Tursiops Research Articles

Discrimination of double-click synthetic echoes by bottlenose dolphins: Effects of inter-highlight interval and phasea).

Two bottlenose dolphins (Tursiops truncatus) were trained to discriminate double-click synthetic "echoes" differing in inter-highlight interval (IHI). In the first experimental task, dolphins passively listened to background (S-) stimuli with constant IHI and responded on discriminating a change to target (S+) stimuli with a slightly increased IHI. The second task was similar, but the highlights were assigned random, frequency-independent phase angles. This phase randomization was designed to interfere with potential auditory cues from characteristic spectral interference patterns linked to IHI changes. Discrimination thresholds were higher with randomized phase when the S- stimuli had IHIs of 50-250 μs. Thresholds were highest and comparable at the longest S- IHIs of 375 and 500 μs and were independent of phase condition. Although dolphin detection of changes in highlight envelope timing can explain threshold patterns at 375 and 500 μs, this cue did not explain performance at IHIs less than the dolphin auditory temporal window of ∼250 μs. Modeling results suggested that phase manipulations eliminated the availability of a simple difference in spectral magnitudes at the shortest IHIs, but the perception of a time separation pitch cue may still explain the dolphins' observed threshold patterns.

POPULATION PHARMACOKINETICS OF CEFPODOXIME IN BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS).

Cefpodoxime proxetil is commonly used to treat cetacean patients with suspected or confirmed bacterial infections; however, pharmacokinetic data are needed to guide proper dosing in these species. Cefpodoxime proxetil is a time-dependent, semisynthetic, third-generation cephalosporin, appropriate for once-daily dosing and U.S. Food and Drug Administration-approved for use in dogs with a broad spectrum of activity including gram-positive and gram-negative species. The objective of this study was to evaluate the population pharmacokinetics of cefpodoxime in bottlenose dolphins (Tursiops truncatus). A sparse-sampling design was used, with serum from dolphins receiving cefpodoxime proxetil at 10 mg/kg orally every 24 h to treat suspected or confirmed bacterial infections. Serum samples (n = 57) from 24 dolphins were analyzed at 12 time points from 0 to 96 h postdose. Serum samples were analyzed using liquid chromatography-mass spectrometry. Population pharmacokinetic analysis was performed using nonlinear mixed-effects modeling. One- and two-compartment linear models with first order absorption were tested. Covariates including weight, age, and sex were considered for inclusion in the model, and between-subject variability was incorporated. A two-compartment model performed best, where following an oral dose of 10 mg/kg, serum concentration reached a mean maximum concentration of 23.0 µg/ml, mean time to maximum concentration of 5.0 h, and mean half-life of 11.4 h. With daily dosing, accumulation was approximately 18% and steady state was reached by the second dose. Serum protein binding was 82.8% as determined by equilibrium dialysis, similar to plasma protein binding reported in dogs. Based on the population pharmacokinetic model, once-daily oral dosing was systemically absorbed and quickly reached maximum concentrations. The half-life in dolphins appears to be longer than other species studied to date. Given the paucity of antimicrobial pharmacokinetic studies in dolphins, and limited once-daily oral antibiotic options for this species, these data are helpful for clinicians to make informed antimicrobial choices.

A review of lobomycosis and lobomycosis-like skin disease in cetaceans worldwide, with new data from the Gulf of Guayaquil, Ecuador.

Lobomycosis, also called paracoccidioidomycosis ceti, is a chronic mycotic cutaneous disease affecting odontocetes. Lobomycosis-like disease (LLD) has a clinical presentation consistent with lobomycosis but lacks a histological and molecular diagnosis. We review the literature on lobomycosis aetiology, clinical signs and pathogenesis, species affected and geographic distribution and examine the factors influencing the presence, transmission and prevalence of the disease, to better understand its ecology. In addition, we provide unpublished information on LLD in two common bottlenose dolphin (Tursiops truncatus) communities inhabiting the Gulf of Guayaquil, Ecuador. Lobomycosis and LLD occur in Delphinidae from the Atlantic, Pacific, and Indian Oceans between 33°N and 35°S. Primary risk factors include habitat, sex, age, sociality, and pollution. In dolphins from the Americas and Japan, lobomycosis is caused by Paracoccidioides ceti, family Ajellomycetaceae. The disease is characterized by cutaneous granulomatous lesions that may occur anywhere on the body, grow to large size, and may ulcerate. Histologically, the lesions consist of acanthosis and histiocytic granulomas between the skin and subcutaneous tissues, with inflammatory changes that extend deep into the dermis. Multiple yeast cells with a double refringent layer stained positive using Gomori-Grocott methenamine silver in the dermis of a T. truncatus from Ecuador diagnosed with LLD since 2011, a first record for the Southeast Pacific. Injuries may enable the entry of P. ceti into the dermis while skin contact likely favours transmission, putting males at higher risk than females. Lobomycosis and LLD may have a negative impact on small communities already threatened by anthropogenic factors.

