Abstract:
Killer whales, Orcinus orca, are top predators occupying key ecological roles in a
variety of ecosystems and are one of the most widely distributed mammals on the
planet. In consequence, there has been significant interest in understanding their basic
biology and ecology. Long-term studies of Northern Hemisphere killer whales,
particularly in the eastern North Pacific (ENP), have identified three ecologically
distinct communities or ecotypes in that region. The success of these prominent ENP
studies has led to similar efforts at clarifying the role of killer whale ecology in other
regions, including Antarctica. In the Southern Hemisphere, killer whales present a
range of behavioural, social and morphological characteristics to biologists, who often
interpret this as evidence to categorize individuals or groups, and draw general ecological conclusions about these super-predators. Morphologically distinct forms
(Type A, B, C, and D) occur in the Southern Ocean and studies of these different
forms are often presented in conjunction with evidence for specialised ecology and
behaviours. Here we review current knowledge of killer whale ecology and ecotyping
globally and present a synthesis of existing knowledge. In particular, we highlight the
complexity of killer whale ecology in the Southern Hemisphere and examine this in
the context of comparatively well-studied Northern Hemisphere populations. We
suggest that assigning erroneous or prefatory ecotypic status in the Southern
Hemisphere could be detrimental to subsequent killer whale studies, because
unsubstantiated characteristics may be assumed as a result of such classification. On
this basis, we also recommend that ecotypic status classification for Southern Ocean
killer whale morphotypes be reserved until more evidence-based ecological and
taxonomic data are obtained.
