Hal's work is principally on the behaviour, social structure, population biology and conservation of sperm whales, techniques of studying social structure, and more general questions about social structure in mammals and cultural evolution.

His Cetacean Research Group at Dalhousie University conducts research on the culture, behavioural ecology, social organisation, ranging behaviour, distribution, population biology, acoustic behaviour and conservation of several cetacean species, particularly the sperm whale, northern bottlenose whale, and the long-finned pilot whale.

Hal is currently supervising Christine Konrad and Wilfried Beslin during their masters research.