Abstract: Little is known about the biology of the Fraser’s dolphin (Lagenodelphis hosei), which is found in tropical and subtropical oceanic waters around the world. There is, depending on age and sex, great variation in intensity and development of the components of the colour pattern and external morphological characteristics of the species. The main characteristic of the colour pattern is the eye-toanus stripe, which has highly variable development. This is the first description of Fraser’s dolphin external appearance in the Southwestern Atlantic, based on 13 specimens stranded dead on the coast of Rio de Janeiro State (Brazil) around 22°30S. Individuals analysed presented sexual dimorphism in shape of the dorsal fin, presence of a post-anal hump and deepening of the caudal peduncle, features most prominent in mature males of the species. Specimens analyzed revealed that the Fraser’s dolphin possesses the same colour pattern and external morphological features reported in other areas.

Key Words: FRASER’S DOLPHIN; LAGENODELPHIS HOSEI; COLOUR PATTERN; EXTERNAL MORPHOLOGICAL FEATURES; SEXUAL DIMORPHISM; SOUTHWESTERN ATLANTIC; BRAZIL

Document Type: Research article