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Port Adelaide, Australia

Robbins R.,Fox Shark Research Foundation | Fox A.,Fox Shark Research Foundation
Marine and Freshwater Research

Patterns of pigmentation are widely used for the identification of white sharks, with photographic databases often forming the basis for studies of population modelling, site fidelity and movement patterns. The permanence of these identifying markings is assumed to remain constant. Here, we present evidence of melanism resulting in a change in the shape and size of pigmentation markings on the lower caudal lobe of a female white shark. We found a 33% reduction in size of an islet over a 9-month period. The newly melanised region was 10% darker than the adjoining pigmented areas, and did not match the original pattern. Possible causes of the observed melanism are presented, and the implications for the reliability of using caudal-fin pigmentation patterns for identification purposes are discussed, with a combinational matching approach recommended. © 2012 CSIRO. Source

Huveneers C.,Flinders University | Huveneers C.,South Australian Research And Development Institute | Holman D.,Flinders University | Robbins R.,Fox Shark Research Foundation | And 3 more authors.
American Naturalist

There is no conclusive evidence of any nonhuman animal using the sun as part of its predation strategy. Here, we show that the world’s largest predatory fish—the white shark (Carcharodon carcharias)—exploits the sun when approaching baits by positioning the sun directly behind them. On sunny days, sharks reversed their direction of approach along an east-west axis from morning to afternoon but had uniformly distributed approach directions during overcast conditions. These results show that white sharks have sufficient behavioral flexibility to exploit fluctuating environmental features when predating. This sun-tracking predation strategy has a number of potential functional roles, including improvement of prey detection, avoidance of retinal overstimulation, and predator concealment. © 2015 by The University of Chicago. All rights reserved. Source

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