Tursiops Research Articles

Behavior reference intervals and activity budgets of bottlenose dolphins in accredited zoos and aquariums

Knowledge of the spectrum and frequency of species-appropriate behaviors is valuable when evaluating the welfare of animals living under professional care. Dolphins have a rich behavioral repertoire and behavioral metrics have been used to quantify behavior. Data in the present study were collected as part of a larger study titled “Towards understanding the welfare of cetaceans in zoos and aquariums” (colloquially called the Cetacean Welfare Study). Behavior data were collected on 43 common bottlenose dolphins (Tursiops truncatus) at 23 facilities. Dolphins were video recorded three times per week for 25 min over one five-week data collection period between July and November of 2018 and a second five-week data collection period between January and April of 2019. Solo and group swimming were the two most common behavior states for dolphins. Group active, chase, fast swimming, tactile, and ventral swimming were significantly impacted by age. Interacting with conspecifics was significantly impacted by time of day. The rate of fluke-out dives was associated with sex. Behavioral diversity was significantly impacted by age and sex. The findings presented here are representative of behavioral observations collected from the largest number of individuals in the largest number of zoo and aquarium habitats that have been published to date. These results provide the first normal reference intervals for behavior and a comprehensive activity budget that encompasses the behavior of dolphins living in a variety of accredited zoo and aquarium habitat types and social structures. The activity budgets and reference intervals are valuable as a tool for monitoring welfare and for increasing our understanding of typical dolphin behavior across broad environmental and management conditions.

Dolphin interactions with tuna feedlots at Port Lincoln, South Australia and recommendations for minimising entanglements

Cetacean carcasses near Port Lincoln and entanglements in southern blue-fin tuna feedlots were monitored between 1990 and 1999. Dolphins became entangled and died in large-mesh (usually > 15cm) anti-predator nets around the cages, from surface to seafloor (18m). The carcasses were retrieved and studied with respect to diet and life history. During the period of study, 29 dolphins (15 bottlenose, 9 common, 5 unidentified) were confirmed entanglement deaths and an additional eight unconfirmed reports of dead dolphins were made between 1993 and 1996. Beach-washed or floating carcasses of an additional 38 dolphins were found in the Port Lincoln region during 1990-1999, four of which were suspected entanglements. The carcasses of 23 entangled and four suspected entangled dolphins were studied for diet, and reproductive and relative age characteristics. At least 24 of the 33 entangled animals were juveniles or sexually mature animals, of which most of the females were pregnant or lactating. Three calves and no neonates were entangled. Gastrointestinal contents of 57 bottlenose and common dolphins from elsewhere along the coast of South Australia were also studied. Cephalopods were more abundant in bottlenose dolphins than common dolphins, including those entangled in tuna feedlots. Carangidae were the main identified fish prey of dolphins entangled in tuna nets. The study concluded that dolphins were being attracted to, and feeding in, the area of the cages. Recommendations for minimising entanglements include removing anti-predator nets or reducing mesh size to less than 8cm, reducing tuna food wastes and thereby the food source for other fish in the vicinity, and rigorous monitoring of both entanglements and dolphin populations in the Port Lincoln region.

Serum Protein Concentration and Serum Protein Fractions in Bottlenose Dolphins (Tursiops truncatus) under Human Care Using Agarose Gel Electrophoresis.

Serum protein electrophoresis (SPE) is the most used and reliable method to determine the percentage of serum protein subfractions. The interpretation of the kinetics of total proteins and albumin and globulin fractions is receiving increased attention in wild animals, as well as in domestic animals, due to the possibility of identifying typical pathologic patterns. However, the interpretation of these data had to be performed in light of an appropriate method-and species- specific reference intervals (RIs). In marine mammals, as well as other non-domestic species, specific attention should also be given to the different environment (free ranging vs. human managed) and the associated different exposure to environmental stimuli. The aim of this report was to establish RIs for the serum protein fractions evaluated using agarose gel electrophoresis (AGE) in bottlenose dolphins under human care. Peripheral blood samples were collected from 40 bottlenose dolphins during standard veterinary procedures to evaluate their health status. Total protein concentration was determined using the biuret method while AGE was performed using an automated system. A pooled dolphin's serum sample was used to determine the intra-assay and inter-assay imprecision of AGE. The RIs were calculated using an Excel spreadsheet with the Reference Value Advisor set of macroinstructions. The intra and inter-assay imprecisions were 1.2% and 2.5%, respectively, for albumin; 2.9% and 5.7%, respectively, for α-globulins; 3.8% and 4.0%, respectively, for β-globulins; and 3.4% and 4.8%, respectively, for γ-globulins. The total protein, albumin, α-globulin, β-globulin, and γ-globulin concentrations were 65.5 ± 5.4 g/L, 45.5 ± 4.9 g/L, 8.0 ± 1.0 g/L, 5.0 ± 2.0 g/L, and 7.0 ± 2.0 g/L, respectively. We established the RIs for the total protein and serum protein fractions using AGE in bottlenose dolphins under human care.

