Captive Dolphins Research Articles

Echolocation in wild toothed whales

Don Griffin showed more than 50 years ago that bats echolocate for orientation and to capture prey. Experiments also demonstrated that captive dolphins can echolocate; more recent work parallels Griffin’s work with bats in the wild. Digital acoustic recording tags were attached to sperm and beaked whales, Ziphius cavirostris and Mesoplodon densirostris, to record outgoing clicks and incoming echoes. The sperm whale data show echoes from the sea surface and seafloor, which are probably used for orientation and obstacle avoidance. When diving, sperm whales adjust their interclick interval as they change their pitch angle, consistent with the hypothesis that they are echolocating on a horizontal layer at the depth at which they will feed. This suggests that they may be listening for volume reverberation to select a prey patch. The beam pattern of sperm whales includes a narrow, forward-directed high-frequency beam probably used for prey detection, and a broader, backward-directed lower-frequency beam probably used for orientation. Beaked whales produce directional clicks with peak frequencies in the 25–40-kHz region. Echoes from individual prey items have been detected from clicks of beaked whales. This opens a new window into the study of how animals use echolocation to forage in the wild.

Captive dolphins, Tursiops truncatus, develop signature whistles that match acoustic features of human-made model sounds.

This paper presents a cross-sectional study testing whether dolphins that are born in aquarium pools where they hear trainers' whistles develop whistles that are less frequency modulated than those of wild dolphins. Ten pairs of captive and wild dolphins were matched for age and sex. Twenty whistles were sampled from each dolphin. Several traditional acoustic features (total duration, duration minus any silent periods, etc.) were measured for each whistle, in addition to newly defined flatness parameters: total flatness ratio (percentage of whistle scored as unmodulated), and contiguous flatness ratio (duration of longest flat segment divided by total duration). The durations of wild dolphin whistles were found to be significantly longer, and the captive dolphins had whistles that were less frequency modulated and more like the trainers' whistles. Using a standard t-test, the captive dolphin had a significantly higher total flatness ratio in 9/10 matched pairs, and in 8/10 pairs the captive dolphin had significantly higher contiguous flatness ratios. These results suggest that captive-born dolphins can incorporate features of artificial acoustic models made by humans into their signature whistles.

Evidence of Helicobacter sp. in dental plaque of captive dolphins (Tursiops gephyreus).

Gastrointestinal lesions have been extensively reported in wild and captive marine mammals. However, their etiology remains unclear. In humans and other animals, chronic gastritis and peptic ulcers have been associated with Helicobacter sp. Therefore, the aim of our study was to investigate the presence of Helicobacter sp. in the gastric juice, dental plaque, and saliva of marine mammals living in a controlled environment. Five dolphins (Tursiops gephyreus), one killer whale (Orcinus orca), one false killer whale (Pseudorca crassidens), three sea lions (Otaria flavescens), two elephant seals (Mirounga leonina), and two fur seals (Arctocephalus australis) were studied. Saliva, dental plaque, and gastric juice samples were examined for Helicobacter sp. using polymerase chain reaction. None of the gastric juice or saliva samples were positive for Helicobacter sp. However, Helicobacter sp. DNA was detected in dental plaque from two dolphins, suggesting the oral cavity might be a reservoir of this bacterium.

Evaluating and minimising social stress in the care of captive bottlenose dolphins (Tursiops aduncus)

AbstractStress can increase an organism’s susceptibility to disease. Thus, managing stress and its causes are important elements of captive care. Social factors such as changes in group dynamics, competition over resources, and unstable dominance hierarchies are potential stressors for highly social animals such as bottlenose dolphins (Tursiops sp). We present three case studies of mortality and illness in captive bottlenose dolphins and suggest that stress, resulting from social instability and ensuing aggressive interactions, is likely to have played a role in these health consequences. Stress is implicated by blood profiles, loss of appetite, and gastric ulcers, and social problems and instability are evident in the quantitative analysis of individual activity levels and association patterns. This is a unique study on marine mammals in that it demonstrates a correlation between quantitative behavioral indices and physiological measures of stress and health. Recommendations are made for the management of captive dolphins including regular quantitative assessment of behavior and associations and maintenance of appropriate groupings of age and sex classes. Behavioral records can be an important early indicator of health problems and may also serve as a useful tool for recognizing potentially stressful social changes and circumstances. Zoo Biol 21:5–26, 2002. © 2002 Wiley‐Liss, Inc.

