scholarly journals Species information in whistle frequency modulation patterns of common dolphins

2021 ◽  
Vol 376 (1836) ◽  
pp. 20210046
Author(s):  
Julie N. Oswald ◽  
Sam F. Walmsley ◽  
Caroline Casey ◽  
Selene Fregosi ◽  
Brandon Southall ◽  
...  
Keyword(s):  
Communication Systems ◽  
Individual Recognition ◽  
Species Recognition ◽  
Vocal Learning ◽  
Single Species ◽  
Common Dolphin ◽  
Delphinus Delphis ◽  
Unsupervised Neural Network ◽  
Species Specific ◽  
Common Dolphins

The most flexible communication systems are those of open-ended vocal learners that can acquire new signals throughout their lifetimes. While acoustic signals carry information in general voice features that affect all of an individual's vocalizations, vocal learners can also introduce novel call types to their repertoires. Delphinids are known for using such learned call types in individual recognition, but their role in other contexts is less clear. We investigated the whistles of two closely related, sympatric common dolphin species, Delphinus delphis and Delphinus bairdii , to evaluate species differences in whistle contours. Acoustic recordings of single-species groups were obtained from the Southern California Bight. We used an unsupervised neural network to categorize whistles and compared the resulting whistle types between species. Of the whistle types recorded in more than one encounter, 169 were shared between species and 60 were species-specific (32 D. delphis types, 28 D. bairdii types). Delphinus delphis used 15 whistle types with an oscillatory frequency contour while only one such type was found in D. bairdii . Given the role of vocal learning in delphinid vocalizations, we argue that these differences in whistle production are probably culturally driven and could help facilitate species recognition between Delphinus species. This article is part of the theme issue ‘Vocal learning in animals and humans’.

scholarly journals First records of the pantropical spotted dolphin Stenella attenuata, within groups of common dolphins Delphinus delphis in northern Peru

2021 ◽  
Vol 56 (1) ◽  
pp. 78
Author(s):  
Lara Martínez ◽  
Sebastián Silva ◽  
Belén Alcorta ◽  
Aldo S. Pacheco
Keyword(s):  
Single Species ◽  
Northern Coast ◽  
Common Dolphin ◽  
Mixed Species ◽  
Delphinus Delphis ◽  
Spotted Dolphin ◽  
Northern Peru ◽  
Species Groups ◽  
Stenella Attenuata ◽  
Common Dolphins

Although dolphins are mostly known to form single species groups of varying size, occasionally they aggregate in mixed-species groups. The presence of mixed-species delphinid groups along the Peruvian coast is unknown. Herein, we report the presence of a single pantropical spotted dolphin (Stenella attenuata) within large groups of the common dolphin (Delphinus delphis) at Los Organos in the northern coast of Peru. Sightings occurred on October 10th, 2016, January 7th, 2018 and September 21st, 2019. In one sighting the mixed group was feeding, while during the other two sightings the group was travelling. These records add new evidence about mixed-species delphinid groups in coastal waters of Peru. 

scholarly journals Cetaceans using the marine protected area of "Parque Estadual Marinho da Laje de Santos", Southeastern Brazil

2017 ◽  
Vol 65 (4) ◽  
pp. 605-613 ◽  
Author(s):  
Marcos Cesar de Oliveira Santos ◽  
Giovanna Corrêa e Figueiredo ◽  
Marie-Francoise Van Bressem
Keyword(s):  
Protected Area ◽  
Marine Protected Area ◽  
Unknown Origin ◽  
Mantel Test ◽  
Southeastern Brazil ◽  
Common Dolphin ◽  
Balaenoptera Acutorostrata ◽  
Stenella Frontalis ◽  
Delphinus Delphis ◽  
Common Dolphins