An analysis of suspected microplastics in the muscle and gastrointestinal tissues of fish from Sarasota Bay, FL: exposure and implications for apex predators and seafood consumers.

Microplastics have been found in the gastrointestinal (GI) fluid of bottlenose dolphins (Tursiops truncatus), inhabiting Sarasota Bay, FL, suggesting exposure by ingestion, possibly via contaminated fish. To better understand the potential for trophic transfer, muscle and GI tissues from 11 species of dolphin prey fish collected from Sarasota Bay were screened for microplastics (particles <5 mm diameter). Suspected microplastics were found in 82% of muscle samples (n=89), and 97% of GI samples (n=86). Particle abundance and shapes varied by species (p<0.05) and foraging habit (omnivore vs. carnivore, p<0.05). Pinfish (Lagodon rhomboides) had the highest particle abundance for both tissue types (muscle: 0.38 particles/g; GI: 15.20 particles/g), which has implications for dolphins as they are a common prey item. Findings from this study support research demonstrating the ubiquity of estuarine plastic contamination and underscore the risks of ingestion exposure for wildlife and potentially seafood consumers.

Serological Investigation for Brucella ceti in Cetaceans from the Northwestern Mediterranean Sea.

Neurobrucellosis in cetaceans, caused by Brucella ceti, is a relevant cause of death in striped dolphins (Stenella coeruleoalba) from the Mediterranean Sea. Serological tests are not used as a routinary technique for the diagnosis of this infection. We briefly describe the pathological findings of nine free-ranging stranded cetaceans diagnosed with Brucella disease or infection in our veterinary necropsy service from 2012 to 2022. The findings included focal diskospondylitis and non-suppurative meningitis, choroiditis and radiculitis. Additionally, an exploratory serological study was conducted in sixty-six frozen sera collected in the period 2012-2022 from fifty-seven striped dolphins, five Risso's dolphins (Grampus griseus), two common bottlenose dolphins (Tursiops truncatus), one common dolphin (Delphinus delphis) and one pilot whale (Globicephala melas) to compare antibody levels in Brucella-infected (n = 8) and non-infected (n = 58) animals, classified by the cause of death, sex, age class and cetacean morbillivirus (CeMV) infection status. The authors hypothesized that active infection in cases of neurobrucellosis would elicit a stronger, detectable humoral response compared to subclinical infections. We performed a commercial competition ELISA (cELISA) using serial serum dilutions for each sample, considering a percentage of inhibition (PI) of ≥40% as positive. A titer of 1:160 was arbitrarily determined as the seropositivity threshold. Seropositive species included striped dolphins and Risso's dolphins. Seroprevalence was higher in animals with neurobrucellosis (87.5%) compared to the overall seroprevalence (31.8%) and to other causes of death, indicating, likely, a high sensitivity but low specificity for neurobrucellosis. Animals with chronic CeMV seemed to have higher seroprevalences, as well as juveniles, which also had a higher disease prevalence. These results indicate, as in other studies, that antibodies are not decisive against clinical brucellosis, although they may indicate a carrier state, and that CeMV may influence Brucella epidemiology. More research is required to elucidate the epidemiology and pathogenesis and to resolve the complicated host-pathogen interaction in Brucella species.

