Temporal–spatial distribution of an island‐based offshore population of common bottlenose dolphins (Tursiops truncatus) in the equatorial Atlantic

Abstract

A little‐studied common bottlenose dolphin (Tursiops truncatus) population inhabits the offshore waters surrounding Saint Paul's Rocks, a Brazilian marine protected area in the equatorial Atlantic Ocean. Five field expeditions (May 2011–May 2013) were conducted to characterize the habitat use, population size, and site fidelity of this population. Three different survey methods were employed: line‐transect surveys, land‐based surveys, and photo‐identification surveys. A population size of 23 individuals (19–28, CI 95%), which were present on most sampling days (>90% of surveys), was estimated. The maximum resighting interval of photo‐identified animals was 9 yr and 3 mo for five distinct individuals, based on data from nonsystematic efforts that have been ongoing since 2004. The dolphins exhibited strong site fidelity, as the minimum convex polygon (MCP, 95%) method revealed that they restricted their movements to a 0.5 km2 area across seasons and a 0.99 km2 area across years (95% kernel). The dolphins preferred shallow waters close to the archipelago (<1.2 km from the islands), especially on the eastern and southeastern sides, where oceanographic models have revealed persistent upwelling that may result from underwater currents and where food may be more predictably available.

Bottlenose dolphin ecotypes of the western South Atlantic: the puzzle of habitats, coloration patterns and dorsal fin shapes

“…Variations in the offshore ecotype color pattern, especially in small and isolated populations like that from Trindade Island, may arise for genetic or behavioral reasons. Small resident populations and low genetic variability are characteristics of the offshore bottlenose dolphins occupying the waters around the São Pedro and São Paulo Archipelago (Castilho et al 2015, Milmann et al 2017 and Trindade Island (see Carvalho & Rossi-Santos 2011).…”

“…In certain places, the distribution includes the coast, although it can also include the entire neritic zone, both on the continental slope and in oceanic waters. The offshore ecotype also occurs regularly near oceanic islands, such as the Trindade Archipelago (1200 km from the coast, Carvalho & Rossi-Santos 2011), São Pedro and São Paulo Archipelago (1010 km from the coast, Caon & Ott 2000, Milmann et al 2017, and Rocas Atoll (260 km from the coast, Baracho et al 2007). As our data have shown, groups of 17 to 25 offshore dolphins are common near the coast (<1 km).…”

Occurrence, residency patterns and habitat use of the bottlenose dolphin, Tursiops truncatus truncatus, on two Marine Protected Areas in Southeastern Brazil

“…Residency pattern studies in Brazil with T. truncatus truncatus are scarce (Milmann et al 2016, Lodi & Tardin 2018. However, for the T. truncatus gephyrus several studies report a high degree of residency in which dolphins present year-round occurrence, feeding and reproducing in these areas (e.g.…”

Distribución temporal de Stenella attenuata y Tursiops truncatus en La Libertad, El Salvador

“…La distribución espacial y temporal de los cetáceos está influenciada por una serie de variables ambientales, antrópicas, climatológicas (Cubero-Pardo, 2007;Griffin y Griffin, 2010;Martínez et al, 2011;Smith et al, 2016), también por resultado de migraciones a corta escala (Milmann et al, 2016). Así mismo, otros componentes que influyen son la presencia de especies depredadoras de mamíferos marinos de órdenes mayores y consumidores en el área y factores antrópicos, como las actividades de pesca y el tráfico marítimo, que generan colisiones con los delfines (Guzmán et al, 2012).…”