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.

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.

A Quantitative Assessment of Trainers-Dolphins' Interactions in the Absence of Food Reward.

All the studies that have considered the motivation of the dolphins to interact with their trainers as a possible welfare indicator have been carried out in facilities where the trainer-dolphin interactions (TDIs) sessions were reinforced with food. Therefore, in these specific circumstances, it was difficult to separate the motivation of the dolphins interacting with the trainers from the food drive. The current study aims to assess the interaction between the trainers and the dolphins in the absence of food rewards. The research was carried out at The Dolphin Reef (Eilat, Israel), a facility where the interaction between the trainers and 14 bottlenose dolphins of different sex and age classes did not involve food rewards. A total of 531 TDIs were recorded, with dolphins participating in 94.5% of the sessions and an average of three dolphins per session. The dolphins participated in a higher number and more frequently in the TDIs when toys were provided by the trainers. Diel and seasonal differences were also observed, with the dolphins participating more during the morning sessions and the neutral season. The latency of response of the dolphins to the presence of the trainers on the platform or in the water, whether or not advertised by the trainers' signal ("call" or "no-call"), was very short (usually less than 1 min), and the dolphins often anticipated the beginning of the sessions by arriving at the trainers' location before or upon the caretakers' arrival (96% of the time). Individual differences in the participation in the TDIs were also recorded, which might be linked to both the dolphin's health/welfare status or their personality. The current study shows that the separation of the TDIs from the food reward allows for a better understanding of the willingness of dolphins under human care to interact with their trainers. In addition, the results presented in this paper show that such TDIs are an important part of these dolphins' lives, which suggests that these interactions might be an additional tool to improve the animals' social environment and monitor their welfare.

Site Fidelity of Coastal Bottlenose Dolphins (Tursiops truncatus) off Southeast Florida, USA

The coastal bottlenose dolphin is well studied throughout its natural range, though most research focuses on wide, well-protected habitats such as bays and estuaries rather than on narrow coastal sand banks. This study identifies a residential group of coastal bottlenose dolphins utilizing the northwestern Atlantic waters off the coast of Palm Beach County, Florida. From 2014 to 2020, 313 boat surveys were conducted, and 585 individual dolphins were identified using photo-identification. Using seasonal and annual resighting ratios, 24 dolphins were considered full-time residents, 66 dolphins were considered part-time residents, and 478 dolphins were transient. The presence of individuals with high site fidelity indicates that the region is used as a permanent habitat for some individuals, while the presence of transient animals may indicate a possible bridge between populations living to the north and south of the region.

Affiliative Behavior After Aggressions in Common Bottlenose Dolphins (Tursiops truncatus)

Affiliative behavior in social animals may have several functions such as maintaining social bonds, reducing tensions, or restoring relationships. Common bottlenose dolphins (Tursiops truncatus) engage in several affiliative behaviors, including parallel swimming, contact swimming, and flipper rubbing. Dolphins affiliate with former opponents after aggression, suggesting that this is a function of tension reduction. This study investigated how affiliative behaviors occur after aggression. Parallel swimming occurred more frequently than expected after aggression, while contact swimming and flipper rubbing occurred less frequently than expected. Parallel swimming and contact swimming occurred immediately after aggression; in contrast, flipper rubbing tended to occur more than one minute after aggression. These results suggest that common bottlenose dolphins engage in parallel swimming and contact swimming when social tension increases. The function may differ among these affiliative behaviors, and dolphins may engage in specific affiliations after aggression.

Reconstructing the colonization history of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Northwestern Australia.

Bottlenose dolphins (Tursiops spp.) are found in waters around Australia, with T. truncatus typically occupying deeper, more oceanic habitat, while T. aduncus occur in shallower, coastal waters. Little is known about the colonization history of T. aduncus along the Western Australian coastline; however, it has been hypothesized that extant populations are the result of an expansion along the coastline originating from a source in the north of Australia. To investigate the history of coastal T. aduncus populations in the area, we generated a genomic SNP dataset using a double-digest restriction-site-associated DNA (ddRAD) sequencing approach. The resulting dataset consisted of 103,201 biallelic SNPs for 112 individuals which were sampled from eleven coastal and two offshore sites between Shark Bay and Cygnet Bay, Western Australia. Our population genomic analyses showed a pattern consistent with the proposed source in the north with significant isolation by distance along the coastline, as well as a reduction in genomic diversity measures along the coastline with Shark Bay showing the most pronounced reduction. Our demographic analysis indicated that the expansion of T. aduncus along the coastline began around the last glacial maximum and progressed southwards with the Shark Bay population being founded only 13 kya. Our results are in line with coastal colonization histories inferred for Tursiops globally, highlighting the ability of delphinids to rapidly colonize novel coastal niches as habitat is released during glacial cycle-related global sea level and temperature changes.