Food intake and body measurements of Atlantic bottlenose dolphins ( Tursiops truncates) in captivity

The food consumption (recorded in kg of individual fish species), body length and mass of 11 Atlantic bottlenose dolphins kept first at Windsor Safari Park, UK (1979–1993/1994), and later at Harderwijk Marine Mammal Park, The Netherlands (1993/1994–1995) are reported. This broad-scale, longitudinal study is based on historical data that were originally recorded for short-term husbandry purposes. The chemical composition and caloric value of the diet were variable and were not recorded. The food intake quantities should therefore be viewed as rough weight estimates of what wild conspecifics might eat (depending on their diet). The average annual food consumption of adult males and non-pregnant, non-lactating females was approximately 2000 kg of fish (estimated at 176×10 5 kJ). Food consumption showed little increase during gestation, but was 58–97% higher during lactation than during similar periods in non-reproductive years. All six calves began to eat solid food within a year of birth although suckling continued for 14–37 months after birth. The pattern of food intake of mothers and calves varied substantially between suckling periods. No seasonal changes in food consumption were detected, although there were small seasonal changes in water temperature. Births occurred at various times of year, since the timing of mating varied between years. The animals' body length increased rapidly during the first 3 years of life after which the growth rate decreased. Body length reached asymptote at approximately 270 cm. Adults of both sexes weighed around 260 kg. The relationship between standard body length (in cm) and body mass (in kg), although based on a small sample size ( n=16), can be expressed as body mass=17.261e 0.0156(body length−100). Animals weighing 155–225 kg consumed between 2 and 4% of their body mass per day.

Animals, values and tourism — structural shifts in UK dolphin tourism provision

General concern for the environment within tourism practices does not guarantee that the rights and welfare of individual animals will be considered. Indeed, different philosophical positions: environmental ethics, animal welfare and animal rights would each have different implications if incorporated into tourism development. This paper reports on one case where the deliberate promotion of an animal rights perspective has brought about a structural transformation in tourism provision. In the UK, over the past ten years, there has been a complete shift away from viewing dolphins in captivity to viewing dolphins in the wild. This shift is illustrated with reference to the Morecambe Dolphin Campaign of 1989–1991, where animal rights activists brought about the closure of a dolphinarium through a combination of direct communication with tourists and through lobbying the licensing local authority. The different ethical issues associated with the UK's new wild dolphin watching infrastructure are illustrated with particular reference to the Moray Firth, Scotland. The importance of the tourism industry and tourism researchers recognising the significance of animals as individual actors is highlighted.

Is cetacean social learning unique?

Studies on captive dolphins have shown that they are capable of social learning. However, ethnographic data are less conclusive and many examples given for social learning can be explained in other ways. Before we can claim that cetacean culture is unique we need more rigorous studies which are fortunately not as difficult as Rendell and Whitehead seem to think.

Comprehension of signs by dolphins (Tursiops truncatus).

The authors assessed the ability of 6 captive dolphins (Tursiops truncatus) to comprehend without explicit training 3 human communicative signs (pointing, directed gaze, and replica). Pointing consisted of indicating the target item with the index finger and a fully extended arm. Directed gaze consisted of orienting the head and eyes toward the target item while the rest of the body remained stationary. The replica signal consisted of holding up an exact duplicate of the target item. On the initial series of 12 trials for each condition, 3 dolphins performed above chance on pointing, 2 on gaze, and none for replica. With additional trials, above chance performance increased to 4 dolphins for pointing, 6 for gazing, and 2 for replica. The replica sign seemed to be the most taxing for them (only 2 dolphins achieved results significantly above chance). Taken together, these results indicate that dolphins are able to interpret untrained communicative signs successfully.

Cardiac responses to acoustic playback experiments in the captive bottlenose dolphin (Tursiops truncatus).

Acoustic recordings were used to investigate the cardiac responses of a captive dolphin (Tursiops truncatus) to sound playback stimuli. A suction-cup hydrophone placed on the ventral midline of the dolphin produced a continuous heartbeat signal while the dolphin was submerged. Heartbeats were timed by applying a matched-filter to the phonocardiogram. Significant heart rate accelerations were observed in response to playback stimuli involving conspecific vocalizations compared with baseline rates or tank noise playbacks. This method documents that objective psychophysiological measures can be obtained for physically unrestrained cetaceans. In addition, the results are the 1st to show cardiac responses to acoustic stimuli from a cetacean at depth. Preliminary evidence suggests that the cardiac response patterns of dolphins are consistent with the physiological defense and startle responses in terrestrial mammals and birds.