Dynamics of multilevel alliances in St. Johns River, Florida, Tamanend's bottlenose dolphins (Tursiops erebennus) with respect to an epizootic unusual mortality event

AbstractDisturbance events can alter a community's association patterns, which can influence mating tactics. The St. Johns River (SJR) bottlenose dolphin (Tursiops erebennus) community was impacted by the 2013–2015 unusual mortality event (UME), caused by cetacean morbillivirus, through mortality and social network changes. We analyzed male alliance stability and behavior from April 2011 through March 2017 with respect to the UME. During the UME, 12 first‐order alliance dyads ended due to a partner's death or disappearance. Alliance tactics varied: forming second‐order alliances (n = 21 alliances; teams of first‐order alliances), forming first‐order alliances (n = 13 alliances) or remaining unallied after an alliance dissolved (n = 8 individuals). During‐ and post‐UME, fewer allied males formed second‐order alliances (55%) compared to pre‐UME (68%). While the UME likely indirectly influenced alliance behavior through demographic changes, female presence and breeding season consistently influenced alliance associations and consortships (cooperatively flanking a female), indicating a reproductive function for SJR alliances. Increased consortships when a second‐order partner was present suggests second‐order alliances may provide consortship support against rival males. These results enhance our understanding of multilevel alliance reproductive benefits and demonstrate the adaptability of male mating tactics in response to disturbances resulting in demographic changes.

Immunolocalization of Two Neurotrophins, NGF and BDNF, in the Pancreas of the South American Sea Lion Otaria flavescens and Bottlenose Dolphin Tursiops truncatus.

In this study, we have investigated the immunolocalization of NGF (Nerve Growth Factor) and BDNF (Brain-Derived Neurotrophic Factor) in the pancreas of two species of marine mammals: Tursiops truncatus (common bottlenose dolphin), belonging to the order of the Artiodactyla, and Otaria flavescens (South American sea lion), belonging to the order of the Carnivora. Our results demonstrated a significant presence of NGF and BDNF in the pancreas of both species with a wide distribution pattern observed in the exocrine and endocrine components. We identified some differences that can be attributed to the different feeding habits of the two species, which possess a different morphological organization of the digestive system. Altogether, these preliminary observations open new perspectives on the function of neurotrophins and the adaptive mechanisms of marine mammals in the aquatic environment, suggesting potential parallels between the physiology of marine and terrestrial mammals.

Harbor porpoise displacement by a solitary bottlenose dolphin in the Baltic Sea

Harbor porpoise displacement by a solitary bottlenose dolphin in the Baltic Sea

Phthalates and fatty acid markers in free-ranging cetaceans from an insular oceanic region: Ecological niches as drivers of contamination

Plastic additives, such as phthalates, are ubiquitous contaminants that can have detrimental impacts on marine organisms and overall ecosystems' health. Valuable information about the status and resilience of marine ecosystems can be obtained through the monitoring of key indicator species, such as cetaceans. In this study, fatty acid profiles and phthalates were examined in blubber biopsies of free-ranging individuals from two delphinid species (short-finned pilot whale – Globicephala macrorhynchus, n = 45; common bottlenose dolphin – Tursiops truncatus, n = 39) off Madeira Island (NE Atlantic). This investigation aimed to explore the relations between trophic niches (epipelagic vs. mesopelagic), contamination levels, and the health status of individuals within different ecological and biological groups (defined by species, residency patterns and sex). Multivariate analysis of selected dietary fatty acids revealed a clear niche segregation between the two species. Di-n-butylphthalate (DBP), diethyl phthalate (DEP), and bis(2-ethylhexyl) phthalate (DEHP) were the most prevalent among the seven studied phthalates, with the highest concentration reached by DEHP in a bottlenose dolphin (4697.34 ± 113.45 ng/g). Phthalates esters (PAEs) concentration were higher in bottlenose dolphins (Mean ∑ PAEs: 947.56 ± 1558.34 ng/g) compared to pilot whales (Mean ∑ PAEs: 229.98 ± 158.86 ng/g). In bottlenose dolphins, DEHP was the predominant phthalate, whereas in pilot whales, DEP and DBP were more prevalent. Health markers suggested pilot whales might suffer from poorer physiological conditions than bottlenose dolphins, although high metabolic differences were seen between the two species. Phthalate levels showed no differences by ecological or biological groups, seasons, or years. This study is the first to assess the extent of plastic additive contamination in free-ranging cetaceans from a remote oceanic island system, underscoring the intricate relationship between ecological niches and contaminant exposure. Monitoring these chemicals and their potential impacts is vital to assess wild population health, inform conservation strategies, and protect critical species and habitats.

