Observations of Sowerby's Beaked Whales, Mesoplodon bidens, in the Gully, Nova Scotia

Little is known about most members of the family Ziphiidae, the beaked whales. Sowerby's Beaked Whale (Mesoplodon bidens) is known from only a handful of sightings and strandings; few descriptions of group composition or surfacing behaviour are available. During 1997 and 1998, groups of Sowerby's Beaked Whales were observed in the Gully, a submarine canyon off eastern Canada, on four occasions. Sightings were in water depths of between 550 and 1500 m. Group size varied from 3 to 8-10 individuals. A mixed composition group was observed on one occasion, consisting of at least two female-calf pairs and two to four adult males (based on the presence of visible teeth and extensive scarring). Another group consisted of three quite heavily-scarred and therefore presumably male animals. Whales were observed to dive for between 12 and 28 minutes. Blows were either invisible or relatively inconspicuous. During all surfacings the long beak projected from the water well before the rest of the head or back was visible. While surfacing behaviour was generally unremarkable, one individual tail-slapped repeatedly.