scholarly journals The bottlenose dolphin Tursiops truncatus foraging around a fish farm: Effects of prey abundance on dolphins’ behavior

2009 ◽  
Vol 55 (4) ◽  
pp. 243-248 ◽  
Author(s):  
Bruno Díaz López
Keyword(s):  
Group Size ◽  
Human Activities ◽  
Bottlenose Dolphin ◽  
Bottlenose Dolphins ◽  
Dive Duration ◽  
Fish Farm ◽  
Prey Abundance ◽  
Diving Behavior ◽  
Top Predators ◽  
Feeding Activities

Abstract The extent to which prey abundance influences both bottlenose dolphin foraging behavior and group size in the presence of human activities has not previously been studied. The primary aim of this study was to identify and quantify how wild bottlenose dolphins respond, individually and as groups, to the relative abundance of prey around a fish farm. Detailed views of dolphins’ behavior were obtained by focal following individual animals whilst simultaneously collecting surface and underwater behavioral data. A total of 2150 dive intervals were analyzed, corresponding to 342 focal samples, lasting over 34 hours. Bottlenose dolphins remained submerged for a mean duration of 46.4 seconds and a maximum of 249 seconds. This study provides the first quantified data on bottlenose dolphin diving behavior in a marine fin-fish farm area. This study’s results indicate that within a fish farm area used intensively by bottlenose dolphins for feeding, dolphins did not modify dive duration. Additionally, underwater observations confirmed that dolphins find it easier to exploit a concentrated food source and it appears that hunting tactic and not group size plays an important role during feeding activities. Thus, bottlenose dolphins appear capable of modifying their hunting tactics according to the abundance of prey. When top predators display behavioral responses to activities not directed at them, the task of studying all possible effects of human activities can become even more challenging.

scholarly journals On the behaviour of an under-studied population of bottlenose dolphins in the Southern Adriatic Sea

2018 ◽  
Vol 99 (4) ◽  
pp. 1017-1023 ◽  
Author(s):  
Flavio Affinito ◽  
Cristobal Olaya Meza ◽  
Aylin Akkaya Bas ◽  
Deborah Brill ◽  
Guy Whittaker ◽  
...  
Keyword(s):  
Group Size ◽  
Bottlenose Dolphin ◽  
Adriatic Sea ◽  
Bottlenose Dolphins ◽  
Anthropogenic Pressure ◽  
Social Predictors ◽  
Dolphin Population ◽  
Autumn And Winter ◽  
Effective Conservation ◽  
Study Monitoring

AbstractPerhaps the world's best-known cetacean, the bottlenose dolphin shows considerable variation in behaviour between and within populations in relation to differences in natural and anthropogenic conditions. Drivers of behavioural variation need to be identified to understand the dynamics of wild dolphin populations. Little research has been published on the bottlenose dolphin population found in the Southern Adriatic Sea. Using a set of spatial, temporal and social predictors, we aimed to investigate what variables are related to the behaviour of an under-studied population of bottlenose dolphins along the coastline of Montenegro. We present the results of a year-long study monitoring the behaviour of bottlenose dolphins along coastal Montenegro. We considered the effect of topography, seasonality and group size. A large proportion of travelling (55%) small groups (mean 4, range 1–9) in shallow waters (<50 m) was observed. We showed that seasonality alone explained behaviour best, with surface-feeding and socializing-resting increasing in autumn and winter. Group size was found to be a result of behavioural choice. We suggest seasonal changes in environmental conditions and anthropogenic pressure may explain the recorded behavioural pattern. This research points to the necessity of increased collaboration in the region to help understand complex patterns in behaviour and habitat use of local dolphin populations if effective conservation measures are to be developed.

