Wildlife tourism has little energetic impact on the world's largest predatory shark

Abstract

Wildlife tourism is expanding globally, driving the need to quantify its potential impacts. Studies on the effects of marine tourism on wildlife have focused on documenting behavioural changes, but whether tourism affects the activity levels, energy budgets and ultimately the survival prospects of target animals is largely unknown. To assess the effects of cage diving on the energy expenditure of white sharks, Carcharodon carcharias, animal-borne cameras and accelerometer loggers were deployed on 18 white sharks at a cage-diving site (Neptune Islands Group Marine Park, South Australia) and recorded shark activity for ca. 490 h. A random forest machine-learning model was used to predict their behaviours based on 38 h of acceleration data with behaviours ground-truthed by animal-borne cameras. The presence of cage-diving boats using food-based attractants led to white sharks spending more time undertaking high-energy swimming and bursts of acceleration while decreasing low-energy swimming. However, raised activity during cage-diving operations was not reflected in a substantial shift in energy budgets. Calorific quantification of baits used by the cage-diving industry showed that one bait (tethered southern bluefin tuna, Thunnus maccoyii, gills and entrails) could fuel a white shark for more than a day, which could lead to temporary reduction or cessation of natural foraging, potentially impacting the health and fitness of the individual. Our study reveals new insights into the energetic effects of wildlife tourism on large marine predators. We highlight that while increases in metabolic rate are relatively small for continuously moving predators, the amount of food consumed may impact the health and fitness of individuals and should be considered when managing wildlife tourism activities.

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