Ranging patterns of bottlenose dolphins living in oceanic waters: implications for population structure

Silva, Mónica; Prieto, Rui; Magalhães, Sara; Seabra, Maria Inês; Santos, Ricardo S.; Hammond, Philip S.

doi:10.1007/s00227-008-1075-z

Cited by 75 publications

(106 citation statements)

References 41 publications

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“…Both species were observed year-round but encounter rates varied greatly between months. Photo-identification data showed that in addition to resident populations of both species, a few hundred non-resident dolphins are identified each year in the Azores (Silva et al 2008;Hartman et al 2009). Although we cannot rule out potential effects of variability in survey effort, temporary immigration of a large number of non-resident dolphins into the study area could help explaining fluctuations in the number of sightings per month.…”

Section: Discussionmentioning

confidence: 99%

Spatial and temporal distribution of cetaceans in the mid-Atlantic waters around the Azores

Silva

Prieto

Cascão

et al. 2013

Marine Biology Research

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116

158

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Cetaceans living in offshore waters are under increasing pressure from anthropogenic activities. Yet, due to the lack of survey effort, relatively little is known about the demography or ecology of these populations. Spatial and temporal distribution of cetaceans in mid-Atlantic waters were investigated using a long term dataset collected from boat surveys and land-based observations around the Azores. From 1999 to 2009, 7307 cetacean schools were sighted during 271717 km of survey effort. In 4944 h of land-based observations, 2968 cetacean groups were detected. Twenty-four species were recorded: seven baleen whales, six beaked whales, eight dolphin species, Physeter macrocephalus, Kogia breviceps and K. sima. Overall, Delphinus delphis was the most frequently sighted species but its encounter rate decreased in JuneNovember, coinciding with presence of Stenella frontalis in the region. Tursiops truncatus, P. macrocephalus and Grampus griseus were frequently encountered yearround, whereas large baleen whales showed a distinct peak in encounter rates in March-May. Mesoplodonts were fairly common and appear to be present throughout the year. These findings fill-in a significant gap in the knowledge of cetaceans occurring in a poorly studied region of the North Atlantic, providing much needed data to inform management initiatives.

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Section: Discussionmentioning

confidence: 99%

Spatial and temporal distribution of cetaceans in the mid-Atlantic waters around the Azores

Silva

Prieto

Cascão

et al. 2013

Marine Biology Research

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116

158

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“…Although the shortest recorded time frame between an animal being re-identified in both areas was 14 days, this should not be regarded as the minimum time, as subsequent re-identification is also effort dependent. The analysis of ranging patterns of dolphins is crucial to understand several aspects of the ecology of a population (Silva et al, 2009), as dispersion is a biologically important behaviour triggered by a range of key functions such as feeding, mating and finding shelter (e.g. Bearzi et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

“…Among coastal populations of bottlenose dolphins, males seem to have a wider home range than females, related to their mating strategy (Wells et al, 1987). Furthermore, female ranging patterns are considered to be minimal for reasons of energetic efficiency (Sandell, 1989) and are usually thought to be more directly affected by ecological parameters such as the availability of resources and predation risk (Silva et al, 2009). Accordingly, females associated with a calf were determined as being significantly more resident in BSA than individuals without calves (Vermeulen and Cammareri, 2009a;Vermeulen, 2011).…”

Section: Discussionmentioning

confidence: 99%

“…Despite the fact that this species is considered the most extensively studied dolphin species, information on movements and home ranges in the Southwest Atlantic Ocean are still scarce (see Laporta et al, 2016 Report of the Working Group on Habitat Use, this volume). However, insight into the movement patterns of these dolphins is vital to comprehend ecological aspects of the population (Silva et al, 2009), and will contribute towards the increasing conservation need in the country. obs.).…”

Section: Introductionmentioning

confidence: 99%

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Occurrence of bottlenose dolphins (Tursiops truncatus) in the Río Negro Estuary, Argentina, and their mid-distance movements along the northeastern Patagonian coast

Failla¹,

Seijas

Vermeulen

2017

Lat. Am. J. Aquat. Mamm.

