Feeding ecology of the estuarine dolphin (Sotalia guianensis) on the coast of Rio Grande do Norte, Brazil

Abstract

We analyzed the stomach contents of 40 estuarine dolphins, Sotalia guianensis (van Benédén 1864), beached on the coast of Rio Grande do Norte, Brazil, between February 2000 and February 2007. A total of 223 prey items were identified, including 18 species of teleosts and 5 species of cephalopods. The index of relative importance (IRI) showed that Larimus breviceps, Haemulon plumieri, Lutjanus synagris, Trichiurus lepturus, Mugil curema, and Diapterus rhombeus were the six most important species. The IRI showed that L. breviceps was the main prey for both adults and the young. H. plumieri was the most important for the males and T. lepturus for the females. Seven species of teleosts and two of cephalopods were recorded in the diet of estuarine dolphins for the first time in the country. Our results suggest that the estuarine dolphin can be a feeding specialist and that foraging activity occurs mainly in estuarine areas, where the animals can use passive listening to detect prey.

Diet and foraging opportunism of the Guiana dolphin (Sotalia guianensis) in the Abrolhos Bank, Brazil

“…and Macrodon sp. in the Abrolhos Bank (present study) and Micropogonias furnieri , Porichthys porossisimus or Haemulon plumieri elsewhere (Cremer et al, ; Di Beneditto & Ramos, ; Pansard et al, ). This strongly suggests that Guiana dolphins diet changes spatially in accordance with prey availability.…”

Electroreception in the Guiana dolphin (Sotalia guianensis)

“…The dolphin was trained to respond to electrical stimuli in the order of magnitude of those generated by small to medium-sized fish, its natural prey [20,21]. Using a go/no-go paradigm, we determined the dolphin's detection thresholds for short square wave stimuli in a custom-made set-up (figure 2).…”

“…In flounders, bioelectric fields of 1000 mV cm 21 have been reported [43]. In platypuses, as in other electroreceptive species, the passive electrosensory system is used for the detection of bioelectric fields of benthic prey [44].…”

“…The dolphin responded calmly, and generally with a delay of approximately 2 s after stimulus onset; involuntary head saccades, as described in the platypus [23], were not found. The dolphin's sensory threshold was determined at 4.6 mV cm 21 by interpolating the percentage of correct go responses to stimuli (or hit rate) at the last stimulus intensity above threshold and the hit rate at the first stimulus intensity below threshold (figure 4). In control tests with the plastic shell covering the vibrissal crypts, the dolphin did not react to high-intensity electric field stimuli (40 trials performed).…”

Avaliação do turismo de observação de botos-cinza na Reserva Faunística Costeira de Tibau do Sul (REFAUTS), Rio Grande do Norte, Brasil

“…Essa é provavelmente uma das razões que tornam o boto-cinza uma das principais espécies-alvo do TOC na costa do Brasil. Na Refauts, praia de Pipa, o boto-cinza pode ser observado diariamente e tem sido estudado há pelo menos 22 anos, incluindo, por exemplo, a investigação de seu padrão comportamental (ARAÚJO et al, 2001;LUNARDI;FERREIRA, 2013;NASCIMENTO et al, 2008;SPINELLI et al, 2002), de sua dieta (PANSARD et al, 2011) e dos efeitos do turismo de observação sobre o comportamento desses animais (ALBUQUERQUE; SOUTO, 2013;CARRERA et al, 2008;VALLE;MELO, 2006 Contudo, apesar de sua relevante importância ecológica e econômica, o boto-cinza encontra-se vulnerável à extinção, segundo o Ministério do Meio Ambiente (ver Portarias MMA n. 444/2014 e n. 445/2014). Assim, tendo em vista a importância do TOC para a Refauts e para a economia local, este estudo tem como objetivo avaliar o turismo de observação de botos-cinza a partir de embarcação, por meio da: (i) descrição das embarcações licenciadas para o turismo de observação de botos-cinza; (ii) avaliação da frequência de passeios para observação de botos-cinza na Refauts; (iii) avaliação da conformidade das embarcações quanto à Lei Municipal n. 349/2007, que dispõe sobre o número máximo de embarcações na zona de uso restrito da Refauts e (iv) avaliação da rentabilidade do TOC na Reserva.…”