Tursiops Truncatus Montagu Research Articles

The prefrontal cortex of the bottlenose dolphin (Tursiops truncatus Montagu, 1821): a tractography study and comparison with the human.

Cetaceans are well known for their remarkable cognitive abilities including self-recognition, sound imitation and decision making. In other mammals, the prefrontal cortex (PFC) takes a key role in such cognitive feats. In cetaceans, however, a PFC could up to now not be discerned based on its usual topography. Classical in vivo methods like tract tracing are legally not possible to perform in Cetacea, leaving diffusion-weighted imaging (DWI) as the most viable alternative. This is the first investigation focussed on the identification of the cetacean PFC homologue. In our study, we applied the constrained spherical deconvolution (CSD) algorithm on 3T DWI scans of three formalin-fixed brains of bottlenose dolphins (Tursiops truncatus) and compared the obtained results to human brains, using the same methodology. We first identified fibres related to the medio-dorsal thalamic nuclei (MD) and then seeded the obtained putative PFC in the dolphin as well as the known PFC in humans. Our results outlined the dolphin PFC in areas not previously studied, in the cranio-lateral, ectolateral and opercular gyri, and furthermore demonstrated a similar connectivity pattern between the human and dolphin PFC. The antero-lateral rotation of the PFC, like in other areas, might be the result of the telescoping process which occurred in these animals during evolution.

Characterising an interaction between coastal bottlenose dolphins (Tursiops truncatus) and the spot gillnet fishery in southeastern North Carolina, USA

The aim of this study was to characterise interactions between coastal bottlenose dolphins (Tursiops truncatus Montagu, 1821), and the autumn gillnet fishery in southeastern North Carolina, USA that targets spot (Leiostomus xanthurus). Beach based (conducted from April 1997 - January 1998) and aerial surveys (conducted from July 1998 - May 1999) were used to estimate the abundance of dolphins and gillnets in nearshore waters. Commercial spot landings records from Brunswick County, North Carolina were used as an index of prey abundance. Stranded bottlenose dolphins were evaluated using protocols developed to describe diagnostic evidence of human-induced fisheries mortality. During both survey periods, dolphin numbers, gillnet numbers and spot landings all peaked in October-November. Simultaneously, an increase in dolphin strandings bearing evidence of entanglement in gillnets (cuts, lacerations, or wrapping marks on their appendages) was observed. Four stranded dolphins were determined to have been killed in gillnets, and one dolphin was removed alive from a gillnet in October 1997. Six stranded dolphins were killed in gillnets in October and November 1998. Thus, 20-24% of the annual allowable human-induced mortality for all USA Atlantic coastal bottlenose dolphins could be attributed to monofilament gillnets targeting spot in October and November in southeastern North Carolina. Both recreational and commercial fishermen target spot in the autumn using gillnets and dolphin mortality may be attributable to both aspects of the fishery. Results of this study are cause for alarm because interactions between dolphins and coastal gillnets may be occurring at much larger spatial and temporal scales along the USA Atlantic coast. Understanding the relationships between the biological and anthropogenic variables leading to these interactions can facilitate conservative, pro-active, management ensuring that human-induced mortality is not negatively impacting populations of marine mammals, such as Atlantic coastal bottlenose dolphins.

Analysing 25 years of bottlenose dolphin (Tursiops truncatus) strandings along the Atlantic coast of the USA: do historic records support the coastal migratory stock hypothesis?

Between June 1987 and March 1988, bottlenose dolphins (Tursiops truncatus Montagu 1821) along the US Atlantic coast experienced an epizootic. Monthly interquartile ranges of strandings during the epizootic were used to propose the Coastal Migratory Stock (CMS) of bottlenose dolphins (Scott et al., 1988). To date, the hypothesised CMS remains poorly understood. The goal of this study was to use a 25-year database to compare stranding patterns during the epizootic to those before (1972-1986) and after (1989-1997) the event. These comparisons reveal that monthly interquartile ranges during the epizootic are dissimilar to those before and after the event. The frequency distribution of total monthly strandings during the epizootic is also significantly different from those observed outside the event. Seasonal stranding patterns from 1989-1997 suggest more complex movements of dolphins along the US Atlantic coast than those of a single group ranging seasonally from Florida to New Jersey. In winter, for example, when the current model for the CMS predicts dolphin distributions concentrated in central Florida, the highest number of strandings occurred in North Carolina. Thus, these comparative analyses suggest that the pattern observed during the epizootic was anomalous, and not representative of stranding distributions for any other time period of the study. During the 15 years before the epizootic, and the nine years following, there was no clear picture of ‘migration’ of mortality along the coast. This study demonstrates how long-term, systematic collection of strandings data can be useful in testing hypotheses regarding the complex stock structure of coastal bottlenose dolphins. This knowledge will greatly enhance the ability to conserve and manage these animals as they recover from historic (i.e. directed takes and epizootic) and current sources of mortality.

