No evidence of time–place learning in juvenile lemon sharks, Negaprion brevirostris

Endogenous circadian clocks coordinate a variety of temporal behavioural aspects in animals, including the daily foraging timing, which is among the most prominent factors that dictate an animal's daily activity patterns. Learning about consistent spatiotemporal patterns in food availability can be advantageous, as it may increase foraging efficiency. Time–place learning abilities have been demonstrated in teleosts but has yet to be studied in chondrichthyans. Understanding time–place learning in sharks will help us understand how anthropogenic factors, including wildlife tourism, may affect shark behaviour. Here, we investigated the ability of sharks to learn time–place associations in a semicontrolled environment. We fed juvenile lemon sharks at two different locations at two distinct times of day inside 45 m² enclosures for 41 days, and monitored their learning along with untrained, control individuals. We used time-lapse recordings to assess a shark's position relative to the upcoming feeding location. Based on the mean distance to the feeding location and the time sharks spent within three body lengths of it we concluded that they did not learn the association. Sharks in the treatment pens displayed distribution patterns similar to those of the control sharks throughout the experiment. The position of the sharks inside the pens appeared to be significantly affected by the tidal cycle. We were unable to detect time–place learning within the limited time of the experiment possibly due to the small size and space between the enclosures, and the influence of the tidal cycles.