Wild Dolphins Research Articles

Detailed Comparison of Acoustic Signals from Rehabilitated and Wild Franciscanas (Pontoporia blainvillei) Dolphins.

The franciscana dolphin is a small, vulnerable species often caught in artisanal gillnets. This study aims to provide a comprehensive assessment of their acoustic capabilities by using advanced equipment to collect a large dataset of wideband, continuous recordings. We examined the detailed acoustic signals of franciscana dolphins, comparing the sounds from rehabilitated dolphins in captivity with those of wild dolphins near fishing nets. Significant differences in acoustic characteristics were found between neonates and older dolphins, with juvenile and wild dolphins showing similar features. For the first time, repetition patterns in click production were identified, highlighting the importance of understanding the context of these sounds in regards to feeding and communication. This study emphasizes the need for detecting neonates for species protection and suggests the potential for developing acoustic classifiers specific to different age groups. Our findings offer valuable insights for conservation efforts and the development of protection strategies for franciscana dolphins.

Similarities and differences in gastrointestinal microbiomes between wild and human-cared spotted dolphins (Stenella attenuata) in natural waters

Despite the growing awareness on the importance of gut microbiomes, understanding marine mammal gut microbiomes remains limited due to difficulties in sampling. Spotted dolphins (Stenella attenuata) are widely spread oceanic cetaceans, and there is a gap in knowledge regarding their gut microbiology. In this study, we opportunistically collected samples from both wild and human-cared spotted dolphins in the southern waters of Hainan Island, China. This provided the opportunity to examine the composition and diversity of the gut microbial communities of this cetacean species. Since these dolphins inhabit a similar water environment, different food sources might be the primary factor distinguishing the gut microbiomes of wild and human-cared populations, offering valuable experimental material to investigate potential differences in gut microbial community structure among marine mammals in similar environments but with varying food sources. We found that the gastrointestinal microbial community structure of wild and human-cared dolphins demonstrated significant differences, both overall and at specific locations. However, no significant difference was observed in the microbial diversity of their gastrointestinal tracts, indicating that the disparities primarily lie in microbiota composition. Additionally, we detected numerous potentially pathogenic bacteria, suggesting a comprehensive future study of marine mammal gut microbiology. Such a study might involve determining health indicator factors associated with these microbiomes. Our study not only supplements information on the gut microbiology of spotted dolphins but also delves into the similarities and differences in gastrointestinal microbial communities within the same marine mammal species when food source variations play a significant role in their lives.

Changes in the users of the social‐ecological system around a reciprocal human‐dolphin relationship

Abstract In contrast to many contemporary negative human‐nature relationships, Indigenous Peoples and Local Communities have stewarded nature through cultural practices that include reciprocal contributions for both humans and nature. A rare example is the century‐old artisanal fishery in which net‐casting fishers and wild dolphins benefit by working together, but little is known about the persistence of the social‐ecological system formed around this cultural practice. Here, we frame the human‐dolphin cooperative fishery in southern Brazil as a social‐ecological system based on secondary data from the scientific and grey literature. To investigate the dynamics of this system, we survey the local and traditional ecological knowledge and examine potential changes in its main component—the artisanal fishers—over time and space. Over 16 years, we conducted four interview campaigns with 188 fishers in fishing sites that are more open (accessible) or closed (restricted) to external influence. We investigated their experience, engagement and economic dependence on dolphin‐assisted fishing, as well as the learning processes and transmission of the traditional knowledge required to cooperate with dolphins. Our qualitative data suggest that fishers using accessible and restricted fishing sites have equivalent fishing experience, but those in more restrictive sites tend to be more economically dependent on dolphins, relying on them for fishing year‐round. The traditional knowledge on how to cooperate with dolphins is mostly acquired via social learning, with a tendency for vertical learning to be frequent among fishers using sites more restrictive for outsiders. Experience, economic dependence and reliance on vertical learning seem to decrease recently, especially in the accessible site. Our quantitative analyses, however, suggest that some of these fluctuations were not significant. Our study outlines the key components of this social‐ecological system and identifies changes in the attributes of a main component, the users. These changes, when coupled with changes in other components such as governance and resource units (fish and dolphins), can have implications for the persistence of this cultural practice and the livelihoods of Local Communities. We suggest that continuous monitoring of this system can help to safeguard the reciprocal contributions of this human‐nature relationship in years to come. Read the free Plain Language Summary for this article on the Journal blog.