Influence of artisanal fisheries on the behaviour and social structure of Tursiops truncatus in the South-western Gulf of Mexico

2019 ◽  
Vol 99 (8) ◽  
pp. 1841-1849
Author(s):  
Nataly Morales-Rincon ◽  
Eduardo Morteo ◽  
Christian Alejandro Delfín-Alfonso
Keyword(s):  
Gulf Of Mexico ◽  
Group Size ◽  
Age Structure ◽  
Human Activities ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Vantage Point ◽  
Competitive Interactions ◽  
Artisanal Fisheries ◽  
Behavioural Plasticity

AbstractBehavioural plasticity in animals is tested whenever competitive interactions for space and/or food resources occur between wildlife and human activities. This study uses the concepts of operational and non-operational interactions between bottlenose dolphins (Tursiops truncatus) and artisanal fisheries in Alvarado, to search for differences in behaviour, age structure and group size. We conducted 20 surveys between 2015 and 2016, and recorded 64 groups by means of scan sampling from either a research boat or a fixed vantage point. Average dolphin group size was small (${\bar{\rm x}}$ = 3.2, SD = 2.2 individuals) and fewer individuals were commonly present when interaction with fisheries occurred. Operational interactions were defined within the first 30 m and occurred mainly with lone individuals (54% recorded from the lighthouse and 82% during surveys); this benchmark also accounted for higher frequencies in locomotion and feeding (χ2 = 83.10; df = 7; P < 0.001). We found a higher rate of new behavioural events for dolphin groups furthest from human activities, as well as a decrease in behaviours that imply greater body exposure as dolphins approach the fishing spots. Age structure and dolphin group size were not different during and in the absence of interaction with fisheries, but most interactions involved male dolphins. Behavioural variations in the dolphins' repertoire are likely a strategy to reduce the risk of injuries or death when interacting with human activities; these dolphins seem to have habituated to or at least tolerate fishing activities within the study area, possibly constituting a sex-biased pressure.

Bottlenose dolphin (Tursiops truncatus) presence and incidental capture in a marine fish farm on the north-eastern coast of Sardinia (Italy)

2007 ◽  
Vol 87 (1) ◽  
pp. 113-117 ◽  
Author(s):  
Bruno Díaz López ◽  
Julia Andrea Bernal Shirai
Keyword(s):  
Marine Fish ◽  
Bottlenose Dolphin ◽  
Bottlenose Dolphins ◽  
Fish Farm ◽  
Eastern Coast ◽  
Encounter Rate ◽  
Photo Identification ◽  
Incidental Capture ◽  
The North ◽  
North Eastern

On the north-eastern coast of Sardinia, from November 2004 to January 2006, the first attempt in the Mediterranean basin to obtain information on encounter rate, group size and incidental capture of bottlenose dolphins in a marine fish farm was assessed, combining direct observations from fish farm boats with photo-identification studies. During 15 months of research, 79 d (65.3% of the total monitored days) were spent in direct observation of 146 groups of bottlenose dolphins around the fish farm cages. There was a peak in bottlenose dolphin presence during winter. Photographs were taken in the fish farm area during 79 encounters on 61 different days (totalling 34 marked individuals). The regular occurrence of some dolphins suggests individual preferences for the fish farm area. The incidental bottlenose dolphin capture observed in large, loose predator nets (1 dolphin per month) is cause for concern, as it is questionable whether or not the bottlenose dolphins in the area can sustain incidental capture of this magnitude. The information gained from this study shows the necessity for further regulations to be established, both in the use of predator nets and management of marine fish farms.

Further evidence of a context-specific agonistic signal in bottlenose dolphins: the influence of consortships and group size on the pop vocalization

Behaviour ◽  
2015 ◽  
Vol 152 (14) ◽  
pp. 1979-2000 ◽  
Author(s):  
Nicole L. Vollmer ◽  
Lee-Ann C. Hayek ◽  
Michael R. Heithaus ◽  
Richard C. Connor
Keyword(s):  
Regression Analysis ◽  
Group Size ◽  
Bottlenose Dolphin ◽  
Bottlenose Dolphins ◽  
Low Frequency ◽  
Shark Bay ◽  
Average Group ◽  
Context Specific ◽  
Male Alliances ◽  
Average Group Size