Abstract The aim of this study was to evaluate the presence of cetaceans in the waters surrounding the Marine Protected Area (MPA) known as “Parque Estadual Marinho da Laje de Santos (PEMLS)”, placed in coastal waters at the southeastern coast of Brazil. Boat-based surveys were conducted once a month from June 2013 to June 2015. A specific transect was followed to cover the area of the quoted MPA, as well as its borders. A total of 24 boat-surveys rendered 18 sightings of cetacean groups of the following species: Atlantic spotted dolphin (Stenella frontalis) (12), rough-toothed dolphin (Steno bredanensis) (2), common dolphin (Delphinus delphis) (1), Bryde’s whale (Balaenoptera edeni) (2) and common minke whale (Balaenoptera acutorostrata) (1). Sightings of S. frontalis, the commonest sighted species, was positively correlated with water depth (Mantel test; r = 0.8072; p < 0.05). Photoidentified individuals moved back and forth to inner and outer areas of the MPA, remaining in the area throughout the 2-year survey. “Paisley” cutaneous marks of unknown origin were reported in two common dolphins for the first time in local waters. As the PEMLS has been used as an important spot for SCUBA divers, it is recommended that cetacean sightings could still be gathered in a future partnership, as well as using the acoustics tool to detect their presence when researchers are not in the field.

scholarly journals Short-term effects of tourism on the behaviour of common dolphins (Delphinus delphis) in the Azores

2017 ◽  
Vol 98 (5) ◽  
pp. 1187-1196 ◽  
Author(s):  
Arianna Cecchetti ◽  
Karen A. Stockin ◽  
Jonathan Gordon ◽  
José M.N. Azevedo
Keyword(s):  
Transition Probabilities ◽  
High Energy ◽  
Tourism Industry ◽  
Common Dolphin ◽  
Short Term ◽  
Delphinus Delphis ◽  
Critical Activity ◽  
Time Required ◽  
Common Dolphins

Short-term measures of behavioural responses of cetaceans to tourism operations have been used in many studies to interpret and understand potential long-term impacts of biological importance. The short-beaked common dolphin (Delphinus delphis) is the species most frequently observed in the Azores and constitutes an important component of the marine mammal tourism industry in this region. This study investigated the potential effects of tour boats on the behaviour of common dolphins off São Miguel, Azores, with particular focus on the changes in activity budget and the time required to resume activities after a tour boat interaction. Behavioural data were collected from land using a group focal-follow methodology. Markov chains were applied to analyse control and interaction sequences and to assess behavioural transition probabilities in both scenarios. In the presence of tour boats, dolphins significantly reduced the time spent foraging and increased the time engaged in other high energy activities. Dolphins also took significantly longer to resume feeding after an interaction occurred. The average bout length varied significantly between control and interaction scenarios, with foraging bouts being shorter during tour boats interactions. The results presented have management implications since feeding is a biologically critical activity. Disruption of foraging behaviour could lead to a decrease in energy intake for this population. With cetacean tourism likely to increase in the future, a precautionary approach to issuing new licences is advisable and any expansion would warrant an appropriate monitoring programme.

Acoustic Assessment of Populations of Common Dolphin Delphinus Delphis In Conjunction With Seismic Surveying

1996 ◽  
Vol 76 (3) ◽  
pp. 811-820 ◽  
Author(s):  
John C. Goold
Keyword(s):  
Seismic Survey ◽  
Avoidance Reaction ◽  
Common Dolphin ◽  
Survey Area ◽  
Delphinus Delphis ◽  
Air Gun ◽  
Before And After ◽  
Seismic Surveying ◽  
Acoustic Contact ◽  
Common Dolphins

Common dolphin, Delphinus delphis (bairdi), were monitored acoustically across a survey area of 2747 km2 during a three month period before, during and after an oil industry two dimensional (2D) seismic reflection survey. Over 900 h of audio survey data were collected and analysed, along with GPS positional data, to reveal trends in presence and distribution of animals. The presence of dolphins was determined from vocalization events on the survey recordings. Dolphin presence was assessed by a system of percentage acoustic contact. This was highest before and after the seismic survey, with common dolphins showing a clear south-westerly skew within the survey area and a probable south-westerly migration of animals between September and December. Acoustic contact with dolphins during the seismic survey also showed a south-westerly skew within the survey area, although percentages were lower. Monitoring during the period of seismic activity was restricted to the immediate vicinity (1–2 km) of the seismic vessel, so percentage contact most likely reflects the response of dolphins to such immediate activity. The overall result suggests an avoidance reaction by common dolphins to air gun emissions, although certain observations suggest tolerance to these sounds outside a 1 km radius of the guns.

