Shark habituation to a food-related olfactory cue

Learning is a process that allows animals to develop adaptive behavioural responses to novel situations within an individual's lifetime. The simplest form of learning, habituation, acts a fundamental filter mechanism, which allows animals to ignore irrelevant recurring stimuli, thereby freeing up fitnessrelated resources, such as time and energy, as well as neural capacity. Although earlier studies have demonstrated that habituation occurs in a variety of taxa ranging from insects to mammals, our knowledge of this process in elasmobranchs is limited. Sharks and rays face an increasingly popular shark-diving industry, so it is important to understand how sharks respond to attractants used by tourism operators. Our study investigated whether sharks habituate to the smell of a potential food source, which has been proposed as a sustainable alternative to actively feeding sharks. We exposed 11 captive juvenile sharks individually to the smell of squid for 4 min, three times per day for 21 days in the absence of a food reward. We found declining responses to the stimulus within and across daily exposure sessions, indicating both short- and long-term habituation. Our findings suggest that sharks learn to avoid wasting time and energy on inaccessible food sources. Given the decreasing response observed in our study, the use of olfactory cues only may have limitations in its efficacy to attract sharks for tourism purposes. Habituation may act as a driver of optimal foraging strategies, enabling sharks to quickly abandon low-yielding foraging patches in search of more productive sites.(c) 2022 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.