Behavioral Ecology and Sociobiology

, Volume 69, Issue 1, pp 127–138

The role of refugia in reducing predation risk for Cape fur seals by white sharks

  • Michelle Wcisel
  • M. Justin O’Riain
  • Alta de Vos
  • Wilfred Chivell
Original Paper

DOI: 10.1007/s00265-014-1825-5

Cite this article as:
Wcisel, M., O’Riain, M.J., de Vos, A. et al. Behav Ecol Sociobiol (2015) 69: 127. doi:10.1007/s00265-014-1825-5

Abstract

Refugia play an important role in shaping predator/prey interactions; however, few studies have investigated predator–prey relationships between large marine vertebrates, mainly due to the logistical challenges of studying marine species. The predictable interactions between Cape fur seals and white sharks in South Africa at two neighbouring seal colonies (Seal Island and Geyser Rock) with similar breeding conditions, but distinct adjacent seascapes, offer an opportunity to address this gap. Geyser Rock differs from Seal Island in being surrounded by abundant refugia in the form of kelp beds and shallow reefs, while Seal Island is mostly surrounded by deep open water. In this study, we compare data collected from Geyser Rock to the published data at Seal Island and ask, do seals adjust their anti-predator tactics as a function of landscape features? We found that during periods of high white shark presence, seals at Geyser Rock reduced their presence in open-water and utilized areas that contained complex landscapes around the colony. Although seals at Geyser Rock formed groups when traversing open water, neither group size (high risk median = 4, low risk median = 5) nor temporal movement patterns varied significantly with white shark presence as has been shown at Seal Island. Furthermore, recorded hourly predation rates at Seal Island were 12.5 times higher than at Geyser Rock. Together, these findings suggest that refuge use may be the more effective anti-predator response of seals to a seasonally abundant predator and that the predations at Seal Island reflect a comparative lack of refugia.

Keywords

Arctocephalus pusillus pusillus Carcharodon carcharias Dyer Island Refuge use Anti-predator tactics Shark Alley 

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Michelle Wcisel
    • 1
    • 2
  • M. Justin O’Riain
    • 2
  • Alta de Vos
    • 2
  • Wilfred Chivell
    • 1
  1. 1.Dyer Island Conservation TrustGansbaaiSouth Africa
  2. 2.Department of Biological SciencesUniversity of Cape TownCape TownSouth Africa