This study revises and updates information on bottlenose dolphin Tursiops truncatusstrandings and sightings in northeastern Brazil. A total of 72 strandings were recorded from 1992 to 2010, and 51 sightings were recorded from 1988 to 2010 along the states from Ceará to Bahia, including Fernando de Noronha and São Pedro and São Paulo archipelagos, Rocas Atoll and Abrolhos Bank. Most strandings were recorded in the states of Pernambuco, Bahia and Rio Grande do Norte. The number of reports was higher during summer, but no statistically significant difference was found between summer and other seasons. The majority of the stranded animals were adults (70.6%). Stranded calves were not observed. Total body length ranged from 138 to 321cm: 138 to 310cm for males; and 168 to 288cm for females. The average adult body length was 281cm (SD = 0.22). For stranding events where sex was determined (n = 29), a highly statistically significant difference was found between the number of males (n = 21) and females (n = 8). A total of six animals (8.3%) showed evidence of fisheries interactions such as net marks or removal of meat, blubber and eyes. Twenty-two sightings were recorded in the northeastern region, mostly in small islands and Rocas Atoll. This finding shows that the bottlenose dolphin is mainly an oceanic species in the region. More efforts are needed to improve our understanding of the populations and conservation status of bottlenose dolphins in this region.
The coloration pattern of the estuarine dolphin, Sotalia guianensis, does not display variations in its distribution and the colour grey, as its common name suggests, is predominant. On the coast of the state of Rio Grande do Norte a dolphin was sighted with atypical coloration in relation to animals from that region. After observing its morphological characteristics, it was verified that the animal was a white specimen of S. guianensis. Although photographic recordings were made, the reddish coloration of the eye cannot be confirmed, a characteristic that would identify the animal as an albino dolphin. Despite not being very frequent, cases of coloration anomalies such as albinism have been previously recorded in 20 species of cetaceans. However, there have been no cases recorded for the estuarine dolphin.
The first record of prey-transfer behaviour between adult and calf animals in Sotalia fluviatilis is recorded. Five clear episodes of prey-transfer from adult animals to calves were observed, occurring in north-eastern Brazil at Pipa's Beach. These results suggest that food-sharing is a naturally occurring behaviour in the marine tucuxi dolphin, and that it may act as both a food supply and as an opportunity to obtain information about the food that is eaten by other group members.
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