that these factors may help explain the variability in diet among harbor seals observed at different haul-out site groups in the Salish Sea. 

Harbor seals, Lopez Island, WA. Photo: Bethany Weeks (CC BY-NC 2.0) https://flic.kr/p/6Mnq5k
Harbor seals, Lopez Island, WA. Photo: Bethany Weeks (CC BY-NC 2.0) https://flic.kr/p/6Mnq5k

Summary

Harbor seals in the Salish Sea utilize and haul-out on multiple habitat types including estuarine bays and rocky reefs. We instrumented seals from two distinct sites with Time Depth Recorders to investigate their dive behavior on a fine spatial scale. We identified three behavioral bout types that were classified from six dive types within each bout: Deep foraging bouts (Type I), shallow foraging or traveling bouts (Type II), and haul-out activity (Type III). Type I bouts were the most common and were used throughout the study by seals from both sites. The proportional use of Type I and Type II (shallow foraging/traveling) bouts differed dramatically between haul-out sites, seasons, sexes, and whether it was day or night. Harbor seals also demonstrate a lot of individual variation in their behavior so this likely contributed to the observed differences as well. We hypothesized that the variation in dive behavior that we observed was related to habitat or prey specialization by seals from different haul-out sites/habitats, or individual variability between the seals themselves. These results highlight the potential influence of habitat and specialization on the foraging behavior of harbor seals, and may help explain the variability in diet that is observed between different haul-out site groups in the Salish Sea.

Citation

Wilson K, Lance M, Jeffries S, Acevedo-Gutiérrez A (2014) Fine-Scale Variability in Harbor Seal Foraging Behavior. PLoS ONE 9(4): e92838. https://doi.org/10.1371/journal.pone.0092838

Download the full article (open access)

About the Author: 
Kenady Wilson, Western Washington University; Monique Lance, Washington Department of Fish and Wildlife; Steven Jeffries, Washington Department of Fish and Wildlife; Alejandro Acevedo-Gutiérrez, Western Washington University