| Summary: | The remote, ice-covered habitat and reclusive nature of Arctic cetaceans have led to a gap in knowledge about species ecology. In rare instances where Arctic cetaceans can be spotted, information about their population structure and biology can be gleaned through observation; however, direct observations are difficult in high ice cover. Ice entrapments, where cetaceans are crowded under increasing ice cover until escape or drowning, have given insight into cetacean populations since the 18th century, and today new genetic analyses can allow us to reexamine the population structure of these Arctic species and add to previous research on ice entrapments and narwhal social structure. In this thesis’ second chapter, I first review 138 cetacean ice entrapment occurrences globally and show that ice entrapments are a significant source of mortality for cetaceans, killing more than 18,500 individuals in 13 different species since 1900. In the third chapter, I use population genetics to study the social structure of the Canadian Arctic narwhal (Monodon monoceros) from a 2008 ice entrapment. Through pair-wise relatedness and cluster analysis, I determined that within an ice-entrapped herd (n=245), there were 8 genetically related clusters with an average size of 30.6, indicating that the species may follow a fission-fusion social structure like other smaller, social cetaceans. This work may contribute to species management decisions and be valuable for emergency management of ice entrapments. May 2024
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