Isolation and characterization of a Helicobacter sp. from the gastric mucosa of dolphins, Lagenorhynchus acutus and Delphinus delphis.

Gastric ulcerations in dolphins have been reported for decades. Some of these lesions were associated with parasitic infections. However, cases of nonparasitic gastric ulcers with no clearly defined etiology also have been reported in wild and captive dolphins. Considerable speculation exists as to whether dolphins have Helicobacter-associated gastritis and peptic ulcer disease. The stomachs of seven stranded Atlantic white-sided dolphins, Lagenorhynchus acutus, and 1 common dolphin, Delphinus delphis, were assessed for the presence of Helicobacter species. Novel Helicobacter species were identified by culture in the gastric mucosa of two of the eight dolphins studied and by PCR in seven of the eight dolphins. The gram-negative organisms were urease, catalase, and oxidase positive. Spiral to fusiform bacteria were detected in gastric mucosa by Warthin Starry staining. Histopathology revealed mild to moderate diffuse lymphoplasmacytic gastritis within the superficial mucosa of the main stomach. The pyloric stomach was less inflamed, and bacteria did not extend deep into the glands. The lesions parallel those observed in Helicobacter pylori-infected humans. Bacteria from two dolphins classified by 16S rRNA analysis clustered with gastric helicobacters and represent a novel Helicobacter sp. most closely related to H. pylori. These findings suggest that a novel Helicobacter sp. may play a role in the etiopathogenesis of gastritis and gastric ulcers in dolphins. To our knowledge this represents the first isolation and characterization of a novel Helicobacter sp. from a marine mammal and emphasizes the wide host distribution and pathogenic potential of this increasingly important genus.

Portable data acquisition system for EKG measurements in marine environments

In the present paper, an electronic prototype designed to acquire electrocardiographic signals from marine mammals has been developed. The system consists of a portable device that allows the on-line acquisition of EKG signals through a parallel port interface that is connected to a laptop computer. The EKG waveform, the voltage level, the bandwidth and the most relevant information from this type of signals is stored and analysed under real-time conditions by means of specifically implemented software. The whole system has been successfully tested to obtain the EKG from captive dolphins. The characteristics of the equipment presented here, with its low cost, size and energy requirements accomplish a portable system suitable for the acquisition of this type of signals in conductive media such as the seawater.

Concentrations of Progesterone in Milk from Bottlenose Dolphins during Different Reproductive States

There are few published reports of an alternative, less invasive method than blood sampling to obtain reproductive hormone concentrations from captive dolphins. The aims of this study were to: (1) validate milk as an effective alternative to blood plasma for determining progesterone concentrations; and (2) utilize milk samples collected frequently to obtain progesterone concentration profiles and determine reproductive status. During the course of this study 16 plasma/milk sample pairs were collected from four adult bottlenose dolphins to correlate plasma and milk concentrations of progesterone. Milk samples were also collected approximately weekly for 4–5 months during three independent lactational periods. Additionally, milk samples were collected daily for approximately 1 year during three other independent lactational periods. A highly significant correlation was found between progesterone concentrations in plasma and milk (r2=0.91, P<0.01). Progesterone contained in milk whey, fat, and solids were 3.95 ± 1.3, 8.5 ± 1.1, and 52.0 ± 0.6%, respectively. Progesterone profiles from milk samples collected from two dolphins during 1995 indicated pregnancies (with progesterone concentrations between 8 and 46.5 ng/ml) which resulted in parturition. High progesterone concentrations in a third dolphin that did not give birth indicated a possible pseudopregnancy or fetal resorption. A possible ovulation not resulting in pregnancy was evident in one female in 1998, follicular activity in another female in 1998, and a year-long anestrous period in the third animal studied in 1998. It is confirmed that dolphins can become pregnant while lactating and that the approximate time of conception is identifiable in milk profiles, illustrating the potential application of this method in pregnancy detection and reproductive monitoring.