Investigating the effect of virtual reality glasses during inhaler therapy use in children: A randomized clinical trial

Abstract Objectives Virtual reality (VR) glasses have been used in the medical field, as they are perceived to be suitable for distracting children. In this study, we aimed to compare patients who received inhaler treatment with VR glasses with those who received treatment without the aid of any device in terms of treatment compliance. Materials and Methods A prospective, randomized controlled study was conducted on pediatric patients aged 2 to 5 years requiring inhaler treatment (salbutamol), with the informed consent of their families. Participating patients who received standard care were divided into three groups via randomization: roller coaster VR group, wild dolphin VR group, and no additional device group. The patients were observed during their 15-minute inhaler treatment, and the groups were compared in terms of crying times, pre- and post-treatment physician and family questionnaire data (Face, Legs, Activity, Cry, Consolabity Scale [FLACC], Modified Yale Anxiety Scale [MYPAS], Modifiye Parents’ Pain Measure [MPMM], Wong–Baker Faces Pain Rating Scale [WBS]), and respiratory rate (RR), peripheral oxygen saturation, and heart rate value changes to determine any differences between them. Results Post-treatment questionnaire scores, RR, crying duration, and efficacy of treatment exhibited significant differences in Groups 1 and 2 compared to the control group. A significant difference was found in the post-treatment RR between groups 1 and 2, but no difference was observed in the other parameters. Conclusions Utilizing VR glasses during inhaler therapy has the potential to minimize adverse effects, such as pain, and enhance the overall comfort of the treatment environment for patients.

Empathy for wildlife: The importance of the individual.

Because climate change and the biodiversity crisis are driven by human actions, determining psychological mechanisms underpinning support for environmental action is an urgent priority. Here, we experimentally tested for mechanisms promoting conservation-related motivation and behavior toward a flagship species, wild Tamanend's bottlenose dolphins. Following evidence that empathy increases prosocial motivations and behavior, and that the ability to identify individual humans promotes empathy, we tested whether this relationship applied to the ability to identify individual dolphins. Participants identified dolphins from their dorsal fins at above chance levels, and better individuation correlated with higher empathy for dolphins and higher willingness to pledge environmental behaviors. Pairing a narrative with an image of an injured dolphin leads to higher donations relative to a narrative alone. Our novel finding that the ability to individually identify dolphins relates to empathy and conservation-related behavior suggests pathways for strengthening environmental attitudes and behavior.

Lessons in Developing a Behavioral Coding Protocol to Analyze In-the-Wild Child–Robot Interaction Events and Experiments

Behavioral analyses of in-the-wild HRI studies generally rely on interviews or visual information from videos. This can be very limiting in settings where video recordings are not allowed or limited. We designed and tested a vocalization-based protocol to analyze in-the-wild child–robot interactions based upon a behavioral coding scheme utilized in wildlife biology, specifically in studies of wild dolphin populations. The audio of a video or audio recording is converted into a transcript, which is then analyzed using a behavioral coding protocol consisting of 5–6 categories (one indicating non-robot-related behavior, and 4–5 categories of robot-related behavior). Refining the code categories and training coders resulted in increased agreement between coders, but only to a level of moderate reliability, leading to our recommendation that it be used with three coders to assess where there is majority consensus, and thereby correct for subjectivity. We discuss lessons learned in the design and implementation of this protocol and the potential for future child–robot experiments analyzed through vocalization behavior. We also perform a few observational behavior analyses from vocalizations alone to demonstrate the potential of this field.

Non-invasive age estimation based on faecal DNA using methylation-sensitive high-resolution melting for Indo-Pacific bottlenose dolphins.

Age is necessary information for the study of life history of wild animals. A general method to estimate the age of odontocetes is counting dental growth layer groups (GLGs). However, this method is highly invasive as it requires the capture and handling of individuals to collect their teeth. Recently, the development of DNA-based age estimation methods has been actively studied as an alternative to such invasive methods, of which many have relied on used biopsy samples. However, if DNA-based age estimation can be developed from faecal samples, age estimation can be performed entirely non-invasively. We developed an age estimation model using the methylation rate of two gene regions, GRIA2 and CDKN2A, measured through methylation-sensitive high-resolution melting (MS-HRM) from faecal samples of wild Indo-Pacific bottlenose dolphins (Tursiops aduncus). The age of individuals was known through conducting longitudinal individual identification surveys underwater. Methylation rates were quantified from 36 samples collected from 30 individuals. Both gene regions showed a significant correlation between age and methylation rate. The age estimation model was constructed based on the methylation rates of both genes which achieved sufficient accuracy (after LOOCV: MAE = 5.08, R2 = 0.33) for the ecological studies of the Indo-Pacific bottlenose dolphins, with a lifespan of 40-50 years. This is the first study to report the use of non-invasive faecal samples to estimate the age of marine mammals.