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A systematic study was carried out on bottlenose dolphins (Tursiops truncatus) in the Río Negro Estuary (RNE), Patagonia, Argentina, to analyze their occurrence and activity patterns in this region. The photo-identification data of this study was further compared to data from an adjacent region to gain information on the animals' movements along the northeastern Patagonian coast. Information was gathered through land-based observations between the months of March and July of 2008 up to 2011. Data on dolphin activity patterns were collected via an ad libitum focal-group sampling mode. At the same time, dorsal fin images were obtained from as many dolphins as possible for identification and subsequent re-identification of individuals. Total effort equaled 188h, resulting in 58h of observation of 124 dolphin groups [sightings per unit effort (SPUE) = 0.66 group/h]. Most of the groups observed contained between one and five individuals, and two main activity states could be determined, namely traveling (65%) and foraging (26%). The photo-identification effort, which started opportunistically in 2006, resulted in a catalogue of 17 individual dolphins, with a total mean re-identification rate of nine days (max. = 24 days). When comparing these pictures to the existing catalogue of Bahía San Antonio (BSA; approximately 200km west from the study area) dorsal fins of 15 individuals could be matched and most (n = 12) could be subsequently re-identified in both areas, indicating their long distance movements along the northeastern Patagonian coast during the austral autumn months. This season coincides with the lowest dolphin abundance and feeding activity in BSA. This study indicates that bottlenose dolphins enter the RNE to forage at least during autumn. It further suggests that the search for food resources is the main trigger for their movement patterns along the northeastern Patagonian coast during this season, at least for certain individuals. More research is needed to accurately confirm these hypotheses.

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“…Residency has been shown to be associated with population differentiation in other species (e.g., bottlenose dolphins of the species T. aduncus in Australia, Möller and Beheregaray 2004; spinner dolphins in the South Pacific, Oremus et al 2007). However, in the Azores, no population differentiation was found in T. truncatus despite the existence of known resident individuals (Quérouil et al 2007;Silva et al 2008). The extent of differentiation might depend on the proportion of individuals that are resident.…”

Section: Absence Of Population Structure Within and Between Archipelagosmentioning

confidence: 95%

Molecular insight into the population structure of common and spotted dolphins inhabiting the pelagic waters of the Northeast Atlantic

Quérouil

Freitas²,

Cascão

et al. 2010

Mar Biol

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Molecular insight into the population structure of common and spotted dolphins inhabiting the pelagic waters of the Northeast Atlantic. Marine Biology, Springer Verlag, 2010, 157 (11), pp.2567-2580. <10.1007/s00227-010-1519-0>. 1 Molecular insight on the population structure of common and spotted dolphins inhabiting the pelagic waters of the Northeast Atlantic AbstractSeveral cetacean species exhibit fine-scale population structure despite their high dispersal capacities and the apparent continuity of the marine environment. In dolphins, most studies have focused on coastal areas and continental margins, and they revealed differentiated populations within relatively small geographic areas, sometimes in conjunction with a specialization for different habitats (ecotypes). We analysed the population genetic structure of short-beaked common dolphins (Delphinus delphis) and Atlantic spotted dolphins (Stenella frontalis) in the Azores and Madeira, the two most isolated archipelagos of the North Atlantic. The archipelago of the Azores is divided into three groups of islands and stands 900 km away from Madeira. It is not known whether individuals migrate between groups of islands and archipelagos, nor whether distinct ecotypes are present. These questions were investigated by genetic analyses of 343 biopsy samples collected on free-ranging dolphins. The analyses consisted in sequencing part of the mitochondrial hyper-variable region, screening up to 14 microsatellite loci, and molecular sexing. Results did not unravel any population structure at the scale of the study area. Lack of differentiation matches expectations for spotted dolphins, which are transient in both archipelagos, but not for common dolphins, which are present year-round in the Azores and potentially resident. Absence of genetic structure over hundreds and even thousands of kilometres implies the existence of gene flow over much larger distances than usually documented in small delphinids, which could be achieved through individual movements. This finding indicates that population structure in oceanic habitat differs from that observed in coastal habitat.

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Ranging patterns of bottlenose dolphins living in oceanic waters: implications for population structure

Cited by 75 publications

References 41 publications

Spatial and temporal distribution of cetaceans in the mid-Atlantic waters around the Azores

Spatial and temporal distribution of cetaceans in the mid-Atlantic waters around the Azores

Occurrence of bottlenose dolphins (Tursiops truncatus) in the Río Negro Estuary, Argentina, and their mid-distance movements along the northeastern Patagonian coast

Molecular insight into the population structure of common and spotted dolphins inhabiting the pelagic waters of the Northeast Atlantic

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