Seasonal abundance and distribution patterns of common bottlenose dolphins (Tursiops truncatus) near St. Joseph Bay, Florida, USA

Three unusual mortalities events involving bottlenose dolphins (Tursiops truncatus Montagu 1821) occurred along Florida’s northern Gulf of Mexico coast between 1999 and 2006. The causes of these events, in which over 300 bottlenose dolphins are known to have died, are still under investigation. The impact of these mortality events cannot be fully evaluated, because little prior information on bottlenose dolphin abundance and distribution patterns exist in this region. Thus, the goals of this study were to estimate seasonal abundance, develop site-fidelity indices, and describe distribution patterns of bottlenose dolphins in St. Joseph Bay, Gulf County, Florida, USA. This study site was chosen because it was impacted by all three unusual mortality events and was the geographic focus of the 2004 event. Mark-recapture photo-identification surveys were conducted across multiple seasons from February 2005 through July 2007. Site-fidelity indices were calculated for each identifiable dolphin based upon all photo-ID efforts undertaken in the area. Distribution patterns were investigated by short-term (12-94 days) radio-tracking of tagged individuals across seasons (April-July, n=9; July-October, n=15). Mark-recapture closed and robust abundance estimates, as well as site-fidelity indices suggest that St. Joseph Bay supports a resident community of 78-152 bottlenose dolphins. During spring and autumn, this region experiences an influx of dolphins, as demonstrated by closed and robust abundance estimates of 313-410 and 237-340, respectively. These results are supported by the distribution patterns of radio-tagged individuals. Individuals tagged in summer tended to stay within or near St. Joseph Bay, whereas two individuals tagged in spring ranged more than 40km from the study site. This study provides the first detailed examination of bottlenose dolphin abundance and distribution patterns for this region of the northern Gulf coast of Florida. These results suggest that unusual mortality events probably had, and will in the future have, seasonally variable effects on bottlenose dolphins in St. Joseph Bay. Future mortality events that occur during the summer and winter in St. Joseph Bay may predominantly affect resident individuals, while those that occur during the spring and autumn will probably affect both residents and seasonal visitors.

A comparative analysis of the karyotypes of three dolphins - Tursiops truncatus Montagu, 1821, Tursiops australis Charlton-Robb et al., 2011, and Grampus griseus Cuvier, 1812.

The aim of this study is to produce G-banded karyotypes of three dolphin species, Tursiops truncatus Montagu, 1821, Tursiops australisCharlton-Robb et al., 2011, and Grampus griseus Cuvier, 1812, and to determine if any differences between the species can be observed. Monolayer skin cultures were established and processed for chromosome study by trypsin banding. The results indicate that the three species here investigated have the same diploid number (2n = 44) and very similar gross chromosome morphology, however G-banding allows distinction between each species. Chromosome 1 in G. griseus is significantly different from the other 2 species, and chromosome 2 in T. australis is subtly different from the other 2 species. This result is of potential significance in taxonomic studies, and can provide an unequivocal answer in the assessment of suspected hybrids between these species.

