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

Michelle Jewell michellewcisel at gmail.com
Sun Oct 26 11:46:47 PDT 2014

Dear MARMAM subscribers,

We are very happy to bring our latest publication to your attention that
documents refuge use by the Cape fur seal *Arctocephalus pusillus pusillus*.

Wcisel, M., O’Riain, M. J., de Vos, A., & Chivell, W. (2014). The role of
refugia in reducing predation risk for Cape fur seals by white sharks.
Ecology and Sociobiology* (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.

Full text: http://www.springer.com/-/9/fb2e3c345c5c448799fae19a765b6090

All the best,

Michelle Jewell (Wcisel)
B.Sc., M.Sc. Zoology
Email: michellewcisel at gmail.com
Skype: MichelleWcisel
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