Pops are a low-frequency, pulsed vocalization produced by Indo-Pacific bottlenose dolphins (Tursiopscf.aduncus) in Shark Bay, Western Australia and are often heard when male alliances are consorting or ‘herding’ a female. Previous research indicated that pops produced in this context are an agonistic ‘come-hither’ demand produced by males and directed at female consorts. Here we examine pop occurrence during focal follows on bottlenose dolphin alliances with and without female consorts present. Regression analysis was conducted to determine if pop numbers were higher in the presence of female consorts, and if variables including group size alone and the interaction between presence/absence of a consortship and group size, influenced pop production. While the presence or absence of a consortship significantly affected the number of pops, average group size had no significant effect on pop production. Our research provides further evidence that the pop vocalization plays an important role in consortships.

Bottlenose dolphins at the southern extreme of the south-western Atlantic: local population decline?

2011 ◽  
Vol 92 (8) ◽  
pp. 1843-1849 ◽  
Author(s):  
Mariano A. Coscarella ◽  
Silvana L. Dans ◽  
Mariana Degrati ◽  
Griselda V. Garaffo ◽  
Enrique A. Crespo
Keyword(s):  
Group Size ◽  
Bottlenose Dolphin ◽  
Bottlenose Dolphins ◽  
Local Population ◽  
Population Decline ◽  
San Jose ◽  
Western Atlantic ◽  
Right Whale ◽  
Dolphin Population ◽  
Monitoring Protocols

The management scheme of Marine Protected Areas (MPAs) includes monitoring protocols but such activities are not always carried out. This is the case for Golfo San José, a MPA in northern Patagonia, Argentina. It was created in 1975 for the protection of the southern right whale (Eubalaena australis) breeding grounds. Other components of the system, such as dolphin populations have received little attention. This study is the first attempt to estimate sighting rates, group size and overall abundance of a bottlenose dolphin (Tursiops truncatus) population in Golfo San José and adjacent areas after 30 years. An analysis of the seasonal sighting rates indicates that bottlenose dolphins were present in the study area throughout the year but a decline in group size and abundance and major shift in distribution was detected when compared with previous published reports. The settlement of the MPA failed to secure the persistence of the bottlenose dolphin population within its boundaries. Possible explanations for the detected decline are addressed including increased natural mortality, human induced mortality and disturbance, resources depletion and environmental shift.

Involution and Cystic Transformation of the Thymus in the Bottlenose Dolphin, Tursiops truncatus

1994 ◽  
Vol 31 (6) ◽  
pp. 648-653 ◽  
Author(s):  
D. F. Cowan
Keyword(s):  
Body Size ◽  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Squamous Epithelium ◽  
Gulf Coast ◽  
Bottlenose Dolphins ◽  
Adult Life ◽  
Lymphoid Cells ◽  
Texas Gulf Coast ◽  
Thymic Cysts

The thymus glands of 10 bottlenose dolphins, Tursiops truncatus, collected along the Texas Gulf coast were examined using standard histologic and immunocytochemical methods. The thymus gland of Tursiops persists into adult life, represented by medulla and progressively thinning cortex. A network of epithelial cells, including Hassal bodies, is demonstrable using polyclonal anti-cytokeratin antibody. The network condenses, with loss of lymphoid cells as involution progresses. Cysts arise within the condensed network. These cysts, found in eight of 10 animals, increase in number and size with increasing body size. Body size tends to reflect age. Thymic cysts typically have an irregular shape when small but tend to become spherical as they enlarge. Theey may be lined by squamous epithelium of variable thickness. Eventually, the cysts become macroscopic and filled with a colloidlike material and may largely replace the thymus, which may be identified by noncystic remnants adjacent to the cysts.