Dolphins, sharks, and barnacles: Use of photographs to examine intra- and inter-specific interactions in bottlenose dolphins in Mozambique.

Understanding interactions within and between species is crucial to ecological research. However, for cetaceans such interactions can be difficult to observe in the field. Photographs offer an opportunity to study intra- and inter-specific interactions, by capturing 'snapshots' of their occurrence over space and time. At-surface and underwater photographs of bottlenose dolphins (Tursiops aduncus) inhabiting Ponta do Ouro Partial Marine Reserve (PPMR), Mozambique, were used to examine evidence of interactions with other dolphins, predators and ectoparasites. Intra-specific scarring levels significantly differed by sex and age class, with males displaying more scarring than females. Similarly, adults had more scarring than juveniles or calves. Shark bites significantly differed in their distribution across dolphin body areas, with the dorsal side being more frequently wounded than the ventral side. The presence of barnacles was exclusive to fluke, dorsal and pectoral fins, and showed strong seasonal trends. Overall, this study demonstrates the value of photographs for examining marine ecological interactions. It provides the first insights regarding dolphin social behaviour, predation risk and health for this population. These in turn will support future research into the population dynamics and conservation of the PPMR dolphins, which is urgently required in the face of locally increasing anthropogenic pressures.

Bioinspired swept-curved blade design for performance enhancement of Darrieus wind turbine

The present research proposes novel swept-curved bioinspired blades for Darrieus wind turbine. The design was influenced by the curved flippers of the bottle-nose dolphin. The proposed model was designed using the Solidworks software, empirically tested for power improvement, later fine-tuned adopting high fidelity numerical modeling. An in-depth analysis comparing the traditional H-bladed turbine with the new-bladed design was performed using OpenFOAM. Further, an elaborate experimental observations on the proposed design suggest that the model with 0.6c forward sweep outperformed the rest. The efficiency of the curved blade was notably enhanced by 14.41%, in contrast to the conventional model, and the numerical analysis endorses this observation. The modified turbine blades have the maximum wind streamlines that converge toward the center of the blade's trailing edge due to the lateral shift, and the resulting convergence reduces blade tip losses. The modified blade models demonstrated improved angular acceleration at a given wind speed, indicating enhanced efficiency and superior self-starting capabilities. Notably, these improvements were evident even at a lower wind speed of 4.2 m/s compared to the traditional H-model.

Pulmonary vascular adaptations to hypoxia in elite breath-hold divers.

Elite breath-hold divers (BHD) possess several oxygen conserving adaptations to endure long dives similar to diving mammals. During dives, Bottlenose Dolphins may increase the alveolar ventilation (VA) to perfusion (Q) ratio to increase alveolar oxygen delivery. We hypothesized that BHD possess similar adaptive mechanisms during apnea. Pulmonary blood volume (PBV) was determined by echocardiography, 15O-H2O PET/CT, and cardiac MRi, (n = 6) during and after maximum apneas. Pulmonary function was determined by body box spirometry and compared to matched controls. After 2min of apnea, the PBV determined by echocardiography and 15O-H2O-PET/CT decreased by 26% and 41%, respectively. After 4min of apnea, the PBV assessed by echocardiography and cardiac MRi decreased by 48% and 67%, respectively (n = 6). Fractional saturation (F)O2Hb determined by arterial blood-gas-analyses collected after warm-up and a 5-minute pool-apnea (n = 9) decreased by 43%. Compared to matched controls (n = 8), spirometry revealed a higher total and alveolar-lung-capacity in BHD (n = 9), but a lower diffusion-constant. Our results contrast with previous studies, that demonstrated similar lung gas transfer in BHD and matched controls. We conclude that elite BHD 1) have a lower diffusion constant than matched controls, and 2) gradually decrease PBV during apnea and in turn increase VA/Q to increase alveolar oxygen delivery during maximum apnea. We suggest that BHD possess pulmonary adaptations similar to diving mammals to tolerate decreasing tissue oxygenation. This manuscript addresses novel knowledge on tolerance to hypoxia during diving, which is shared by elite breath-hold divers and adult diving mammals: Our study indicates that elite breath-hold divers gradually decrease pulmonary blood volume and in turn increase VA/Q, to increase alveolar oxygen delivery during maximum apnea to tolerate decreasing oxygen levels similar to the Bottlenose Dolphin.