Analysis of BAER tests of Tursiops truncatus Montagu in comparison of captive males to naval trained males in the open ocean

Analysis of BAER tests of <i>Tursiops truncatus Montagu</i> in comparison of captive males to naval trained males in the open ocean

Investigating Atlantic bottlenose dolphin mismatch negativity response to pure tone stimuli

Marine mammals rely heavily on acoustic cues to survive but are susceptible to hearing impairment due to anthropogenic noise. The quality of life and well-being of marine mammals under professional care is based on enrichment through training and communication conspecifics and zoo staff. Mismatch Negativity (MMN) is an electrophysiological exam that records synchronized firing of neurons from the auditory cortex and frontal lobe, allowing for assessment of echoic memory and sound differentiation capability. The objective of this study is to conduct MMN exams, with acoustic stimuli, on the Atlantic Bottlenose Dolphin (Tursiops truncatus Montagu) to study echoic memory and develop auditory cognition assessments for marine mammals in captivity. Three male Atlantic Bottlenose dolphins were tested in water at the Indianapolis Zoo. The oddball paradigm in this study included a frequency difference between two pure-tone stimuli (standard 2000 Hz, deviant 500 Hz). The results suggest that a similar MMN waveform morphology and latency (between 100 and 300 ms) are seen in dolphins when compared to humans. Average P1, N1, P2, and MMN values were determined for each dolphin. Developing MMN tests for animals under professional care will allow for application to marine mammals in natural habitats, which are exposed to high levels of anthropogenic noise.

A common bottlenose dolphin (Tursiops truncatus) prey handling technique for marine catfish (Ariidae) in the northern Gulf of Mexico.

Few accounts describe predator-prey interactions between common bottlenose dolphins (Tursiops truncatus Montagu 1821) and marine catfish (Ariopsis felis Linnaeus 1766, Bagre marinus Mitchill 1815). Over the course of 50,167 sightings of bottlenose dolphin groups in Mississippi Sound and along the Florida coast of the Gulf of Mexico, severed catfish heads were found floating and exhibiting movements at the surface in close proximity to 13 dolphin groups that demonstrated feeding behavior. These observations prompted a multi-disciplinary approach to study the predator-prey relationship between bottlenose dolphins and marine catfish. A review was conducted of bottlenose dolphin visual survey data and dorsal fin photographs from sightings where severed catfish heads were observed. Recovered severed catfish heads were preserved and studied, whole marine catfish were collected and examined, and stranding network pathology reports were reviewed for references to injuries related to fish spines. Photographic identification analysis confirms eight dolphins associated with severed catfish heads were present in three such sightings across an approximately 350 km expanse of coast between the Mississippi Sound and Saint Joseph Bay, FL. An examination of the severed catfish heads indicated interaction with dolphins, and fresh-caught whole hardhead catfish (A. felis) were examined to estimate the presumed total length of the catfish before decapitation. Thirty-eight instances of significant trauma or death in dolphins attributed to ingesting whole marine catfish were documented in stranding records collected from the southeastern United States of America. Bottlenose dolphins typically adhere to a ram-feeding strategy for prey capture followed by whole prey ingestion; however, marine catfish skull morphology may pose a consumption hazard due to rigid spines that can puncture and migrate through soft tissue, prompting a prey handling technique for certain dolphins, facilitating consumption of the posterior portion of the fish without the head.

Connectivity in the network macrostructure of Tursiops truncatus in the Pelagos Sanctuary (NW Mediterranean Sea): does landscape matter?

AbstractThe bottlenose dolphin (Tursiops truncatus Montagu, 1821) is a regularly observed species in the Mediterranean Sea, but its network organization has never been investigated on a large scale. We described the network macrostructure of the bottlenose dolphin (meta)population inhabiting the Pelagos Sanctuary (a wide protected area located in the north‐western portion of the Mediterranean basin) and we analysed its connectivity in relation to the landscape traits. We pooled effort and sighting data collected by 13 different research institutions operating within the Pelagos Sanctuary from 1994 to 2011 to examine the distribution of bottlenose dolphins in the Pelagos study area and then we applied a social network analysis, investigating the association patterns of the photo‐identified dolphins (806 individuals in 605 sightings). The bottlenose dolphin (meta)population inhabiting the Pelagos Sanctuary is clustered in discrete units whose borders coincide with habitat breakages. This complex structure seems to be shaped by the geo‐morphological and ecological features of the landscape, through a mechanism of local specialization of the resident dolphins. Five distinct clusters were identified in the (meta)population and two of them were solid enough to be further investigated and compared. Significant differences were found in the network parameters, suggesting a different social organization of the clusters, possibly as a consequence of the different local specialization.

Life-history trade-offs in a generalist digenean from cetaceans: the role of host specificity and environmental factors.

