Date of Award

5-16-2025

Publication Type

Dissertation

Degree Name

Ph.D.

Department

Biological Sciences

Keywords

behavioural ecology; cetacean; contact call; disturbance; social structure; vocal communication

Supervisor

Daniel J. Mennill

Supervisor

Valeria Vergara

Rights

info:eu-repo/semantics/openAccess

Abstract

Much can be learned by carefully listening to animals. This is particularly true for animals that produce complex vocalizations that vary between individuals or social groups. By examining the contexts in which these sounds are produced and variation in the acoustic features across locations, we can better understand how animals experience the world and how human activities impact their lives. Belugas, Delphinapterus leucas, one of the most loquacious cetaceans, produce complex contact calls that provide a key opportunity for such insights. The goal of my dissertation was to investigate the vocal and social behaviour of belugas, as well as the impacts of human activities on their behaviour. This dissertation includes five data chapters (Chapters 2-6). In Chapter 2, I reviewed the social structure of belugas and examine evidence of culture in beluga populations. Evidence indicates that beluga societies tend to be structured by atomistic, individual-based fission-fusion dynamics and that most beluga societies are sexually-segregated, with male groups often forming close, long-lasting associations. Growing evidence suggests that female beluga sociality may be best defined as “matrifocal” rather than “matrilineal”. I discussed the strong evidence for migratory culture in belugas and emphasized a need for further research on vocal culture. In Chapter 3, I examined the impacts of unoccupied aerial vehicles (i.e., drones) on endangered St. Lawrence belugas across a range of different conditions. I found that belugas were most likely to show evasive reactions during low-altitude drone flights, particularly below 23m. My findings indicated that evasive reactions are particularly likely during initial approaches to a group of whales, and during flights over larger groups. I reviewed drone studies of cetaceans to identify altitude thresholds linked to disturbance, and found that reactions to drones were most common at flight altitudes below 30 m. I formulated seven recommendations for researchers using drones to study cetaceans. In Chapter 4, I examined the contexts in which free-living St. Lawrence belugas produced complex contact calls. I showed that contact call production changed across different socio-behavioural contexts. My results showed that contact call production increased in large herds, in herds engaged in milling or multidirectional behaviour, and in herds with an intermediate level of dispersion. Notably, contact call production decreased as large vessel traffic increased, highlighting the impact of anthropogenic disturbance on beluga vocal behaviour. In Chapter 5, I used passive acoustic monitoring of distinctive contact calls to quantify the spatial structure of the St. Lawrence beluga population. Using a mark-recapture-based analysis of beluga complex contact calls over a five-year period, I identified two distinctive communities, one centered on the Saguenay Fjord (the Saguenay community), and one centered on the south shore of the Upper Estuary (the South Shore community). This finding suggests that the Saguenay-St-Lawrence Marine Park should be expanded to include the ranges of both communities to better protect the St. Lawrence beluga population. In Chapter 6, I examined vocal variation between the contact calls of the two communities and suggested that these differences represent community-specific vocal dialects, although further research is needed to support this conclusion. My findings showed that the signature elements of calls from the South Shore community tended to be more frequency-modulated, covered a narrower range of frequencies, and peaked at higher frequencies than those from the Saguenay community. However, Saguenay community calls exhibited greater energy in higher frequencies than calls from the South Shore community. Some of these differences may reflect adaptations to the acoustic environment of each community. Collectively, my research highlights the vocal, social, and cultural complexity of belugas and underlines the impacts of humans on their behaviour.

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