Novel Gammaherpesvirus Infections in Narrow-Ridged Finless Porpoise (Neophocaena asiaeorientalis) and False Killer Whales (Pseudorca crassidens) in the Republic of Korea.

A female narrow-ridged finless porpoise (Neophocaena asiaeorientalis) stranded on a beach on Jeju Island showed epithelial proliferative skin lesions on its body. Two false killer whales (Pseudorca crassidens), caught using nets near Gangneung and Samcheok, respectively, had multiple plaques on their penile epidermis. Histological examination of the epidermis revealed that all the lesions had common features, including accentuated rete pegs, ballooning changes, and eosinophilic intranuclear inclusion (INI) bodies. Based on the histopathological results, herpesvirus infection was suspected, and thus further analysis was conducted using herpesvirus-specific primers. Based on nested polymerase chain reaction (PCR) tests using the herpesvirus-detectable primers, the PCR products demonstrated two fragments: a 222-base-pair (bp) sequence of the DNA polymerase gene, SNUABM_CeHV01, showing 96.4% identity with a bottlenose dolphin herpesvirus from the Jeju narrow-ridged finless porpoise; and a 222 bp sequence of the DNA polymerase gene, SNUABM_CeHV02, showing 95.95% identity with the same bottlenose dolphin herpesvirus from the Gangneung and Samcheok false killer whales. The significance of this study lies in its ability to demonstrate the existence of novel cetacean herpesviruses in South Korean seawater, representing an important step forward in studying potentially harmful pathogens that affect endangered whale and dolphin populations.

The Strait and the Sea Unsettling Scores

In this inquiry I build on my previous work on contemporary aesthetics to engage the media practices and bio-acoustic mappings of cetacean scientists, as well as fishers’ video diaries and sound cartographies of interactions with cetaceans. To these, I also juxtapose a contemporary composer, sound engineer, and media artist’s sonographic records of encounters with these decidedly intriguing marine mammals alas too often reduced to the moniker “charismatic”. Concretely, I zoom in on three media practices: the sound compositions of Ariel Guzik, founder of the Nature Expression and Resonance Lab, who designs and engineers instruments to communicate with grey whales, sperm whales, and bottle nose dolphins in the Sea of Cortez; the hydrophone recordings, spectrograms, drone footage, and photo-identifications by a team of cetacean ethologists and communication scientists who run a research vessel and a marine ecology lab in the Tyrrhenian Sea; and the multimedia online platforms of fishers who produce video diaries of potentially fatal interactions with orcas in the Strait of Gibraltar. These carefully selected and juxtaposed audiovisual practices are the graphic, acoustic, and musical fragments that compose the de-territorialized cartography I am calling The Strait and The Sea.

The bottlenose dolphin (Tursiops truncatus): a novel model for studying healthy arterial aging.

Endothelial function declines with aging and independently predicts future cardiovascular disease (CVD) events. Diving also impairs endothelial function in humans. Yet, dolphins, being long-lived mammals adapted to diving, undergo repetitive cycles of tissue hypoxia-reoxygenation and disturbed shear stress without manifesting any apparent detrimental effects, as CVD is essentially nonexistent in these animals. Thus, dolphins may be a unique model of healthy arterial aging and may provide insights into strategies for clinical medicine. Emerging evidence shows that the circulating milieu (bioactive factors in the blood) is at least partially responsible for transducing reductions in age-related endothelial function. To assess whether dolphins have preserved endothelial function with aging because of a protected circulating milieu, we tested if the serum (pool of the circulating milieu) of bottlenose dolphins (Tursiops truncatus) induces the same arterial aging phenotype as the serum of age-equivalent humans. We incubated conduit arteries from young and old mice with dolphin and human serum and measured endothelial function ex vivo via endothelium-dependent dilation to acetylcholine. Although young arteries incubated with serum from midlife/older adult human serum had lower endothelial function, those incubated with dolphin serum consistently maintained high endothelial function regardless of the age of the donor. Thus, studying the arterial health of dolphins could lead to potential novel therapeutic strategies to improve age-related endothelial dysfunction in humans.NEW & NOTEWORTHY We demonstrate that, unlike serum of midlife/older adult humans, age-matched dolphin serum elicits higher endothelial function ex vivo in young mouse carotid arteries, suggesting that the circulating milieu of bottlenose dolphins may be geroprotective. We propose that dolphins are a novel model to investigate potential novel therapeutic strategies to mitigate age-related endothelial dysfunction in humans.