BackgroundAdults and larvae of generalist parasites are exposed to diverse hosts and local environmental conditions throughout their life cycles, thus local adaptation is expected to occur through phenotypic plasticity and/or natural selection. We investigated how the combined effect of cryptic host specificity and local selective pressures could shape reproductive traits of a putative generalist parasite in the oceanic realm.MethodsThe LSU rDNA, ITS2 and the mt-COI of individuals of the digenean Pholeter gastrophilus (Kossack, 1910) Odhner, 1914 (Heterophyidae Leiper, 1909) from oceanic striped dolphins, Stenella coeruleoalba Meyen, and coastal bottlenose dolphins, Tursiops truncatus Montagu, in the western Mediterranean were used to elucidate whether worms were conspecific. Infection parameters were compared between both dolphin species. General Linear Mixed Models were used to analyse the influence of host species on four reproductive traits of P. gastrophilus: body size, maturity stage (non-gravid/gravid), egg size, and number of eggs in utero. AIC values were used to rank competing models, and p-values to assess the effect of specific predictors.ResultsEvidence indicated that worms collected from both dolphin species were conspecific. All worms collected were gravid and infection parameters did not differ between dolphin species. However, body size and egg size of individuals of P. gastrophilus were significantly larger in striped dolphins. The number of eggs in utero did not significantly differ between dolphin species but, for a given body size, worms in bottlenose dolphins harboured more eggs. A trade-off between egg size and egg number was found in worms from both dolphin species, with a higher slope in striped dolphins.ConclusionsApparently, striped dolphin is a more suitable host for P. gastrophilus, but reproductive investment seems to be adapted to the habitat where the life-cycle develops. Worms from striped dolphins likely face the problem of finding intermediate hosts in the oceanic realm and apparently invest into offspring size to enhance the early survival of larvae and the potential to multiply asexually within the first intermediate host. The small-sized worms from bottlenose dolphins would be adapted to reproduce early because of higher adult mortality, generating smaller and numerous eggs in a coastal habitat where chances of transmission are presumably higher.

Comparison of local knowledge about the bottlenose dolphin (Tursiops truncatus Montagu, 1821) in the Southwest Atlantic Ocean: New research needed to develop conservation management strategies

The aim of this study was to compare the local knowledge of artisanal fishermen about interactions between the bottlenose dolphin (Tursiops truncatus) and fisheries in Brazil and Uruguay. Between 2008 and 2011, we performed 88 interviews in Brazil (N = 66) and Uruguay (N = 22). Fuzzy logic was used to identify fishermen who could recognize the bottlenose dolphin. Seventy-nine fishermen (89.8%) identified the bottlenose dolphin, with 40 (50.6%) describing positive interactions, and 21 (34.4%) reporting negative interactions. In Brazil, the local ecological knowledge about the bottlenose dolphin was considered partial but more elaborate, as such knowledge was still incipient in Uruguay. Decreasing the impact of artisanal fishing on coastal populations of bottlenose dolphins in the southwest Atlantic Ocean (SAO) will require the regular monitoring of their areas of use and the locations where gillnets are arranged; consideration the size of the dolphins' populations and the fishing effort in each region; and the participation of social actors through educational activities, particularly in Brazilian areas, and the participation of social actors through educational activities (particularly in Brazilian areas, where the fishermen evinced feelings of competition in relation to the bottlenose dolphin) and improvements in the living and income conditions of these communities. From these results we propose measures for reducing anthropic impacts on bottlenose dolphin populations, including monitoring areas of use and the locations of fishing along the SAO as well as integrated management between social actors – government – research institutes for decisions about fishery management.

‘Human-dolphin ( Tursiops truncatus Montagu, 1821) cooperative fishery’ and its influence on cast net fishing activities in Barra de Imbé/Tramandaí, Southern Brazil