A review of the effect of various type of artificial sounds to odontocetes

Reactions of bottlenose dolphins, Pacific white-sided dolphins, false killer whales, Risso's dolphins, Dall's porpoises to artificial underwater sounds were observed for developing countermeasures to reduce by-catch on gill nets. Related papers published during 1980-1995 in Japan were re-visited. Various sound projectors having dominant frequencies from 2 kHz to 200 kHz with source levels reaching up to 200dB re 1μPa. Reactions of dolphins and porpoises to the sounds were observed in a pool, a net enclosure, or an open sea. Clear escaping reactions from a sound source were observed by sounds with exposed level above 170dB at the subject animal. Reactions to sounds below 160dB were not stable. The dolphins got accustomed to the sound after multiple projections. On the other hand, frequency and amplitude modulated sounds seemed to be effective even if the sound pressure level was about 120dB. Efficacy of acoustic pingers to control wild dolphins and porpoises was limited. The exposure level to change behavior was estimated above 170dB that depends on the source level of a device and distance to the animal. Acclimation for the sounds by dolphins and porpoises were not negligible. Avoiding successive transmission and amplitude/frequency modulations induced behavioral reactions.

Rehabilitation of captive Indo-Pacific bottlenose dolphin (Tursiops aduncus) as a way to combat the effects of climate change

Climate change caused by human industrialization is an unavoidable global problem which started in the 20th century. The high concentration of greenhouse gases has caused global warming, natural disaster, rising sea level, and threatened marine wildlife. It has been proven to decrease the survival rate of dolphins by 12%. This research aims to describe the behavior and assess the readiness to release rehabilitated Tursiops aduncus in Umah Lumba, Banyuwedang Bay, Bali, to boost the wild dolphin population. Visual observation was made on three individuals: Rambo, Rocky and Johnny, at Umah Lumba, Banyuwedang Bay Bali, on March 2021, who have been in the rehabilitation facility since September 2019. The three individuals can be identified by the physical characteristics of their head, mandible, and dorsal fin. The dolphins have developed nine wild-dolphin-like behaviors: respiratory, exploratory, resting, reproductive, social, predatory, spy-hopping, tail-clapping, and sneezing. This rehabilitation program is essential because it increases the population of wild dolphins by acclimating, adapting, and training former captive dolphins for release.

The fate of a century-old partnership between humans and dolphins

Aligning human interests and wildlife protection requires a deep understanding of human-wildlife interactions. Behavioral tracking and demographic surveys show that foraging synchrony is key to generate short- and long-term benefits for human fishers and wild dolphins. We used simulations to describe the conditions under which this cooperation can turn into another human-wildlife conflict.

Seasonal and diel patterns in Pacific white‐sided dolphin (Lagenorhynchus obliquidens) pulsed calls near Barkley Canyon

AbstractEvaluation of temporal patterns in offshore marine mammal activity through visual data collection can be impaired by light and weather conditions and the cost of ship time. The conditions‐independence and cost‐efficacy of acoustic data collection make it popular for researching the temporal patterns of wild dolphins. However, Pacific white‐sided dolphins (PWSDs) north of Southern California remain under‐researched. This study evaluates diel and seasonal patterns in PWSD communication signals detected in 480 days of near‐continuous passive acoustic data collected over 20 months from the Barkley Canyon node of Ocean Networks Canada's NEPTUNE observatory, offshore Vancouver Island, British Columbia, Canada. In this study, a random forest classifier is used to identify PWSD pulsed calls and false positives are manually removed. The resulting acoustic presence‐absence data set is evaluated for seasonal and diel patterns using generalized additive mixed models, considering masking effects from ambient noise. PWSDs are found to be vocally active during all diel periods year‐round, with high summer and low spring activity. Seasonally dependent diel patterns are identified, with PWSD pulsed calls exhibiting no diel pattern in spring, a slight increase in vocal activity during dusk and night in fall and winter, and a notable increase during night and dawn in summer.

Sex bias in mortality risk changes over the lifespan of bottlenose dolphins.

