FEEDING HABITS AND POSSIBLE MOVEMENTS OF SOUTHERN BOTTLENOSE WHALES (HYPEROODON PLANIFRONS) (14th Symposium on Polar Biology)
Stomach contents of two southern bottlenose whales (Hyperoodon planifrons) were examined in detail; a 6.43 m male caught off the east coast, and a 6.55 m lactating female stranded alive on the west coast of South Africa. Both stomachs contained only squid remains. All lower squid beaks were counted (1995 in the male, 1912 in the female), each beak was identified, and the original dorsal mantle length and weight were calculated. A total of 36 species in 14 families of squids was identified, all of which were oceanic species. Four Antarctic squids (Kondakovia longimana, Galiteuthis glacialis, Alluroteuthis antarcticus and Mesonychoteuthis hamiltoni) and four subantarctic species (Gonatus antarcticus, Moroteuthis knipovitchi, Moroteuthis ingens and Histioteuthis eltaninae) were present. In weight percentage, the stranded female had more Antarctic and subantarctic squids in its stomach (72.4%) than the captured male (43.7%), but by number both animals contained similar percentages (28.1% for the female and 29.2% for the male). The rest of the squid species found in the stomachs may occur in South African waters. Sightings of southern bottlenose whales off Durban between February and October showed strong seasonality with peaks in February and October. The beaks of Antarctic and subantarctic squids in the stomachs, plus the presence of cold water skin diatoms Bennettella [=Cocconeis] ceticola on the male, suggest that the animals had arrived comparatively recently in South African waters from higher latitudes. Therefore, the February peak in sightings might represent a northward movement of southern bottlenose whales from the Antarctic.