Bottlenose dolphins (Tursiops truncatus, Montagu 1821) in central-northern coast of Rio de Janeiro State, Brazil: stranding patterns and insights into feeding habits

Abstract

The bottlenose dolphin (Tursiops truncatus) may be one of the best known dolphin species worldwide, principally due to its coastal distribution in many regions. However, few studies about ecology, biology and threats have been conducted on the Brazilian coast. The aim of the present work is to analyze the stranding pattern and stomach contents of bottlenose dolphins in the central-north coast of the Rio de Janeiro State, from Saquarema to São Francisco de Itabapoana (~300km of coast line). Forty nine stranding events were recorded through regular beach surveys from 1999 to 2012 and also through access to previous published studies conducted since 1984. The strandings were distributed throughout the study area, but there was a trend of occurrence in the extreme southern and northern regions. Nine specimens showed evidence of accidental mortality in fishing nets. The strandings were more frequently recorded during autumn and winter (χ2; p < 0.05). Male bottlenose dolphins stranded more often than females, showing significant differences in this relationship (χ2; p < 0.05). Most stranded dolphins were classified as adults (> 230cm of body length) (χ2; p < 0.05). The body length varied from 106 to 335cm. Four prey species were found in the stomach contents from the three specimens of bottlenose dolphin analyzed. The most representative prey species was the cutlassfish (Trichiurus lepturus). This study showed that bottlenose dolphins are frequently found dead along the Rio de Janeiro State where they feed mainly on coastal fish. Future studies need to be conducted to improve the knowledge on this poorly known cetacean in Brazil.

Report of the Working Group on the Distribution of Tursiops truncatus in the Southwest Atlantic Ocean

“…scientific literature; the scientific collection of the Mammalogy Sector of the National Museum, RJ; personal observations and reliable communications from scientists and the general public based on familiarity with this species), included 85 new records of bottlenose dolphins for RJ (71 sightings and 14 strandings). In another literature review, Moura et al (2016 in every month of the year, but most records were from the austral summer months (50.8%, n = 63).…”

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

“…Few stomach content studies of bottlenose dolphins have been conducted in south-eastern Brazil (e.g. Di Beneditto et al ., 2001; Santos et al ., 2002; Melo et al ., 2010; Moura et al ., 2016), with only 14 stomachs analysed so far. These samples suggested an ichthyophagous feeding strategy, but the small sample size does not allow us to reach further conclusions regarding the influence of prey preferences on movement patterns in the surveyed area.…”

“…Few stomach content studies of bottlenose dolphins have been conducted in southeastern Brazil (e.g. Di Beneditto et al, 2001;Santos et al, 2002;Melo et al, 2010;Moura et al, 2016), with only 14 stomachs analysed so far. These samples suggested an ichthyophagous feeding The values are separated by the sectors (north and south) and genders by sector (southern males and females, and northern males and females).…”

“…The presence of Tursiops truncatus in inshore environments of the southern Brazilian coast allowed the development of more studies on the species, which has been surveyed for at least two decades (see Simões-Lopes & Fabian, 1999; Fruet et al ., 2011; Daura-Jorge & Simões-Lopes, 2016; Fruet et al ., 2017). Available data on T. truncatus from lower latitudes of the SAO (≤28 o S) comes mainly from scattered stranding records (see Santos et al ., 2010; Meireles et al ., 2016; Moura et al ., 2016), and a few survey efforts devoted to assessing live individuals near shore (e.g. Lodi et al ., 2008; Lodi & Monteiro-Neto, 2012).…”

Foraging habits and levels of mercury in a resident population of bottlenose dolphins (Tursiops truncatus) in Bocas del Toro Archipelago, Caribbean Sea, Panama

“…Ford et al, 1998;Hooker et al, 2001;Das et al, 2003;Riccialdelli et al, 2010;Milmann et al, 2016). Dietary estimation indicates that coastal bottlenose dolphins prey on cephalopods and a variety of demersal and pelagic fish (Mead and Potter, 1990;Van Waerebeek et al, 1990;Blanco et al, 2001;Gannon and Waples, 2004;De Pierrepont et al, 2005;Spitz et al, 2006;Milmann et al, 2016;Moura et al, 2016).…”