Research on sex biases in longevity in mammals often assumes that male investment in competition results in a female survival advantage that is constant throughout life. We use 35 years of longitudinal data on 1003 wild bottlenose dolphins (Tursiops aduncus) to examine age-specific mortality, demonstrating a time-varying effect of sex on mortality hazard over the five-decade lifespan of a social mammal. Males are at higher risk of mortality than females during the juvenile period, but the gap between male and female mortality hazard closes in the mid-teens, coincident with the onset of female reproduction. Female mortality hazard is non-significantly higher than male mortality hazard in adulthood, resulting in a moderate male bias in the oldest age class. Bottlenose dolphins have an intensely male-competitive mating system, and juvenile male mortality has been linked to social competition. Contrary to predictions from sexual selection theory, however, male-male competition does not result in sustained male-biased mortality. As female dolphins experience high costs of sexual coercion in addition to long and energetically expensive periods of gestation and lactation, this suggests that substantial female investment in reproduction can elevate female mortality risk and impact sex biases in lifespan.

The fitness consequences of human‐wildlife interactions on foraging common bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida

AbstractHuman‐wildlife interactions (HI) are becoming more prevalent with increasing human population. These interactions could have important eco‐evolutionary consequences that become apparent only after observing populations for multiple generations. Here, we analyzed 28 years (1993–2020) of data from the world's longest‐running study of a wild dolphin population to assess the fitness consequences of HI on common bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida. We investigated how human‐related foraging activities such as depredation, begging, and patrolling mediate reproductive output and reproductive success of conditioned (HI) and unconditioned (non‐HI) females. The analysis of 84 females and their 286 calves born during 1993–2020 found a confluence of effects on individual fitness. Reproductive output of females engaging in moderate levels of human‐related foraging was 94% greater than that of non‐HI females. However, high frequencies of human‐related foraging had a negative effect on female reproductive success by increasing the risk of calf death up to nine times when compared to non‐HI females, resulting in 31% less calf survival. These findings provide evidence that human‐wildlife interactions have considerable potential to catalyze population‐level changes by altering individual fitness, and demonstrate the value of comprehensive, long‐term data to better understand the ecological and evolutionary implications of human‐wildlife conflict.

Bottlenose dolphin mothers modify signature whistles in the presence of their own calves

Human caregivers interacting with children typically modify their speech in ways that promote attention, bonding, and language acquisition. Although this "motherese," or child-directed communication (CDC), occurs in a variety of human cultures, evidence among nonhuman species is very rare. We looked for its occurrence in a nonhuman mammalian species with long-term mother-offspring bonds that is capable of vocal production learning, the bottlenose dolphin (Tursiops truncatus). Dolphin signature whistles provide a unique opportunity to test for CDC in nonhuman animals, because we are able to quantify changes in the same vocalizations produced in the presence or absence of calves. We analyzed recordings made during brief catch-and-release events of wild bottlenose dolphins in waters near Sarasota Bay, Florida, United States, and found that females produced signature whistles with significantly higher maximum frequencies and wider frequency ranges when they were recorded with their own dependent calves vs. not with them. These differences align with the higher fundamental frequencies and wider pitch ranges seen in human CDC. Our results provide evidence in a nonhuman mammal for changes in the same vocalizations when produced in the presence vs. absence of offspring, and thus strongly support convergent evolution of motherese, or CDC, in bottlenose dolphins. CDC may function to enhance attention, bonding, and vocal learning in dolphin calves, as it does in human children. Our data add to the growing body of evidence that dolphins provide a powerful animal model for studying the evolution of vocal learning and language.

Difference analysis of respiratory pore flora between dolphins in the wild and in captivity

Abstract Dolphins are marine mammals with unique anatomical structures in their airways. These particular respiratory structures make dolphins very sensitive to microorganisms in the air, and the habitats of dolphins in captivity and in the wild are quite different. This causes captive dolphins to suffer from illnesses, especially respiratory diseases. Previous studies have shown that the respiratory flora plays an essential role in the health of humans and animals. Therefore, by comparative analysis of the respiratory flora of wild dolphins and dolphins in captivity, we want to find the flora related to dolphins’ respiratory diseases, and try to improve dolphin health through flora homeostasis. For this purpose, we performed 16S rRNA gene sequencing and analyses. We found that Proteobacteria, Firmicutes, Actinobacteria, Campilobacterota, Paracoccus, and other flora differed between wild and healthy and sub-healthy captive dolphins. Some of them are the dominant flora for promoting health, and the others may be essential pathogenic bacteria in the sub-healthy state of dolphins in captivity.