Comparison of odontocete populations of the Marquesas and Society Islands (French Polynesia)

2008 ◽  
Vol 89 (5) ◽  
pp. 931-941 ◽  
Author(s):  
Alexandre Gannier
Keyword(s):  
Relative Abundance ◽  
Bottlenose Dolphin ◽  
Bottlenose Dolphins ◽  
Sperm Whale ◽  
French Polynesia ◽  
Society Islands ◽  
Spotted Dolphin ◽  
Abundance Indices ◽  
Beaked Whales ◽  
Using Data

Small boat surveys were organized to study cetaceans of the Marquesas (9°S and 140°W) and the Society Islands (17°S and 150°W) in French Polynesia. Prospecting took place from 12–15 m sailboats, between 1996 and 2001 with systematic visual searching. Boats moved according to sea conditions, at a mean speed of 10 km/h. Effective effort of 4856 km in the Marquesas and 10,127 km in the Societies were logged. Relative abundance indices were processed for odontocetes using data obtained with Beaufort 4 or less. In the Marquesas, 153 on-effort sightings were obtained on 10 delphinids species including the spotted dolphin, spinner dolphin, bottlenose dolphin, melon-headed whale and rough-toothed dolphin. In the Societies, 153 sightings of 12 odontocetes included delphinids (spinner, rough-toothed and bottlenose dolphins, short-finned pilot and melon-headed whales, Fraser's dolphin, Risso's dolphin and pygmy killer whale) and two species of beaked whales, the sperm whale and dwarf sperm whale. Relative abundance indices were higher in the Marquesas than in the Societies both inshore (0.93 ind/km2 against 0.36 ind/km2) and offshore (0.28 ind/km2 against 0.14 ind/km2). Differences in remote-sensed primary production were equally important, the Marquesas waters featuring an annual average of 409 mgC.m−2 · day−1 and the Societies of only 171 mgC · m−2 · day−1. The presence of a narrow shelf around the Marquesas also accounted for differences in odontocete populations, in particular the delphinids.

scholarly journals Differences in the whistle characteristics and repertoire of Bottlenose and Spinner Dolphins

2004 ◽  
Vol 76 (2) ◽  
pp. 386-392 ◽  
Author(s):  
Carmen Bazúa-Durán
Keyword(s):  
Geographic Variation ◽  
Discriminant Function Analysis ◽  
Bottlenose Dolphin ◽  
Function Analysis ◽  
Bottlenose Dolphins ◽  
Constant Frequency ◽  
Spinner Dolphin ◽  
Time Parameters ◽  
Spinner Dolphins

Several methods have been used to compare the whistles produced by dolphins. The two methods used in this study are: (1) a classification of whistle contours in six categories (i.e. constant frequency, upsweep, downsweep, concave, convex, and sine) and (2) the extraction of frequency and time parameters from each whistle contour. Bottlenose Dolphin Tursiops truncatus whistles are described in the same way when comparing whistle contour distributions in each of the six categories and whistle frequency and time parameters using Discriminant Function Analysis. For Spinner Dolphin Stenella longirostris whistles, each method describes whistles differently. Several facts may explain these differences in describing dolphin whistles, such as a greater fluidity of Spinner Dolphin groups when compared to Bottlenose Dolphin groups, greater geographic variation in the whistles of Bottlenose Dolphins than in those of Spinner Dolphins, an average beginning frequency 16% lower than the average ending frequency in Spinner Dolphin whistles compared to a varied relationship for Bottlenose Dolphins, and stricter criteria used to define whistle contour categories in the study of Spinner Dolphin whistles than in the Bottlenose Dolphin whistle study.

