Behavioural laterality in foraging bottlenose dolphins ( Tursiops truncatus )

Abstract

Lateralized behaviour is found in humans and a wide variety of other species. At a population level, lateralization of behaviour suggests hemispheric specialization may underlie this behaviour. As in other cetaceans, dolphins exhibit a strong right-side bias in foraging behaviour. Common bottlenose dolphins in The Bahamas use a foraging technique termed ‘crater feeding’, in which they swim slowly along the ocean floor, scanning the substrate using echolocation, and then bury their rostrums into the sand to obtain prey. The bottlenose dolphins off Bimini, The Bahamas, frequently execute a sharp turn before burying their rostrums in the sand. Based on data collected from 2012 to 2018, we report a significant right-side (left turn) bias in these dolphins. Out of 709 turns recorded from at least 27 different individuals, 99.44% (n = 705) were to the left (right side and right eye down) [z = 3.275, p = 0.001]. Only one individual turned right (left side and left eye down, 4/4 turns). We hypothesize that this right-side bias may be due in part to the possible laterization of echolocation production mechanisms, the dolphins' use of the right set of phonic lips to produce echolocation clicks, and a right eye (left hemisphere) advantage in visual discrimination and visuospatial processing.

Population-Level Laterality In Foraging Finless Porpoises

“…At several locations in the United States and Mexico, strand feeding common bottlenose dolphins (Tursiops truncatus) have been observed to chase sh onto the beach on the right side of their body 8, 9 . Similar right-side down feeding postures have been reported in bottlenose dolphins in Florida Keys (plume-feeding, 10 ) and in the Bahamas (crater-feeding, 11 ). Killer whales (Orcinus orca) lunge-feeding for salmon in Kamchatka, Russia, also show the same right-side bias 2 .…”

“…This is mainly due to the asymmetry in the size of the phonic lips and air sacs associated with sound production 25 . This morphological asymmetry has been considered to be a cause of the behavioral asymmetry of delphinids 11 . However, this asymmetry is much smaller in phocoenids (including nless porpoises) and the asymmetry of the sound beam is biased slightly toward the left, although the difference is not signi cant 26,27 .…”

“…A few theories have been suggested to explain this right-side bias in the cetacean foraging behavior; sensory processing (visual processing in particular), laterality in the cerebral hemisphere, asymmetry of echolocation signals, and the morphological laterality in the larynx 2,11 . It is widely accepted that differences in sensory processing between the cerebellar hemispheres cause behavioral laterality in various vertebrates 3 .…”

“…Killer whales (Orcinus orca) lunge-feeding for salmon in Kamchatka, Russia, also show the same right-side bias 2 . In general, these behavioral asymmetries are attributed to the use right eye -and thus, the left hemisphere of the brain-to gain and process information regarding prey 2,11 .…”

Laterality of Eye Use by Bottlenose (Tursiops truncatus) and Rough-Toothed (Steno bredanensis) Dolphins While Viewing Predictable and Unpredictable Stimuli

“…In wild settings, laterality of feeding behavior has been noted in diverse species of cetaceans. Lunging or rolling to the right side to capture prey has been observed in North Atlantic humpback whales (Megaptera novaeangliae; Canning et al, 2011), gray whales (Eschrichtius robustus; Woodward & Winn, 2006), bottlenose dolphins (Kaplan et al, 2019), and orcas (Karenina et al, 2016).…”