Observations and Detailed Descriptions of Sociosexual Behavior in Wild Indo-Pacific Bottlenose Dolphins (Tursiops aduncus)

Sociosexual behavior is not directly related to reproduction. It is observed between mature and immature individuals of both sexes and interactions can be between mixed- or same-sex individuals. This behavior may have important social functions. We observed and recorded the sociosexual behavior of wild Indo-Pacific bottlenose dolphins (Tursiops aduncus), underwater off Mikura Island, Japan, with regards to erection and mounting. This behavior was observed mainly between mothers and sons and in groups of subadult males (age 1–13 years). In subadult males, mounting behavior toward one passive individual from two or more individuals playing an active role, occurred in most cases. This behavior involving three or more participants has rarely been observed in other animal species, except for bowhead whales (Balaena mysticetus), common bottlenose dolphins (T. truncatus), and beluga whales (Delphinapterus leucas). Sociosexual behavior in the Mikura Island dolphins may not be agonistic because individuals in the passive role did not try to escape from the individuals playing the active role. Further studies on sociosexual behavior T. aduncus could reveal the social functions of this behavior, such as younger animals practicing mating behaviors required as adults and developing their relationships for when they are adults.

Yawning in Wild Indo-Pacific Bottlenose Dolphins (Tursiops aduncus)

Yawning in Wild Indo-Pacific Bottlenose Dolphins (Tursiops aduncus)

Group definition for underwater observation of wild Indo-Pacific bottlenose dolphins

Group definition for underwater observation of wild Indo-Pacific bottlenose dolphins

Foraging synchrony drives resilience in human–dolphin mutualism

Interactions between humans and nature have profound consequences, which rarely are mutually beneficial. Further, behavioral and environmental changes can turn human-wildlife cooperative interactions into conflicts, threatening their continued existence. By tracking fine-scale behavioral interactions between artisanal fishers and wild dolphins targeting migratory mullets, we reveal that foraging synchrony is key to benefiting both predators. Dolphins herd mullet schools toward the coast, increasing prey availability within the reach of the net-casting fishers, who gain higher foraging success-but only when matching the casting behavior with the dolphins' foraging cues. In turn, when dolphins approach the fishers' nets closely and cue fishers in, they dive for longer and modify their active foraging echolocation to match the time it takes for nets to sink and close over mullets-but only when fishers respond to their foraging cues appropriately. Using long-term demographic surveys, we show that cooperative foraging generates socioeconomic benefits for net-casting fishers and ca. 13% survival benefits for cooperative dolphins by minimizing spatial overlap with bycatch-prone fisheries. However, recent declines in mullet availability are threatening these short- and long-term benefits by reducing the foraging success of net-casting fishers and increasing the exposure of dolphins to bycatch in the alternative fisheries. Using a numerical model parametrized with our empirical data, we predict that environmental and behavioral changes are pushing this traditional human-dolphin cooperation toward extinction. We propose two possible conservation actions targeting fishers' behavior that could prevent the erosion of this century-old fishery, thereby safeguarding one of the last remaining cases of human-wildlife cooperation.

Sixteen years later: an updated evaluation of the impacts of chronic human interactions with bottlenose dolphins (Tursiops truncatus truncatus) at Panama City, Florida, USA

Panama City, Florida is considered a notorious ‘hot spot’ in the southeastern United States for chronic illegal feeding and harassment of bottlenosedolphins. The nature and extent of these interactions was evaluated by Samuels and Bejder (2004); they concluded that food provisioning was thebasis for human interactions with wild dolphins, and that these encounters were likely harmful to dolphins. A follow-up study was conducted in2014 to reassess the current state of human interactions with wild dolphins. The number of conditioned dolphins (n = 21) tripled compared to theprevious study. Both studies found conditioned dolphins engaged in human interaction events during approximately 75% of observable time pointswhen vessels or swimmers were present. In this study, conditioned dolphins spent as much as 81% of their time begging or patrolling and significantlydecreased their distance moved while doing so. Nested multinomial regression analysis revealed conditioned dolphins engaged in resting or foraging(i.e. natural) behaviour were extremely likely to switch to begging or patrolling (i.e. interaction) behaviours when vessels or swimmers were present.Numerous high risk situations were observed for both conditioned dolphins and humans during these interactions. The latest development in illegalfeeding was documented: bait boats feeding dolphins to lure the animals into interactions with tour vessels and swimmers. Our observations indicatethat the problem in Panama City has escalated: dolphins are being actively provisioned, often for long periods of time; the proportion of conditioneddolphins has increased; interacting dolphins and humans are both at increased risk for injury, illness, or death; and conditioned dolphin activitybudgets and movement patterns continue to be negatively impacted by human behaviour. We recommend a more aggressive management strategy,such as targeted and sustained enforcement of existing regulations as well as additional restrictions that prohibit close approaches and in-waterinteractions for Panama City in order to curtail continued harassment of dolphins and reduce the risk of injury for both humans and dolphins.