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Summary
Morphological characteristics, estimated age, gender, reproductive status,stomach contents and cause of death have been determined for 11 Hectorís dolphins (Cephalorhynchus hectori hectori), one Mauiís dolphin (Cephalorhynchus hectori maui), four common dolphins (Delphinus delphis), and one bottlenose dolphin (Tursiops truncatus).
The common dolphins and one Hectorís dolphin were killed incidentally in commercial fishing operations. The remaining Hectorís dolphins and the Mauiís dolphin were retrieved either from set-nets (n = 1), or found beachcast along the west coast of the North Island (n = 1), west coast of the South Island (n = 7), or east coast of the South Island (n = 2). The beachcast carcasses ranged from freshly dead to skeletal remains.
The stomachs of five Hectorís dolphins had detectable remains consisting of fish, otoliths, and fish bones. Fish and squid were equally represented in the stomachs of the common dolphins.
Age was estimated by counting dentinal growth layer groups in stained sections of teeth. Two female Hectorís dolphins were too decomposed to determine reproductive status but the remaining two were immature. Of five male Hectorís dolphins, one was pubertal, three immature, and one was too decomposed for examination of gonads. The male Mauiís dolphin and the bottlenose dolphin were also immature.
Of the four common dolphins, two Hectorís dolphins, and the bottlenose dolphin known to have been net-entangled, all had lesions consistent with death from asphyxiation. Two of the nine beachcast Hectorís dolphins had lesions indicative of entanglement, two did not appear to have been entangled and parasitic pneumonia may have had a role in their death, one died from acute blunt trauma of unknown origin, and four were too decomposed to determine cause of death. The Mauiís dolphin died from complications associated with Aspergillus fumigatus infection of the lungs.