Taxonomy and distribution of bottlenose dolphins (genus Tursiops) in Australian waters: an osteological clarification

2020 ◽  
Vol 98 (7) ◽  
pp. 461-479 ◽  
Author(s):  
M. Jedensjö ◽  
C.M. Kemper ◽  
M. Milella ◽  
E.P. Willems ◽  
M. Krützen
Keyword(s):  
Bottlenose Dolphin ◽  
Bottlenose Dolphins ◽  
Three Dimensional ◽  
Large Sample Size ◽  
Type Specimens ◽  
Tursiops Aduncus ◽  
Common Bottlenose Dolphin ◽  
Intermediate Size ◽  
The Common ◽  
Taxonomic Studies

Species relationships in the bottlenose dolphin (genus Tursiops Gervais, 1855) are controversial. We carried out a comprehensive osteological study of 264 skulls, including type specimens, and 90 postcranial skeletons of Tursiops spp. to address taxonomic uncertainties in Australia using two-dimensional (2D) measurements, and three-dimensional geometric morphometrics (3DGM), tooth and vertebral counts, and categorical data. Analyses provided support for the presence of two forms, aligned to the Indo-Pacific bottlenose dolphin (Tursiops aduncus (Ehrenberg, 1832)) and the common bottlenose dolphin (Tursiops truncatus (Montagu, 1821)), including type specimens. The Burrunan dolphin (Tursiops australis Charlton-Robb, Gershwin, Thompson, Austin, Owen and McKechnie, 2011) fell well within T. truncatus for both 2D and 3DGM methods. Thirteen Tursiops spp. specimens, no T. australis specimens, were of intermediate size (2D) and could not be assigned to either species. For 3DGM data, there was a strong allometric influence and few non-allometric differences between species. Length and width of the cranium and rostrum were important discriminating variables. Tursiops aduncus was smaller, had more teeth, fewer vertebrae, and more erosion on the pterygoids and frontals than T. truncatus. Overall cranium shape was round in T. aduncus and angular in T. truncatus. Skull length of T. aduncus was smaller in low than in high latitudes. This study highlights the importance of large sample size, multiple analytical methods, and extensive geographical coverage when undertaking taxonomic studies.

scholarly journals Development and Validation of Monoclonal and Polyclonal Antibodies for the Detection of Immunoglobulin G of Bottlenose Dolphins (Tursiops Truncatus)

2007 ◽  
Vol 19 (5) ◽  
pp. 465-470 ◽  
Author(s):  
Hendrik H. Nollens ◽  
Linda G. Green ◽  
Diane Duke ◽  
Michael T. Walsh ◽  
Beth Chittick ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Polyclonal Antibody ◽  
Immunoglobulin G ◽  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Enzyme Linked Immunosorbent Assay ◽  
Common Bottlenose Dolphin ◽  
Circulating Antibodies ◽  
The Common

Antibodies directed against species-specific immunoglobulin G (IgG) have a broad range of applications in serologic and immunologic research and in the development of clinical assays. Validated anti-IgG antibodies for marine mammal species are in short supply. The objective of this study was to produce and validate antibodies with specificity for IgG of the common bottlenose dolphin ( Tursiops truncatus). Bottlenose dolphin IgG was purified using protein G. Two mouse monoclonal antibodies and a rabbit polyclonal antibody were developed from mice and rabbits immunized with bottlenose dolphin IgG. The specificity of the monoclonal antibodies and the polyclonal antibody for bottlenose dolphin IgG was first verified by Western blot analysis and enzyme-linked immunosorbent assay (ELISA). For further validation, both monoclonal antibodies and the polyclonal antibody were incorporated in an indirect ELISA for the detection of the immune response of bottlenose dolphins to a vaccine antigen. Three bottlenose dolphins were immunized with a commercial Erysipelothrix rhusiopathiae vaccine, and serial blood samples were collected from all dolphins for measurement of levels of circulating antibodies. Seroconversion was observed in all 3 dolphins by use of both monoclonal antibodies and the polyclonal antibody. Circulating antibodies were detectable as early as 6 days after immunization in 1 dolphin. Peak antibody levels were detected 14 days after the immunization. The ability to detect seroconversion in all 3 immunized bottlenose dolphins firmly establishes the specificity of the monoclonal antibodies and the polyclonal antibody for IgG of the common bottlenose dolphin.

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