Unusual occurrence of a mixed pod of false killer whales (Pseudorca crassidens) and common bottlenose dolphins (Tursiops truncatus) in the Beagle Channel (Argentina)

Unusual occurrence of a mixed pod of false killer whales (Pseudorca crassidens) and common bottlenose dolphins (Tursiops truncatus) in the Beagle Channel (Argentina)

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.

Cooperation increases bottlenose dolphins' (Tursiops truncatus) social affiliation.

Dolphins live in a fission-fusion society, where strong social bonds and alliances can last for decades. However, the mechanism that allows dolphins to form such strong social bonds is still unclear. Here, we hypothesized the existence of a positive feedback mechanism in which social affiliation promotes dolphins' cooperation, which in turn promotes their social affiliation. To test it, we stimulated the cooperation of the 11 dolphins studied by providing a cooperative enrichment tool based on a rope-pulling task to access a resource. Then we measured the social affiliation [simple ratio index (SRI)] of each possible pair of dolphins and evaluated whether it increased after cooperation. We also evaluated whether, before cooperation, pairs that cooperated had a higher SRI than those that did not cooperate. Our findings showed that the 11 cooperating pairs had significantly stronger social affiliation before cooperation than the 15 non-cooperating pairs. Furthermore, cooperating pairs significantly increased their social affiliation after cooperation, while non-cooperating pairs did not. As a result, our findings provide support to our hypothesis, and suggest that the previous social affiliation between dolphins facilitates cooperation, which in turn promotes their social affiliation.

Using Blood Gas Analysis and Capnography to Determine Oxygenation Status in Bottlenose Dolphins (Tursiops truncatus) Following the Deepwater Horizon Oil Spill.

Following the Deepwater Horizon (DWH) oil spill in 2010, poor pulmonary health and reproductive failure in bottlenose dolphins (Tursiops truncatus) in the northern Gulf of Mexico were well-documented. One postulated etiology for the increased fetal distress syndrome and pneumonia found in affected perinatal dolphins was maternal hypoxia caused by lung disease. The objective of this study was to evaluate the utility of blood gas analysis and capnography in determining oxygenation status in bottlenose dolphins with and without pulmonary disease. Blood and breath samples were collected from 59 free-ranging dolphins in Barataria Bay, Louisiana (BB), during a capture-release health assessment program, and from 30 managed dolphins from the U.S. Navy Marine Mammal Program in San Diego, CA. The former was the oil-exposed cohort and the latter served as a control cohort with known health histories. Capnography and select blood gas parameters were compared based on the following factors: cohort, sex, age/length class, reproductive status, and severity of pulmonary disease. Animals with moderate-severe lung disease had higher bicarbonate concentrations (p = 0.005), pH (p < 0.001), TCO2 (p = 0.012), and more positive base excess (p = 0.001) than animals with normal-mild disease. Capnography (ETCO2) was found to have a weak positive correlation with blood PCO2 (p = 0.020), with a mean difference of 5.02 mmHg (p < 0.001). Based on these findings, indirect oxygenation measures, including TCO2, bicarbonate, and pH, show promise in establishing the oxygenation status in dolphins with and without pulmonary disease.

Fine‐scale spatial and temporal distribution patterns of large marine predators in a biodiversity hotspot

AbstractAimLarge marine predators, such as cetaceans and sharks, play a crucial role in maintaining biodiversity patterns and ecosystem function, yet few estimates of their spatial distribution exist. We aimed to determine the species richness of large marine predators and investigate their fine‐scale spatiotemporal distribution patterns to inform conservation management.LocationThe Hauraki Gulf/Tīkapa Moana/Te Moananui‐ā‐Toi, Aotearoa/New Zealand.MethodsWe conducted a replicate systematic aerial survey over 12 months. Flexible machine learning models were used to explore relationships between large marine predator occurrence (Bryde's whales, common and bottlenose dolphins, bronze whaler, pelagic and immature hammerhead sharks) and environmental and biotic variables, and predict their monthly distribution and associated spatially explicit uncertainty.ResultsWe revealed that temporally dynamic variables, such as prey distribution and sea surface temperature, were important for predicting the occurrence of the study species and species groups. While there was variation in temporal and spatial distribution, predicted richness peaked in summer and was the highest in coastal habitats during that time, providing insight into changes in distributions over time and between species.Main ConclusionsTemporal changes in distribution are not routinely accounted for in species distribution studies. Our approach highlights the value of multispecies surveys and the importance of considering temporally variable abiotic and biotic drivers for understanding biodiversity patterns when informing ecosystem‐scale conservation planning and dynamic ocean management.

