Killer whales in South African waters — a review of their biology

  • PB Best
  • MA Meÿer
  • C Lockyer

Abstract

The distribution, seasonality and schooling behaviour of killer whalesOrcinus orca in South African waters have been investigated from 785 records compiled between 1963 and 2009, and their size, morphometrics, growth, reproduction, food and feeding behaviour described from the examination of 54 individuals, 36 of which were landed at the Durban whaling station between 1971 and 1975. Qualitatively, the species appears to be more frequently encountered offshore, where it forms small schools of generally less than six animals. Seasonality of occurrence is not marked, although circumstantial evidence indicates that some individuals migrate from higher latitudes. Males reach 8.81 m and females 7.9 m, with 16.2% of males exceeding the size of the largest female. Stomach content and observational data suggest that the species can be characterised locally as an opportunistic predator of megavertebrates, rather than as the fish-feeding ecotype previously described. A stranded adult male with extreme tooth wear that was 1.5–2 m shorter than other males of equivalent age may be representative of a separate ‘offshore’ ecotype. Apparent differences between features of the popu lation’s life history and those of resident killer whales in the north-eastern Pacific might be attributed to either uncertainties in age determination using dentinal growth layer groups or sampling bias. The basis for the suggestion that killer whales in South African waters should be reclassified as Vulnerable (rather than Data Deficient) is challenged.

Keywords: distribution, feeding, growth, killer whale, morphometrics, Orcinus orca, reproduction, South Africa

African Journal of Marine Science 2010, 32(2): 171–186

Author Biographies

PB Best
Mammal Research Institute, University of Pretoria, c/o Iziko South African Museum, PO Box 61, Cape Town 8000, South Africa
MA Meÿer
Oceans and Coasts, Department of Environmental Affairs, Private Bag X2, Rogge Bay 8012, South Africa
C Lockyer
Age Dynamics, Huldbergs Allé 42, DK2800 Kongens Lyngby, Denmark
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X