Responses to Familiar and Unfamiliar Humans by Belugas (Delphinapterus leucas), Bottlenose Dolphins (Tursiops truncatus), & Pacific White-Sided Dolphins (Lagenorhynchus obliquidens): A Replication and Extension

Abstract

Previous research has documented that cetaceans can discriminate between humans, but the process used to categorize humans still remains unclear. The goal of the present study was to replicate and extend previous work on the discrimination between familiar and unfamiliar humans by three species of cetaceans. The current study manipulated the familiarity and activity level of humans presented to 12 belugas (Delphinapterus leucas) housed between two facilities, five bottlenose dolphins (Tursiops truncatus), and six Pacific white-sided dolphins (Lagenorhynchus obliquidens) during free-swim conditions. Two measures of discrimination were coded from video recordings of each trial: lateralized visual processing and gaze duration. No clear lateralization effects emerged at the species level, primarily due to extensive individual variability. The results also indicated that activity level influenced gaze durations across species, and for some individuals, the interaction between human familiarity and activity level influenced gaze durations and eye preferences. Unexpectedly, bottlenose dolphins had longer gaze durations for familiar humans whereas belugas and Pacific white-sided dolphins had longer gaze durations for unfamiliar humans. All three groups displayed longer gaze durations for active humans as compared to neutral humans, and belugas and bottlenose dolphins had significantly longer gaze durations than Pacific white-sided dolphins. These results indicate that the cetaceans can discriminate between unfamiliar and familiar humans and preferred active humans. However, discrimination of humans via lateralized visual processing did not appear at the group level, but rather at the individual level which countered previous research. This study is discussed within the contexts of attention and individual differences across animals of different species.

Synergy between behavioural research on beluga whales (Delphinapterus leucas) conducted in zoological and wild settings

“…In an extension to that study in captivity, Hill, Yeater et al (2016) also found that belugas looked longer at unfamiliar humans, regardless of their clothing (standardized or uniforms). The captive belugas also exhibited a longer gaze duration for active humans rather than stationary ones.…”

“…That inference that has been supported by follow-up studies conducted in captivity. When studying 12 belugas across multiple zoological facilities both Yeater et al (2014) and Hill, Yeater et al (2016) found lateralized eye preferences at the individual level. In an extension of this line of research, Guarino et al (2017) and Yeater et al (2017) found that belugas tended to view both familiar and novel objects using both eyes, but that they demonstrated a left eye preference when monocular vision was used.…”

Replications, Comparisons, Sampling and the Problem of Representativeness in Animal Cognition Research

“…Again, "same" here does not mean identical, but the same relative to the claim and experimental unit at hand. For example, consider a researcher who wants to compare the relative response of dolphins (e.g., Hill et al, 2016) to familiar and unfamiliar humans with that of elephants (e.g., Polla et al, 2018). Clearly, the researcher must sample from different populations of experimental units [dolphins, elephants], and a different population of settings [aquatic, non-aquatic].…”