Bray calls emitted by common bottlenose dolphins (Tursiops truncatus) in offshore waters of northeastern Brazil

Bray calls emitted by common bottlenose dolphins (<i>Tursiops truncatus</i>) in offshore waters of northeastern Brazil

Survey of severe acute respiratory syndrome coronavirus 2 in captive and free-ranging wildlife from Spain

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), considered a zoonotic agent of wildlife origin, can infect various animal species, including wildlife in free-range and captive environments. Detecting susceptible species and potential reservoirs is crucial for preventing the transmission, spread, genetic evolution, and further emergence of viral variants that are major threats to global health. This study aimed to detect exposure or acute infection by SARS-CoV-2 in 420 animals from 40 different wildlife species, including terrestrial and aquatic mammals, from different regions of Spain during the 2020–2023 coronavirus disease 19 (COVID-19) pandemic. In total, 8/137 animals were positive for SARS-CoV-2 antibodies against the receptor binding domain and/or viral nucleoprotein according to independent ELISAs. However, only one ELISA-positive sample of a captive bottlenose dolphin (Tursiops truncatus) tested positive for SARS-CoV-2 neutralizing antibodies with a low titre (SNT50 38.15) according to a virus neutralization test. Cetaceans are expected to have a high risk of infection with SARS-CoV-2 according to early predictive studies due to the similarity of their angiotensin converting enzyme 2 cell receptor to that of humans. Moreover, of 283 animals analysed for SARS-CoV-2 RNA using RT-qPCR, none tested positive. Our results reinforce the importance of considering cetaceans at risk for SARS-CoV-2 infection and support taking preventive biosecurity measures when interacting with them, especially in the presence of individuals with suspected or confirmed COVID-19. Although most animals in this study tested negative for acute infection or viral exposure, ongoing surveillance of wildlife species and potentially susceptible animals is important to prevent future spillover events and detect potential novel reservoirs.

Determination of Metal and Metalloids in Bottlenose Dolphins’ (Tursiops truncatus) Skin from the Yucatan Peninsula, Mexico

Determination of Metal and Metalloids in Bottlenose Dolphins’ (Tursiops truncatus) Skin from the Yucatan Peninsula, Mexico

Correction: Bottlenose dolphin (Tursiops truncatus) habitat partitioning in relation to age classes in the northwest Mediterranean Sea

Correction: Bottlenose dolphin (Tursiops truncatus) habitat partitioning in relation to age classes in the northwest Mediterranean Sea

Organochlorine pesticides in fat tissue of cetaceans at the Crimean coast of the Black Sea

Accumulation of persistent organochlorine pesticides (OCP) in fat tissue was examined for the mammals found released ashore along the Crimean coast of the Black Sea in 2018–2022. This group of animals is positioned at the top of food chain in the local marine ecosystem. Statistically significant dependence of the accumulation on sex (males are more contaminated than females) and age (adults and juveniles are more contaminated than calves and neonates) is found. Besides, the pesticides concentration in fat from dorsal tissue is generally higher than in fat from caudal stem, but the difference is not significant. In the tissue of harbor porpoises and common dolphins, the mean OCP concentration decreased in the order: p,p′-DDE &gt; β-HCH &gt; p,p′-DDD &gt; p,p′-DDT, whereas bottlenose dolphins had the order: p,p′-DDE &gt; p,p′-DDD &gt; β-HCH &gt; p,p′-DDT. The most common metabolites were DDE, and their accumulation was the highest. The concentration of DDD was considerably lower, and significant accumulation of DDT was observed rarely, so the mean concentration of these group of metabolites was the lowest.