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Daily and seasonal movements of cape cod gray seals vary with predation risk

Publication ,  Journal Article
Moxley, JH; Skomal, G; Chisholm, J; Halpin, P; Johnston, DW
Published in: Marine Ecology Progress Series
June 25, 2020

White sharks Carcharodon carcharias and gray seals Halichoerus grypus are reestablishing their ecological roles within the Northwestern Atlantic Ocean, presenting an opportunity to understand gray seal movement and at-sea behavior under predation risk. As with other shark-seal hotspots, movements to and from terrestrial haul outs can be risky for gray seals, thereby eliciting antipredator strategies. We investigated the movement and coastal behavior of gray seals on Cape Cod (USA) in relation to seasonal and diel changes in white shark activity. Analyzing 412 trips to sea by 8 seals and more than 25 000 acoustic detections from 23 individual white sharks, we observed seasonally homogeneous movements in seal behavior during months with greater shark presence. During riskier months, seal behavior manifested in near-exclusive nocturnal foraging, reduced offshore ranging, and limited at-sea activity. On these nocturnal trips to sea, seals returning to haul outs tended to avoid daybreak and traversed during diel minima in shark activity. However, seals tended to depart haul outs at dusk when shark presence was maximal. As conservation efforts succeed in rebuilding depleted populations of coastal predators, studying re-emerging predator-prey interactions can enhance our understanding about the drivers of movement and behavior.

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Published In

Marine Ecology Progress Series

DOI

ISSN

0171-8630

Publication Date

June 25, 2020

Volume

644

Start / End Page

215 / 228

Related Subject Headings

  • Marine Biology & Hydrobiology
  • 4102 Ecological applications
  • 3109 Zoology
  • 3103 Ecology
  • 0608 Zoology
  • 0602 Ecology
  • 0405 Oceanography
 

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Moxley, J. H., Skomal, G., Chisholm, J., Halpin, P., & Johnston, D. W. (2020). Daily and seasonal movements of cape cod gray seals vary with predation risk. Marine Ecology Progress Series, 644, 215–228. https://doi.org/10.3354/meps13346
Moxley, J. H., G. Skomal, J. Chisholm, P. Halpin, and D. W. Johnston. “Daily and seasonal movements of cape cod gray seals vary with predation risk.” Marine Ecology Progress Series 644 (June 25, 2020): 215–28. https://doi.org/10.3354/meps13346.
Moxley JH, Skomal G, Chisholm J, Halpin P, Johnston DW. Daily and seasonal movements of cape cod gray seals vary with predation risk. Marine Ecology Progress Series. 2020 Jun 25;644:215–28.
Moxley, J. H., et al. “Daily and seasonal movements of cape cod gray seals vary with predation risk.” Marine Ecology Progress Series, vol. 644, June 2020, pp. 215–28. Scopus, doi:10.3354/meps13346.
Moxley JH, Skomal G, Chisholm J, Halpin P, Johnston DW. Daily and seasonal movements of cape cod gray seals vary with predation risk. Marine Ecology Progress Series. 2020 Jun 25;644:215–228.
Journal cover image

Published In

Marine Ecology Progress Series

DOI

ISSN

0171-8630

Publication Date

June 25, 2020

Volume

644

Start / End Page

215 / 228

Related Subject Headings

  • Marine Biology & Hydrobiology
  • 4102 Ecological applications
  • 3109 Zoology
  • 3103 Ecology
  • 0608 Zoology
  • 0602 Ecology
  • 0405 Oceanography