Colour patterns of the dwarf minke whale Balaenoptera acutorostrata sensu lato: description, cladistic analysis and taxonomic implications

Abstract

Colour patterns of the dwarf minke whale, the most complex of any baleen whale, are described and illustrated. While variability is sufficient to allow recognition of individual whales, distinct colour elements consistently occur, including a light grey rostral saddle, dark grey spinal field and ivory white ventral field. Three dark lateral fields (nape field, continuing ventrally as a throat patch; thorax field; peduncle field) alternate with light grey thorax and flank patches and ivory white peduncle and shoulder blazes, the last variably in-filled by a dark axillary patch. The flipper has a diagnostic white basal blaze and dark grey distal patch. White mandible and eye blazes occur primarily on the right side.

Cladistic analyses were run using 13 colour characters and 12 taxa (11 baleen whales, representing all families; outgroup: sperm whale Physeter). The relationships between baleen whale families were poorly reflected in the analysis and no monophyletic groups were extracted. However the analysis suggested that the common minke whale Balaenoptera acutorostrata and the dwarf minke whale are most closely related. The common minke , dwarf minke and Antarctic minke whale Balaenoptera bonaerensis were also united, as only those species shared a double caudal chevron and discrete light grey lateral patches (anterior thorax and posterior flank patch) separated by a dark thorax field. Light grey lateral pigment, blowhole streaks, ear stripes and a tendency for colour asymmetry characterised most species of Balaenoptera. Colour pattern and other available data support Rice’s (1998) recognition of the dwarf minke whale as an as yet un-named subspecies of Balaenoptera acutorostrata. Cetacea, Balaenopteridae, colouration, phylogeny, taxonomy.