Study Finds That Great White Sharks Really Stress-Out Seals

A little stress can be good, but new study shows cape fur seals living in sharky waters off South Africa aren't well.

While a little added stress may be helpful to flee a dangerous situation, or to meet an approaching deadline, it’s no secret that prolonged exposure to the stress hormone cortisol is linked to health problems. So, what effects does stress have on animals in the wild that need to navigate the same waters as the ocean’s top predator—great white sharks?

Predators are known to impact the population abundances of their prey by killing and consuming them. But can predators in the wild also exert control over their prey from the stress associated with living in high-risk waters?

University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science-led research team found just the right situation—fur seals living among one of the densest populations of great white shark off South Africa’s Western Cape—to test this predation-stress hypothesis in the wild.

In the three-year study, the scientists focused their investigation on six islands in the region where Cape fur seals (Arctocephalus pusillus) colonies have varied seasonal exposure to hunting great white sharks (Carcharodon carcharias).

Photo: Elias Levy/Wikimedia Commons (CC BY 2.0)

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