scholarly journals Quantification of interactions between the Portuguese sardine purse-seine fishery and cetaceans

2015 ◽  
Vol 72 (8) ◽  
pp. 2438-2449 ◽  
Author(s):  
Ana Marçalo ◽  
Isidora Katara ◽  
Diana Feijó ◽  
Helder Araújo ◽  
Isabel Oliveira ◽  
...  
Keyword(s):  
Total Mortality ◽  
Purse Seine ◽  
Annual Number ◽  
Common Dolphin ◽  
The South ◽  
Delphinus Delphis ◽  
The North ◽  
Common Dolphins ◽  
Purse Seine Fishery ◽  
Purse Seining

Abstract Interactions between cetaceans and the purse-seine fishery operating along the whole Portuguese continental coast were studied based on on-board observations from 2010 to 2011. Cetacean presence and mortality were estimated and characteristics under which interactions were most likely to occur were identified. Observations were made on 163 fishing trips (0.7% of the average annual number of fishing trips) and 302 fishing operations/hauls. Cetaceans were present during 16.9% of fishing events; common dolphins (Delphinus delphis) accounted for 96% of occurrences, mostly overnight in summer and early autumn. Regression models showed that cetacean presence during a fishing set was significantly (p &lt; 0.05) associated with sardine catches, effort, and latitude/longitude. Encirclement and mortality occurred in 2.3 and 1.0% of fishing events, respectively. Encircled species were the common dolphin, bottlenose dolphin (Tursiops truncatus), and harbour porpoise (Phocoena phocoena), but only common dolphin showed mortality (three individuals); raised to fleet level, estimated total mortality rates of common dolphins were 69 (95% CI 37–110) in the north and 91 (95% CI 55–165) in the south for 2010 and 78 (95% CI 47–140) in the south only for 2011. The estimated annual mortality rate due to purse seining is 113 (95% CI 3–264) common dolphins, which is ∼0.63% of the current most optimistic estimate of population size for the Portuguese fishing area (SCANS II). The wide confidence limits, as well as variation between years, reflect low observer coverage, emphasizing the need for increased monitoring to cover gaps in the spatial and seasonal distribution of observer effort and provide reliable estimates of bycatch.

Behaviour of free-ranging short-beaked common dolphins (Delphinus delphis) in Gulf St Vincent, South Australia

2013 ◽  
Vol 61 (4) ◽  
pp. 291 ◽  
Author(s):  
Nicole E. Filby ◽  
Mike Bossley ◽  
Karen A. Stockin
Keyword(s):  
Group Size ◽  
Water Depth ◽  
Large Scale ◽  
South Australia ◽  
Population Level ◽  
Common Dolphin ◽  
Time Data ◽  
Fishing Activity ◽  
Delphinus Delphis ◽  
Common Dolphins

Common dolphins are subject to large-scale fishing activity and tourism operations in South Australia; however, there is a paucity of data on this species. Understanding the behaviour of a population can contribute greatly to our knowledge of a species and how to manage potential population-level threats. This paper describes the behaviour of short-beaked common dolphins (Delphinus delphis) in Australian waters for the first time. Data were collected from 109 independent dolphin groups during boat-based surveys conducted in Gulf St Vincent, South Australia, between September 2005 and May 2008. Activity budgets were used to assess behaviour of common dolphins in relation to diel patterns, season, water depth, sea surface temperature (SST), group size and composition. Foraging (33.9%) and resting (2.8%) were the most and least frequently observed behaviours, respectively. Travelling (33.0%), socialising (20.2%) and milling (10.1%) accounted for the remainder of the activity budget. Diurnal differences were detected, with foraging (59.5%) and socialising (31.8%) groups most frequently observed from 10.00 to 11.59 hours. Behaviour did not vary seasonally or with water depth, SST, group size or composition. Behaviour varied significantly between single- and multispecies aggregations. Foraging was more frequent in multispecies aggregations, as 78.4% of all foraging behaviour observed for common dolphins occurred in the presence of other species. Multispecies aggregations were most frequently observed with flesh-footed shearwaters (Puffinus carneipes), which were present during 29.4% of common dolphin encounters. Behaviour varied significantly during aggregations with shearwaters, as 62.2% of foraging groups occurred in the presence of shearwaters. Resting, milling or socialising was rarely observed in the presence of any other species, indicating that the primary mechanism for aggregations is likely prey-related.

