Movement of bottlenose dolphins around the south-west coast of Britain

Abstract

After an absence of two decades a group of bottlenose dolphins, Tursiops truncatus, became resident in the coastal waters of Cornwall, U.K. in 1991. Using a combination of field techniques and information from the general public, the movements of this group were monitored. The dolphins demonstrated a seasonal residency pattern, spending the winter in southern Cornwall and moving further north-eastward during spring and summer. Residency was flexible with a number of individual dolphins using the region intermittently. The dolphins occupied a linear range of coast of 650 km. Within this range they repeatedly made long-distance journeys. Mean swimming speed was documented at 7.9 km·h⁻¹, with the dolphins travelling the coast at a mean of 3.6 km·h⁻¹. The longest journey recorded covered 1076 km and took 20 days. In one confirmed case the dolphins left the south-west of England and were resighted in Wales. Such wide ranging movements have important implications for the conservation of bottlenose dolphins in U.K. waters.