Do Belugas (Delphinapterus leucas), Bottlenose Dolphins (Tursiops truncatus), & Pacific White-Sided Dolphins (Lagenorhynchus obliquidens) Display Lateralized Eye Preference when Presented with Familiar or Novel Objects?

Abstract

Lateralization of behaviors and information processing are common across species. Hypothesized to be crucial for more efficient responding to environmental stimuli, lateralization has been investigated for a number of topics. Cetaceans are proposed to be hemispheric specialists, given a small corpus callosum, complete decussation of the optic nerve, and the ability to respond to a different visual stimulus presented to each eye simultaneously. Research with cetaceans has shown strong biases in a number of behaviors, including swimming, foraging, social interactions, and responses to myriad visual stimuli. Given similar evolutionary pressures, different species of cetaceans should display similar lateralized preferences. Previous research with bottlenose dolphins in managed care and wild striped dolphins indicated a right eye preference when viewing unfamiliar objects. The purpose of the current study was to evaluate the eye preference of belugas, bottlenose dolphins, and Pacific white-sided dolphins (lags) in managed care when viewing familiar and unfamiliar objects. The results from 11 belugas, 5 bottlenose dolphins, and 5 lags indicated that consistent group level eye preferences were not present. The belugas preferred to view both types of objects with both eyes, with the majority of the belugas showing a left-eye preference when a monocular gaze was used. Bottlenose dolphins tended to view both objects with their right eye while lags used their left eye when viewing objects. These results may have been affected by viewing objects below water versus above water. The belugas and the Pacific white-sided dolphins were able to view the objects below water, which may have elicited more naturalistic visual examinations of the objects (i.e., greater ecological validity). Viewing objects within one’s habitat may facilitate the discrimination of an object rather than simply its detection, which is may be more likely when encountering stimuli above the surface of the water as the bottlenose dolphins had to do in the present and past research. Future research should compare if presentation of the stimulus above water versus below water affects the eye preference displayed.