Abstract:
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 201-220o before branching out over the southeast Atlantic from 37-60o S
and between 13o W and 16o E, travelling 3800-8200 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 non-migrating locations were between 37-45o S and 53% south of 52o S,
possibly associated with the Sub Tropical 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 non-migrating locations represented feeding at
these frontal zones, switching between them would seem to have obvious cost-benefit
implications.
