Aggregation size of Bryde’s whales was positively correlated
with the occurrence of feeding behaviour in this study. This
was similar to the situation in the Gulf of California, where
solitary individuals were usually travelling, whereas aggregations
of comparable sizes to those found in this study during
summer and autumn were associated with feeding (Tershy
1992). During winter there are increased sightings of Bryde’s
whales farther north along the East Coast, frequently in
groups with common dolphins and Cape gannets (Best et al.
1984, Best 2001, O’Donoghue et al. 2010b). This appears
to coincide with the annual north-eastward migration of
sardine into KwaZulu-Natal waters (Fréon et al. 2010). Thus,
movements of animals away from the study area in pursuit
of prey during the sardine run could have contributed to the
observed temporal differences in encounter rates, aggregation
size, interspecific interactions, and feeding behaviour of
Bryde’s whales in our study.