Abstract:
Three Heaviside’s dolphins Cephalorhynchus heavisidii were fitted with satellite depth recorders off the west
coast of South Africa during February–April 1997 and monitored for 51, 73 and 130 days, respectively. In total,
345 locations were received from the three animals, but only 27 from one male. Using -local convex hull and
minimum convex polygon methods, respectively, the home range for the remaining male was estimated at 1 520 and
2 347 km2, with corresponding core-area estimates (50% of locations) of 134 and 123 km2. For the female, the home
range estimates were 672 and 1 027 km2, and those for the core area were 71 and 230 km2. The female’s home range
was the smallest yet described for this species, and the animal was resighted nearly three years later within 13 km
of the tagging site. Binned dive data were received at 6-hourly intervals. From comparison of maximum dive depth
and time-at-depth data, we concluded that dives <4 m deep were associated with surfacing bouts. Dives to below
4 m occurred throughout 24 h but were shallower during the day and deepest either at dusk or at night. This pattern
was consistent with earlier descriptions of offshore movement during the day and may be related to the diel vertical
migration of its principal prey, shallow-water hake Merluccius capensis.