Size data and stomach contents of common dolphins, Delphinus delphis, near Plymouth

1986 ◽  
Vol 66 (2) ◽  
pp. 319-322 ◽  
Author(s):  
P. L. Pascoe
Keyword(s):  
Natural History ◽  
Stomach Contents ◽  
British Museum ◽  
Common Dolphin ◽  
Delphinus Delphis ◽  
South West ◽  
Seasonal Basis ◽  
The Common ◽  
Common Dolphins ◽  
Size Data

INTRODUCTIONThe laboratory at Plymouth was notified of the capture of five dolphins in a commercial trawl on 9 December 1982, three of the specimens were living and therefore immediately released. The remaining two were brought to the laboratory, identified as Delphinus delphis Linnaeus, 1758, their size and sex were recorded and the stomachs removed for examination of their contents. The exact location of capture was not recorded, but is known to be within 40 miles of Plymouth.Reports of strandings of D. delphis collected by the British Museum (Natural History), (Harmer, 1914–27; Fraser, 1934, 1946, 1953, 1974) and more recent recorded sightings (Evans, 1980) show that the common dolphin is clearly not rare in British waters. Although the species has been recorded off all British coasts, sightings and strandings are concentrated off the south and south-west coasts of Britain and Ireland. The variation in their numbers and distribution both during this century and on a seasonal basis each year has been accounted for mainly by the fluctuation and movement of their food supply (Evans, 1980; Sheldrick, 1976).

scholarly journals Distribution and habitat modelling of common dolphins (Delphinus delphis) in the eastern North Atlantic

2019 ◽  
Vol 99 (06) ◽  
pp. 1443-1457 ◽  
Author(s):  
Ana M. Correia ◽  
Ágatha Gil ◽  
Raul Valente ◽  
Massimiliano Rosso ◽  
Graham J. Pierce ◽  
...  
Keyword(s):  
North Atlantic ◽  
Chlorophyll Concentration ◽  
Temporal Distribution ◽  
Distribution Patterns ◽  
Encounter Rate ◽  
Common Dolphin ◽  
North West ◽  
Delphinus Delphis ◽  
Eastern North Atlantic ◽  
Common Dolphins

AbstractThe eastern North Atlantic (ENA) has many highly productive areas where several species of cetaceans have been recorded, with the common dolphin (Delphinus delphis) being one of the most frequently sighted species. However, its spatial and temporal distribution in high seas is poorly known. The study presents the results from 5 years of cetacean monitoring in the ENA (2012–2016) aboard cargo ships that follow the routes from Continental Portugal to the Macaronesian archipelagos and north-west Africa. Common dolphin was the most frequently sighted cetacean with 192 occurrences registered on effort and an overall encounter rate of 0.36 sightings/100 nmi. The species was distributed in coastal and offshore waters, but absent from the Canaries and Cape Verde islands. Statistical ‘habitat’ models were developed to describe and explain the occurrence of sightings of the species: variables affecting detection of dolphins had a small impact and there were clear spatiotemporal distribution patterns, influenced to some degree by environmental variables. Predicted probability of occurrence was highest in coastal waters of continental Portugal and around the Azores. The models, combined with maps of distribution, were useful to identify important areas for the species, which could be the focus of future conservation efforts. Common dolphin presence was related to depth, distance to coast and seamounts, seabed slope, chlorophyll concentration, sea-surface temperature and sea level anomalies; the possible ecological significance of these relationships is explored.

