Using underwater images to sample and determine trends in lateralization and group counts when beluga calves and juveniles are present
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Date
2022-08-25
Authors
Ince, Danielle
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Abstract
In this thesis, I used underwater images to determine patterns in lateralization and group size when beluga calves and juveniles are present. Usually, lateralization is defined by either a left or right preference, but using underwater images (an untested, non-invasive approach) provided an opportunity to analyze position bias from three distinct planes, the sagittal (left or right), coronal (dorsal or ventral), and transverse (anterior or posterior). My research found that the presence of the boat may have affected lateralization as juveniles were most frequently observed on the left. This position bias was possibly due to their mothers, who may have positioned themselves between their young and the less familiar boat. Additionally, while both calves and juveniles preferred to be positioned in ventral positions near their mother, juveniles were most frequently observed at the anterior of the head region, while calves were in the posterior or tail region or infant position. This difference is likely due to juveniles having increased swimming abilities, allowing them to compromise the hydrodynamic benefits of the infant position for the anterior position, as the head or anterior is preferred for social interactions in whales. In my second chapter, I determined if mother and calf/juvenile dyads selected larger groups. My results indicated that groups that contained calves and juveniles had more adults present than groups that contained adults only. In comparison with aerial surveys, I found that group sizes in underwater images were significantly larger across all age classes. This may be an effect of methods used, as boats used to collect camera images may have moved to locations where beluga were aggregating. However, further research is needed to determine the effect of boats on juveniles’ interactions.
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Keywords
Beluga, Churchill, Manitoba, Lateralization, group structure, group composition, underwater camera