Common dolphins Delphinus delphis in southern Australia: A morphometric study

Abstract

Examination of 211 Delphinus specimens from the coasts of Western Australia to New South Wales, including Tasmania, was conducted using 62 quantitative and 11 qualitative variables. After refining the dataset, multivariate analyses were performed on 130 cranially mature specimens using 21 cranial variables. MANOVA showed males to be slightly larger than females, but with substantial overlap, allowing analyses to combine genders. UPGMA Cluster Analysis and MDS Ordination showed three largely overlapping groups based on a size gradient. K-means analysis of these groups found no significant differences and confirmed a size gradient. Discriminant analysis of specimens grouped by geography and water depth showed a tendency for large skulls to be from coasts adjacent to deep water and small skulls from shallow water coasts. Cranial measurements were significant, postcranial measurements and features were not. Tooth counts were within the range for D. delphis for all specimens examined. This study confirms genetic evidence for a single continuously variable species (Delphinus delphis Linnaeus, 1758) in southern Australian waters. Compared with either D. delphis or D. capensis from the eastern North Pacific, the skulls of D. delphis in southern Australia were more variable for many characters.