Post-prandial visceral warming in free-swimming white sharks, Carcharodon carcharias

Abstract

Context The movement patterns in animals are influenced by their physiological demands and the response to external cues. Aims Determined how meal size and quality affect the heat generated during digestion. Methods This study actively tracked seven white sharks (1.7–4.2 m in total length) off Mossel Bay (South Africa) for approximately 700 h, recording the external (ambient) and internal (body) temperatures. Key results Our findings show that white sharks elevate their stomach temperature after the ingestion of a meal, reaching values of 27–30°C while swimming in waters of 13–19°C. A stomach thermal excess of up to 16°C lasted from 12 to 36 h before returning to a basal temperature of 7–13°C above ambient. These thermal data were used to quantify the heat increment of feeding (HIF, as a relative proxy for the energetic output of digestion) and suggest that shark size may affect the thermal response, when digesting a meal of similar size and energetic content. In addition, thermal data from a single individual that ingested several meals with different energetic content show marked changes in the HIF responses, with the digestion of more complex (i.e. energetically rich) meals showing higher and prolonged HIF events. Conclusions The capacity to reach elevated stomach temperatures after feeding and the potential effect of body size on stomach thermal excess, coupled with more efficient swimming kinematics, may underscore the capacity of white sharks, especially larger individuals, to effectively expand their niche into colder waters and better exploit areas where more energetically-rich prey are present.