Intra-specific aggression is not frequently observed in wild cetaceans, including belugas. One proxy, identified in past research, that indicates past aggressive behaviour is the presence of rake marks (scars left on skin by the teeth of conspecifics). Behavioural observations of belugas, compared to bottlenose dolphins, suggest that belugas engage in less physically aggressive behaviour; yet, a detailed study of beluga aggressive behaviour remains to be conducted. Beluga intra-specific aggression was assessed by scoring photographs taken from July to August in 2015 at Cunningham Inlet, Canada for the presence/absence and body location of rake marks. Of the 252 belugas analysed, 44% had rake marks. The results suggest that physical aggression occurs comparatively less with only half of the observed beluga population having rake marks compared to almost all bottlenose dolphins previously surveyed. We suggest social structure, skin pigmentation, and/or species-specific behaviours as explanations for the differences in rake marks among species.
Personality has now been studied in species as diverse as chimpanzees and cuttlefish, but marine mammals remain vastly underrepresented in this area. A broad range of traits have been assessed only once in each of bottlenose dolphins and California sea lions, while consistent individual differences in a few specific behaviors have been identified in grey seals. Furthermore, the context component of definitions of personality is not often assessed, despite evidence that animals may show individual patterns of behavioral consistency across contexts. The current study therefore aimed to use behavioral coding to assess underlying personality factors and consistency across contexts in two marine mammal species: California sea lions and harbor seals. In both species, two personality factors were extracted using exploratory factor analysis. Both were broadly similar across species; the first, Boldness, resembled human Extraversion, and to some extent Openness, with sea lions exhibiting a greater social component. The second factor was labeled Routine Activity, and may contain some Conscientiousness-like traits. Species-specific patterns were also identified for interactive behaviors across two contexts. However, there was substantial individual variation in the frequency of these behaviors, as well as some animals who did not conform to group-level trends. This study therefore provides novel evidence for broad personality factors and both group- and individual-level patterns of contextual consistency in two pinniped species.
Belugas (Delphinapterus leucas) in managed care have been reported to show seasonal variation in socio-sexual behaviour, hormone levels and respiration rates; however, little is known about the social interactions of wild belugas when they are not in summer, near-shore congregations. To better understand if belugas show seasonal variation in social interactions, this study recorded the behaviour of 10 belugas (five females, five males, ranging from birth to 10 years of age) housed in managed care. Social interactions typically peaked in the summer months but persisted at very low levels during the rest of the year. Seasonal variation was most dramatic for socio-sexual behaviour but was generally mirrored in pattern by agonistic and affiliative interactions. Subjects closer to maturity displayed more seasonal variation than younger subjects, and males displayed more seasonal variation compared to females. The peak in social interactions found in this study aligns rather closely with wild belugas’ summer, near-shore congregations, where belugas have increased opportunities for socializing. Although belugas in managed care do not experience a seasonal change in habitat, they do show seasonal changes in social behaviour, which are likely driven by seasonal fluctuations in hormone levels. It is therefore expected that wild beluga populations would show similar behavioural patterns if they were observed throughout the remainder of the year. This research has applications for belugas in managed care and may provide a framework for understanding the social behaviour of wild belugas.
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