Movements and habitat use of bottlenose dolphins,Tursiops truncatus, in south-eastern Brazil

Abstract

Bottlenose dolphins (Tursiops truncatus) have been surveyed for at least two decades on the southern Brazilian coast. However, little is known about their distribution and habitat use in lower latitudes of the South-western Atlantic Ocean. Aiming to study the movements and distribution of the species along the south-eastern Brazilian coast, we made a comparison of photo-identified individuals of the species catalogued in 21 cruises conducted between 2012 and 2015. Additionally, we performed stable isotope analyses of carbon and nitrogen in skin samples (N = 35) to provide some insights of dolphin habitat use and trophic ecology through comparisons among individuals of distinct surveyed sectors (northern and southern) and sex. A total of 177 individuals were identified. Re-sightings (N = 24) occurred at intervals from 82 to 979 days at distances from 7 to 179 km. No individual was sighted in both sectors, suggesting spatial segregation. Isotopic comparisons showed no significant differences in carbon and nitrogen signatures between distinct sectors. However, ecological divergences were found when we divided the samples by gender. Wider isotopic niches were found for the northern bottlenose dolphins vs the southern ones, which could be related to temporal and spatial variation in the availability of resources, as well as possible differences in the home ranges of males and females in each region. This study represents a preliminary evaluation of ecological aspects of bottlenose dolphins along the Brazilian south-eastern coast, however, long-term studies on the feeding ecology and habitat use of this species are important to further improve our knowledge.

Molecular Detection of Pathogenic Leptospira sp. in Cetaceans from the Brazilian Coast

“…Noteworthy observe that coast species are more probable to be infected than oceanic species (p-value = 0.03), and the coastal species S. guianensis and P. blainvillei presented as infected in this study. It should be noted that some species, such as T. truncatus and S. bredanensis, have both coastal and oceanic behaviors along the Brazilian coast [40,41]; therefore, despite the international classification as oceanic [42], regional characteristics must be considered, and the results could be even more expressive. The real meaning of this finding is still an object of speculation.…”

Interactions between Cetaceans (suborder Odontoceti) and Artisanal Fishing in Brazil: an ethnoecological approach

“…The bottlenose dolphin (Tursiops truncatus), common in Southern Brazil, is widely distributed in temperate and tropical waters and uses a broad range of habitats, such as bays, lagoons, estuaries, and river mouths (Tullio et al 2015;Laporta et al 2016;Paschoalini and Santos 2020). Its global conservation status is classified as "Least Concern (LC)" by the IUCN Red List (Wells et al 2019), yet it is considered "Endangered (EN)" nationally by the Lista Oficial da Fauna Brasileira Ameaçada de Extinção (MMA 2022) (Table 3).…”

Machine Learning and Image Processing Methods for Cetacean Photo Identification: A Systematic Review

“…These studies are very important to evaluate the risk of their extinction and in that regard we refer to the Indo-Pacific humpback dolphins (Sousa chinensis) [31], Guiana dolphin (Sotalia guianensis) [35], Australian humpback dolphin (Sousa sahulensis) [49], Southern right whale (Eubalaena australis) [60], common (Balaenoptera acutorostrata) and Antarctic (Balaenoptera bonaerensis) minke whales [24], Ringed seal (Pusa hispida) [30], as well as the cosmopolitan bottlenose dolphins (Tursiops truncatus) [29], [42], [44], [51], [55], [61]. Finally, social dynamics is mainly focused on behaviours with photo ID tools that can recognize groups of individuals and their social evolution over time [28], [33], [36], [45], [46], [54], [59], and it can be particularly helpful with gender recognition.…”

“…), and any combination of these attributes can be selected to sort the catalogue. FinBase helps analysts, during photo [26], [31], [33], [46], [48], [49], [53], [63] (*) [30] (**) - [25], [28], [29], [35], [42], [45], [59], [61], [ identification studies, sort the entire catalogue based on the similarity of each existing catalogue individuals' attributes to those of a newly sighted individual [51], [54], [55], [61]. This system, while created for a bottlenose dolphin research application, can be adapted to accommodate photo identification research on a variety of other species.…”

“…• DARWIN [64] is an open-source computer vision system designed to identify individual bottlenose dolphins (Tursiops truncatus), facilitating the comparison of the contour of the dorsal fin of an unknown individual with a catalogue of known dolphins. DARWIN works semiautomatedly and has been used in several studies with some species of cetaceans, not only bottlenose dolphins [25], [28], [29], [35], [42], [45], [59], [61].…”