The aim of this study was to determine whether California sea lions ( Zalophus californianus ) are capable of using subtle human gestural cues in a series of object choice tests. Four sea lions, housed at  Parc Astérix Dolphinarium (Plailly, France), were tested using three gestural cues: hip-based finger points, chest-based finger points and eye glances (no head movement involved). Above chance performance was found in response to these cues in 4/4, 2/4, and 1/4 sea lions, respectively, suggesting that the sea lions were able to generalize their response from conspicuous pointing gestures to subtle finger pointing, as well as to eye glance cue for one subject. Discrepancies in accuracy rates between the cues confirmed however that conspicuousness of the pointing gesture is determinant for the ability of the sea lions to exploit it efficiently. These findings reinforce the hypothesis that human-socialization of undomesticated species can lead some individuals to develop an affinity for interpreting very subtle human gestural cues.

Exploratory behavior includes all the actions that an animal performs to obtain information about a new object, environment, or individual through using its different senses of perception. Here, we studied the development of the exploratory behavior of a bottlenose dolphin (Tursiops truncatus) calf aged from 39 to 169 days by investigating its acoustic productions in relation to an immersed object handled by a familiar human without without the calf being isolated from the original social group. The study was conducted between July 2015 and January 2016 at Parc Asterix dolphinarium (Plailly, France). Simultaneous audio and video recordings were collected using a waterproof 360° audio-video system named BaBeL, which allows localization of the dolphin that is producing sounds. During 32 recording sessions, for a total duration of 6 hr 55 min of audio-video recordings, 46 click trains were attached to individual dolphins: 18 times to the calf, 11 times to its mother, and 17 times to another dolphin in the pool. When comparing the calf’s acoustical production to its mother’s, no significant differences were found in their click rate, mean click duration, or mean interclick interval (ICI). However, linear regression showed that calfs’ click rates increased with age and mean ICI decreased with age, probably due to an increase in its arousal. This nonintrusive methodology allows the description and analysis of acoustic signal parameters and acoustic exploratory behavior of a dolphin calf within its social group.