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 whal es. Sowerby's Beaked Whale (Mesoplodon bidens) is known from only a handful of sightings and strandings; few descriptions of group composition or surf acing behaviour are available. During 1997 and 1998, groups of Sowerby's Be aked Whales were observed in the Gully, a submarine canyon off eastern Cana da, on four occasions. Sightings were in water depths of between 550 and 15 00 m. Group size varied from 3 to 8-10 individuals. A mixed composition gro up was observed on one occasion, consisting of at least two female-calf pai rs 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 be tween 12 and 28 minutes. Blows were either invisible or relatively inconspi cuous. During all surfacings the long beak projected from the water well be fore the rest of the head or back was visible. While surfacing behaviour wa s generally unremarkable, one individual tail-slapped repeatedly.