Swimming strategies and energetics of endothermic white sharks during foraging

• DOI: 10.1242/jeb.185603
• Publication Date: 2019-02-19T04:15:11Z
• Authors: Yuuki Y. Watanabe; Nicholas L. Payne; Jayson M. Semmens; Andrew Fox; Charlie Huveneers
• Keywords: Energetics; Carcharias; Ectotherm; Optimal foraging theory

ABSTRACT Some fishes and sea turtles are distinct from ectotherms by having elevated core body temperatures metabolic rates. Quantifying the energetics activity of regionally endothermic species will help us understand how a fundamental biophysical process (i.e. temperature-dependent metabolism) shapes animal ecology; however, such information is limited owing to difficulties in studying these large, highly active animals. White sharks, Carcharodon carcharias, largest fish with regional endothermy, potentially among most energy-demanding fishes. Here, we deployed multi-sensor loggers on eight white sharks aggregating near colonies long-nosed fur seals, Arctocephalus forsteri, off Neptune Islands, Australia. Simultaneous measurements depth, swim speed (a proxy for swimming rate) acceleration (indicating when exhibited energy-efficient gliding behaviour) revealed their fine-scale behaviour allowed estimate energy expenditure. Sharks repeatedly dived (mean 29 m) swam at surface between deep dives (maximum 108 m). Modal speeds (0.80–1.35 m s−1) were slower than estimated that minimize cost transport (1.3–1.9 s−1), pattern analogous ‘sit-and-wait’ strategy perpetually species. All but one shark employed unpowered during descents, rendering (>50 29% less costly swimming, which may incur additional wave drag. We suggest behavioural strategies maximize net gains reducing while increasing encounter rates fast-swimming seals.