‘Human-dolphin ( Tursiops truncatus Montagu, 1821) cooperative fishery’ and its influence on cast net fishing activities in Barra de Imbé/Tramandaí, Southern Brazil – aims to describe ‘fishing with dolphins’ or ‘ botos’ ( Tursiops truncatus Montagu, 1821), its importance in mullet fishing in conjunction with the traditional knowledge of artisanal fishermen, and the negative economic impact that tourism has had on mullet fishing in Barra de Imbé/Tramandaí (29°58′S 50°07′W). In November and December of 2009, 22 artisanal fishermen associated with the Tramandaí Fishermen’s Union were interviewed. During these interviews, questionnaires were employed utilizing both open and closed questions that dealt with behavioral ecology, biological and interactional issues related to bottlenose dolphins, and small-scale fishing in the region. All those interviewed described “ boto fishing,” in which bottlenose dolphins “helped out the fishermen.” According to these interviews, this kind of fishing, marked by close interaction between humans and ‘ botos,’ allows nets to be cast fewer times and with captured fish yields that are greater than, when there is no dolphin is present. The fishermen maintain that this increased productivity results from ‘ botos’ showing them exactly where the schools of fish are located below the water surface. This has made it possible to observe the impact that dolphin fishing has on the monthly incomes of these fishermen, and there is concern among fishermen, that the intense tourism may one day contribute to the disappearance of the ‘ boto,’ a situation, they believe would negatively affect their fishing activities.

Investigation of the potential for vascular bubble formation in a repetitively diving dolphin

The production of venous gas emboli (VGE) resulting from altered dive behavior is postulated as contributing to the stranding of beaked whales exposed to mid-frequency active sonar. To test whether nitrogen gas uptake during repetitive breath-hold diving is sufficient for asymptomatic VGE formation in odontocetes, a bottlenose dolphin (Tursiops truncatus Montagu) was trained to perform 10-12 serial dives with 60 s surface intervals to depths of 30, 50, 70 or 100 m. The dolphin remained at the bottom depth for 90 s on each dive. Doppler and/or two-dimensional imaging ultrasound did not detect VGE in the portal and brachiocephalic veins following a dive series. Van Slyke analyses of serial, post-dive blood samples drawn from the fluke yielded blood nitrogen partial pressure (P(N(2))) values that were negligibly different from control samples. Mean heart rate (HR; +/-1 s.d.) recorded during diving was 50+/-3 beats min(-1) and was not significantly different between the 50, 70 and 100 m dive sessions. The absence of VGE and elevated blood P(N(2)) during post-dive periods do not support the hypothesis that N(2) supersaturation during repetitive dives contributes to VGE formation in the dolphin. The diving HR pattern and the presumed rapid N(2) washout during the surface-interval tachycardia probably minimized N(2) accumulation in the blood during dive sessions.

CETACEANS IN IRISH WATERS: A REVIEW OF RECENT RESEARCH

CETACEANS IN IRISH WATERS: A REVIEW OF RECENT RESEARCH

Lobomycosis as a disease of the Atlantic bottle-nosed dolphin (Tursiops truncatus Montagu, 1821).

Skin lesions on an Atlantic bottlenosed dolphin, captured off the coast of Florida, were investigated and found to be histologically and microbiologically indistinguishable from those caused in humans by Loboa loboi. All attempts to isolate the etiologic agent or to transmit the infection to mice and monkeys ended in failure. Sight records of other suspected dolphin cases of lobomycosis in Florida waters are described along with citations of two previously confirmed and published dolphin infections.

Distress Call of the Bottlenose Dolphin: Stimuli and Evoked Behavioral Responses

Analysis of the many different vocal productions of pairs of bottlenose dolphins (Tursiops truncatus Montagu) and the related behavior patterns shows that one pair of specific short (0.2 to 0.6 second) whistles was consistently stimulated by physical distress. This call stimulated nearby animals to push the head of the distressed animal to the surface to breathe. After the animal breathed, a vocal exchange preceded other forms of aid.

Records of Lancashire Cetacea

As records of Lancashire cetaceans are few, I thought it worth recording that when told of a 'big porpoise' washed up on the west Lancashire coast at Birkdale, Southport, on September 23, 1942, I identified it as a young male bottle-nosed dolphin (Tursiops truncatus Montagu) and took the following measurements: length 105 in., flippers 14 in., tail flukes 21 in. across, girth of body 50 in., depth of body 22 in., 'bottle nose' extension of upper jaw 5 in., 22 pairs of teeth in upper jaw, and probably same in lower but a few were removed by souvenirhunters. Upper parts black, also flippers ; underparts pale grey. The only previous Lancashire record I can trace was a specimen stranded at Walney Island on August 8, 19171.