Note on the group size and behavior of Guiana dolphins (Sotalia guianensis) (Cetacea: Delphinidae) in Marapanim Bay, Pará, Brazil

Emin-Lima, Renata; Moura, Leiliany Negrão de; Rodrigues, Angélica Lúcia Figueiredo; Silva, Maria Luisa

doi:10.5597/lajam00165

Cited by 6 publications

(2 citation statements)

References 10 publications

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“…In general, Guiana dolphin groups comprise fewer than 20 individuals (e.g. Araújo, Passavante & Souto, 2001; Edwards & Schnell, 2001; Torres & Beasley, 2003; García & Trujillo, 2004; Santos & Rosso, 2007; Emin‐Lima et al, 2010; Santos et al, 2010; Lunardi & Ferreira, 2014; Espinoza‐Rodríguez et al, 2019; Barrios‐Garrido, De Turris‐Morales & Espinoza‐Rodriguez, 2021; Ribeiro‐Campos et al, 2021), although in Sepetiba Bay, this species has been observed historically to occur in large aggregations of hundreds of animals. These are considered to be among the largest groups found anywhere within the distribution of the Guiana dolphin (Flach, Flach & Chiarello, 2008).…”

Section: Discussionmentioning

confidence: 99%

20 years of research on the Guiana dolphin population of Sepetiba Bay, southeastern Brazil: What has changed?

Maciel,

Maricato,

Marqui

et al. 2023

Aquatic Conservation

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Despite the importance of coastal habitats for the provision of many ecosystem services, these areas are currently among the most impacted by human activities. Impacts on coastal ecosystems may affect many key species, such as the Guiana dolphin, which inhabits Sepetiba Bay in south‐eastern Brazil, a highly degraded environment owing to a human‐induced rapid environmental change. In this context, this study investigates the potential changes in the local Guiana dolphin behaviour, group structure, bioacoustics, site fidelity and habitat use over the past 20 years. For this, a historical database (1998–2007) was compared with current data on the local dolphin population (2017–2019). Between 2017 and 2019, the Guiana dolphins form significantly smaller groups (W = 3262.5, P > 0.001), spend more time foraging (61 vs. 10% in the past), emit whistles at a considerably lower rate (decreasing by 85.2%), have reduced site fidelity and now use a larger area. As Sepetiba Bay has been severely impacted by human activities in the recent past, with profound consequences for much of its biodiversity, the observed changes in dolphin behaviour are probably a consequence of habitat degradation and, in particular, of reduced prey availability. These findings have important implications for the management and conservation of the Guiana dolphin population of Sepetiba Bay. To break this human‐induced rapid environmental change, it will be essential to minimize the spatio‐temporal overlap of anthropogenic impacts, to avoid cumulative impacts. To mitigate anthropogenic impacts on the Guiana dolphins of Sepetiba Bay, it will be important to direct the following actions: (i) the regulation and control of anthropogenic noise; (ii) reduction and control of the release of chemical contaminants and organic effluents; (iii) more effective controls on vessel traffic within the areas used preferentially by the Guiana dolphin; and (iv) the implementation of measures to avoid overfishing and bycatch.

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Section: Discussionmentioning

confidence: 99%

20 years of research on the Guiana dolphin population of Sepetiba Bay, southeastern Brazil: What has changed?

Maciel,

Maricato,

Marqui

et al. 2023

Aquatic Conservation

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“…Such positive impact of nursery behavior on enlarging group size has not only been reported for the IPHDs in the eastern Taiwan Strait (Dungan et al, 2016), and also for other dolphin species such as bottlenose dolphins (Tursiops spp.) (Gibson and Mann, 2008b), dusky dolphins (Lagenorhynchus obscurus Gray, 1828) (Degrati et al, 2019), and Guiana dolphins (Sotalia guianensis) (Azevedo et al, 2005;Santos and Rosso, 2007;Emin-Lima et al, 2010). This social strategy i.e., dolphin group became larger when calves were present, could bring a variety of added benefits such as enhanced calf-assistance, cooperative calf-caring, reduced maternal investments, and increased calf-protection (against predators or intraspecific aggression) (Mann et al, 2000;Gibson and Mann, 2008a;Kent et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

