Coastal, offshore, and migratory movements of South African right whales revealed by satellite telemetry

摘要

In September 2001, 21 satellite-monitored radio tags were deployed on southern right whales in South African waters, 15 of which transmitted for 25-161 d. Most coastwise movement on the south coast occurred in a westerly direction with cow-calf pairs moving slowest. Three whales tagged on the west coast and one tagged on the south coast moved north into St Helena Bay, a probable feeding ground, where residence times were 36-100 d. Five animals tracked after leaving the coast maintained a bearing of 201 degrees-220 degrees before branching out over the southeast Atlantic from 37 degrees to 60 degrees S and between 13 degrees W and 16 degrees E, traveling 3,800-8,200 km over the ensuing 53-110 d before transmissions ceased. Their locations were categorized as migrating or nonmigrating based on the relative orientation of the track and net speed. An average of 42% of nonmigrating locations were between 37 degrees S and 45 degrees S, and 53% were south of 52 degrees S, possibly associated with the Subtropical Convergence and Antarctic Polar Front, respectively. Whaling data suggest right whales fed largely on copepods at the former and euphausiids at the latter. If the nonmigrating locations represented feeding at these frontal zones, switching between them would seem to have obvious cost-benefit implications.