scholarly journals Prey preferences of adult sea bass Dicentrarchus labrax in the northeastern Atlantic: implications for bycatch of common dolphin Delphinus delphis

2013 ◽  
Vol 70 (2) ◽  
pp. 452-461 ◽  
Author(s):  
J. Spitz ◽  
T. Chouvelon ◽  
M. Cardinaud ◽  
C. Kostecki ◽  
P. Lorance
Keyword(s):  
Dicentrarchus Labrax ◽  
Sea Bass ◽  
Common Dolphin ◽  
Bay Of Biscay ◽  
Predator Species ◽  
Delphinus Delphis ◽  
Prey Preferences ◽  
Common Dolphins ◽  
Trawl Fisheries ◽  
Northeastern Atlantic

Abstract Spitz, J., Chouvelon, T., Cardinaud, M., Kostecki, C., and Lorance, P. 2013. Prey preferences of adult sea bass Dicentrarchus labrax in the northeastern Atlantic: implications for bycatch of common dolphin Delphinus delphis – ICES Journal of Marine Science, 70: 452–461. In the northeastern Atlantic, adult sea bass (Dicentrarchus labrax) is one of largest fish living on the shelf, and this species has important commercial value. However, pelagic trawl fisheries that target sea bass have negative operational interactions with common dolphins (Delphinus delphis). Our goal was to determine the diet of adult sea bass in the Bay of Biscay from stomach-content and stable-isotope analyses, and explore the dietary overlap between sea bass and common dolphins. We found that sea bass primarily target small pelagic fish, most notably mackerel (Scomber scombrus), scads (Trachurus spp.), anchovy (Engraulis encrasicolus), and sardine (Sardina pilchardus). These four species also dominated the diets of common dolphins. This overlap in feeding preferences could increase the risk of dolphins being caught by trawl fisheries while feeding among sea bass, and may be an underlying mechanism to explain the high rate of common dolphin bycatch observed in the pelagic trawl fishery for sea bass in the Bay of Biscay. Understanding the foraging ecology and trophic interactions of predator species is an essential step for identifying and resolving management issues in the northeastern Atlantic and other marine ecosystems.

scholarly journals Atypical residency of short-beaked common dolphins ( Delphinus delphis ) to a shallow, urbanized embayment in south-eastern Australia

2016 ◽  
Vol 3 (9) ◽  
pp. 160478 ◽  
Author(s):  
Suzanne Mason ◽  
Chandra Salgado Kent ◽  
David Donnelly ◽  
Jeffrey Weir ◽  
Kerstin Bilgmann
Keyword(s):  
Common Dolphin ◽  
Small Community ◽  
Delphinus Delphis ◽  
Photo Identification ◽  
South Eastern ◽  
Eastern Australia ◽  
Face Threats ◽  
Common Dolphins ◽  
South Eastern Australia

Short-beaked common dolphins ( Delphinus delphis ) are typically considered highly mobile, offshore delphinids. This study assessed the residency of a small community of short-beaked common dolphins in the shallow, urbanized Port Phillip Bay, south-eastern Australia. The ability to identify common dolphins by their dorsal fin markings and coloration using photo-identification was also investigated. Systematic and non-systematic boat surveys were undertaken between 2007 and 2014. Results showed that 13 adult common dolphins and their offspring inhabit Port Phillip Bay, of which 10 adults exhibit residency to the bay. The majority of these adults are reproductively active females, suggesting that female philopatry may occur in the community. Systematic surveys conducted between 2012 and 2014 revealed that the dolphins were found in a median water depth of 16 m and median distance of 2.2 km from the coast. The shallow, urbanized habitat of this resident common dolphin community is atypical for this species. As a result, these common dolphins face threats usually associated with inshore bottlenose dolphin communities. We suggest that the Port Phillip Bay common dolphin community is considered and managed separate to those outside the embayment and offshore to ensure the community's long-term viability and residency in the bay.

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