Intra-Population Variability in Group Size of Indo-Pacific Humpback Dolphins (Sousa chinensis)

et al. 2021

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Group size is a key social trait influencing population dynamics of group-living animals. The Indo-Pacific humpback dolphins (IPHDs), Sousa chinensis, a shallow water delphinid species, display a fission-fusion social system. Yet little is known about how social organization of this species vary with temporal scales and behavioral state. In this study, we sampled group size estimates from the world’s second largest population of humpback dolphins (Sousa spp.), which inhabit the eastern waters of Zhanjiang, China. IPHD group sizes changed seasonally and inter-annually, but not with tidal phases. Group sizes also changed with behavioral state of IPHD groups and with number of mother-calf pairs present. IPHDs formed larger groups in the autumn than in other seasons, which might be related to seasonal changes in food availability and reproductive cycle. Of the groups observed, we recorded the presence of mother-calf pair in 85 groups (i.e., nursery groups: 47 ones with one pair, 25 ones with two pairs, and others with three pairs). Notably, nursery groups were about 2–4 times larger than non-nursery groups. In addition, group sizes greatly increased with the number of mother-calf pairs. Living in relatively large groups, more protection, food, and resources might be available for IPHD mothers and calves, and such social strategy provide higher reproduction efficiency and survival success for this species. During our observations, feeding (45.5%) and traveling (25.2%) represented the majority of IPHD’s behavioral budget, while socializing (8.4%) and resting/milling (6.8%) were not frequently observed. Resting/milling groups were approximately 50% smaller than feeding, traveling, or socializing groups, while the latter three types had a similar mean group size. Large groups when IPHDs foraged, traveled, or socialized, might provide more added group benefits. For the first time, our findings clearly revealed intra-population variability in IPHD group sizes across different behavioral and temporal variables, and provided a better understanding of IPHDs’ adaptations to various biological processes and ecological constraints.

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Asociaciones Entre Aves Marinas Y Sotalia Guianensis en El Sur Del Golfo De Venezuela

Espinoza-Rodríguez¹,

Carrasquero²,

Turris-Morales³

et al. 2015

Caldasia

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Caldasia 37(2): 309-318. 2015 RESUMENLas asociaciones entre aves marinas y mamíferos marinos es un evento común en todos los mares y océanos del mundo. Muchos autores han denominado estas asociaciones como relaciones comensalistas, oportunistas o parasitarias, según el efecto que dicha interacción resulte sobre una o ambas especies relacionadas. Con la finalidad de describir la existencia de agrupaciones entre Sotalia guianensis y aves marinas en la porción sur del Golfo de Venezuela, desde junio 2011 a junio 2012 se realizaron observaciones en plataformas móviles de grupos de este cetáceo y aves marinas, utilizando el protocolo "group-follow" bajo la metodología de "Ad libitum sampling". Todos los avistamientos fueron georreferenciados, realizándose anotaciones de la ocurrencia o no-asociación con aves marinas, de igual forma, se registró la especie y el número de aves presentes al momento de la interacción. Se realizaron 721 avistamientos, de los cuales en 197 eventos se registró asociación entre aves marinas y Sotalia guianensis. Las especies de aves marinas residentes que presentaron mayor frecuencia en eventos de asociación con S. guianensis fueron: Fregata magnificens (49%; n=98), Phalacrocorax brasilianus (29,5%; n=59) y Pelecanus occidentalis (22,5%; n=45); siendo Thalasseus maxima (71%; n=142) la única especie migratoria. Durante las observaciones realizadas en el período de muestreo se notó la presencia de una especie de golondrina (Riparia riparia) en un solo evento de agrupación con Sotalia guianensis. Dichas asociaciones aves-delfines, sólo fueron observadas cuando notables congregaciones de peces fueron registrados, donde el o los grupos de delfines realizaban alguna actividad con grandes movimientos de agua, lo que pudiese permitir a las aves realizar un menor gasto energético en la ubicación y la captura de la presa.Palabras clave. Aves marinas, Sotalia guianensis, Canal de navegación, Golfo de Venezuela.

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Note on the group size and behavior of Guiana dolphins (Sotalia guianensis) (Cetacea: Delphinidae) in Marapanim Bay, Pará, Brazil

Cited by 6 publications

References 10 publications

20 years of research on the Guiana dolphin population of Sepetiba Bay, southeastern Brazil: What has changed?

20 years of research on the Guiana dolphin population of Sepetiba Bay, southeastern Brazil: What has changed?

Intra-Population Variability in Group Size of Indo-Pacific Humpback Dolphins (Sousa chinensis)

Asociaciones Entre Aves Marinas Y Sotalia Guianensis en El Sur Del Golfo De Venezuela

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