Differences in the whistles of two ecotypes of bottlenose dolphins from the Gulf of California.

Intraspecific whistle variation in dolphins has been explained in the context of geographical isolation, soundscape, and social structure. Whistles of two ecotypes of bottlenose dolphins from La Paz Bay, Gulf of California, were analyzed. Both ecotypes showed similar whistle contours. However, they could be identified by contour maximum frequency which was predominantly above 15 kHz for oceanic dolphins and below 15 kHz for coastal dolphins. The different whistle frequencies of the two ecotypes could result from differences in group size and acoustic characteristics of their respective habitats, suggesting potential future passive acoustic monitoring applications.

Stereological assessment of immunohistochemical markers in the auditory nuclei of bottlenose dolphins

Stereological assessment of immunohistochemical markers in the auditory nuclei of bottlenose dolphins

Dolphin leukocytes exhibit an attenuated cytokine response and increase heme oxygenase activity upon exposure to lipopolysaccharides

Cetaceans exhibit physiological adaptations that allowed the transition to aquatic life, including a robust antioxidant defense system that prevents injury from repeated exposure to ischemia/reperfusion events associated with breath-hold diving. The signaling cascades that characterize ischemic inflammation in humans are well characterized. In contrast, cetaceans' molecular and biochemical mechanisms that confer tolerance to inflammatory events are poorly understood. Heme oxygenase (HO) is a cytoprotective protein with anti-inflammatory properties. HO catalyzes the first step in the oxidative degradation of heme. The inducible HO-1 isoform is regulated by various stimuli, including hypoxia, oxidant stress, and inflammatory cytokines. The objective of this study was to compare the response of HO-1 and cytokines to a proinflammatory challenge in leukocytes isolated from humans and bottlenose dolphins (Tursiops truncatus). We measured changes in HO activity, and abundance and expression of interleukin 1 beta (IL-1β), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), and heme oxygenase 1 (HMOX1) in leukocytes treated with lipopolysaccharide (LPS) for 24 and 48 h. HO activity increased (p < 0.05) in dolphin (48 h) but not human cells. TNF-α expression increased in human (24 h, 48 h), but not dolphin cells following LPS stimulation. LPS-induced cytokine expression was lower in dolphin than in human leukocytes, suggesting a blunted cytokine response in bottlenose dolphin leukocytes treated with LPS. Results suggest species-specific regulation of inflammatory cytokines in leukocytes treated with LPS, which may lead to differential responses to a pro-inflammatory challenge between marine and terrestrial mammals.

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

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

Akhi A.V. Efficiency of Identification of Complex Noise-Like Signal Classes by Dolphins (&lt;i&gt;Tursiops truncatus&lt;/i&gt;) under Simultaneous Presentation Spatial Uncertainty

The possibility of dolphin’s auditory system to solve the complex problem of identifying and classifying noise-like signals according to certain invariant features is considered under conditions of spatial uncertainty of their simultaneous presentation. There was studied the ability of bottlenose dolphins, which were trained to recognize and classify such signals, to select a certain class of signals from several that sound simultaneously. The dolphin had to recognize a positive class signal with a pair of simultaneously sounding signals: positive-negative (alternative choice) and with simultaneously sounding three signals: positive-negative-negative (multiple choice). It’s shown that the dolphin effectively solves the problem with a simple alternative choice of two signal sources, at the limit of reliability when choosing from three sources and unreliable when choosing from more sources.

Using Anticipatory Behavior to Detect the Change in Interest in an Activity Repeated Several Times and Avoid Habituation in Bottlenose Dolphins (Tursiops Truncatus)

ABSTRACT Environmental enrichment is an essential component of the management policies used by zoos and aquaria to promote animals’ welfare. However, when enrichments are provided several times, they can cause habituation and lose their enrichment effects. A simple method to avoid it could be making a preventive assessment about the trend of animals’ interest in a stimulus provided several times. Here, we hypothesized that anticipatory behavior could be used to assess the decrease in interest in playing with objects when the activity is repeated. Moreover, we also assumed that this could be done before providing objects to play with. Our results support this hypothesis. Specifically, we found a positive correlation between the time the 7 dolphins tested spent performing anticipatory behavior before the enrichment sessions and the time they spent playing with objects during those sessions. As a result, anticipatory behavior performed before enrichment sessions predicted dolphins’ interest in the session and allowed us to assess whether the sessions had lost their enrichment effect.