A Potential Morphotype of Common Dolphin (Delphinus spp.) on the Northeast Coast of Venezuela

Abstract: Records of the common dolphin on the northeast coast of Venezuela have been widely documented. The complex topography and bathymetry of this area and the enhanced productivity due to upwelling processes promote the occurrence of common dolphin populations. It has not been clear, however, whether the species involved is Delphinus delphis or D. capensis. The aim of this contribution is to review taxonomically Delphinus spp. from the northeast coast of the country through skull morphometric analysis. A sample of 30 skulls comprised of specimens collected in Nueva Esparta State (n = 28) and Sucre State (n = 2) in Venezuela were analyzed using the morphometric parameters rostrum length (RL) and zygomatic width (ZW), including the ratio of the measurements RL/ZW. Only skulls identified as mature individuals (n = 16) were included in the analysis. The data were compared with published records of South Atlantic dolphins from Brazil and West Africa. Rostral length showed significant differences within the Venezuelan sample (p < 0.05) and between the dolphins from Brazil and West Africa. Zygomatic width also showed clear differences (Venezuela to Brazil, p < 0.05; Venezuela to West Africa, p < 0.05). In contrast, no differences were found for the RL/ZW ratio (Venezuela to Brazil, p = 0.21; Venezuela to West Africa, p = 0.33). Observations in the study area during sightings of common dolphins noted small females with calves. These observations suggested the occurrence of a small morphotype of common dolphin on the northeast coast of Venezuela, a semi-closed basin. Habitat conditions in this kind of ecosystem could lead to morphologic differences between smaller coastal forms and larger off-shore forms, an effect that could be related to feeding ecology.


Document Type: Research article

DOI: 10.1578/AM.33.2.2007.229

Page Numbers: 229 – 234

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