Doing Business in Morally Troubled Waters

This essay argues that humans have not fully understood the cognitive and affective capacities of dolphins, and that we have mistakenly defended as morally acceptable practices that actually harm dolphins. In particular, this essay argues that the current use of hundreds of captive dolphins by Sea World and similar facilities in the entertainment industry is ethically indefensible. Focusing primarily on critical differences between humans and dolphins, this essay argues that central concepts like intelligence and language (which have played a critical role in discussions about whether dolphins have moral standing) should be seen as species-specific, not universal notions. As a result, there are insufficient grounds to make the traditional claim that dolphins' cognitive capacities place them on a significantly lower spot in the moral hierarchy than humans. This paper also claims that the full development of dolphin personalities may depend on the richness of social interaction that is common in the life of a dolphin in the wild. Consequently, dolphins can probably experience a greater degree of emotional pain or deprivation in captivity than has traditionally been thought.

Serum α- and γ-tocopherols, retinol, retinyl palmitate, and carotenoid concentrations in captive and free-ranging bottlenose dolphins ( Tursiops truncatus)

Concentrations of retinol, retinyl palmitate, β-carotene, α-carotene, cryptoxanthin, lutein, lycopene, α-tocopherol, and γ-tocopherol were measured in blood samples collected from 15 captive and 55 free-ranging bottlenose dolphins ( Tursiops truncatus). From June 1991 to June 1994, blood samples were collected from captive animals residing at two locations; at Seven Seas (Brookfield Zoo, Brookfield, IL) and Hawk’s Cay (Marathon Key, FL). Blood samples were collected from free-ranging animals from June 1991 to June 1996. Retinol levels were not significantly different between captive dolphin groups. However, Seven Seas animals had higher ( P<0.01) serum retinol concentrations compared to free-ranging animals (0.061 vs 0.041 μg/ml). Retinyl palmitate was not detected in the serum of captive or free-ranging dolphins. Alpha-tocopherol levels were significantly ( P<0.05) higher for Seven Seas dolphins (16.4 μg/ml) than for Hawk’s Cay (13.0 μg/ml) and free-ranging dolphins (12.5 μg/ml). Gamma-tocopherol concentrations were similar among captive and free-ranging dolphins. Free-ranging dolphins showed levels of circulating carotenoids (lutein and β-carotene) while the captive animals did not. Additional carotenoids (lycopene, α-carotene and cryptoxanthin) were analyzed but not detected in any samples. Serum vitamin differences between captive and free-ranging dolphins may reflect the natural diet or indicate some potential biological or nutritional status significance.

Whistle Convergence among Allied Male Bottlenose Dolphins (Delphinidae, Tursiops sp.)

Dolphins are adept at learning new vocalizations (whistles) throughout life, an ability thus far demonstrated in few nonhuman mammals. In dolphins, this ability is well documented in captivity but poorly studied in the wild, and little is known of its role in natural social behavior. This study documents the previously unknown phenomenon of whistle convergence among habituated free‐living male bottlenose dolphins (Tursiops sp.). Over a 4 yr study period, three male subjects formed an alliance, spending most of their time together and cooperating to herd females. Within individuals, whistle repertoires were more variable than expected based on previous studies, mostly performed with captive dolphins, but became less so during the course of the study. Among individuals, the distinctiveness of individual repertoires decreased such that the three males were virtually indistinguishable by the end of the study. Initially, some whistle types were shared. By the end of the study, the three males had formed a close alliance, and had all converged on one particular shared whistle form which they had rarely produced before forming the alliance. The results are discussed in terms of their implications for the prevailing ‘signature whistle’ hypothesis, as well as possible mechanisms and functional significance of whistle convergence among cooperating males.

Response to “Comments on ‘Broadband spectra of seismic survey air-gun emissions with reference to dolphin auditory thresholds’ ” [J. Acoust. Soc. Am. 105, 2047–2048 (1999)

In a prior paper, “Broadband spectra of seismic survey air-gun emissions with reference to dolphin auditory thresholds” [J. Acoust. Soc. Am. 103, 2177–2184 (1998)] a comparison was drawn between the estimation of sound levels at a distance which unconstrained dolphins would appear to maintain from a seismic air-gun source and the sound threshold at which captive dolphins displayed behavioral changes as reported by [Tech. Rpt. 1751, NCCOSC RDTE (1997)]. This prompted comments in the letter above on the validity of the conclusions of the prior paper. In this rebuttal, it is pointed out that uncertainties in the sound levels estimated in the prior paper arising from uncertainties in distance estimation, sound-propagation model, frequency weighting, and allowance for pulse duration are most unlikely to account for the very large difference of 48 dB between Goold and Fish’s results and Ridgway’s. The differences in criteria for deciding the threshold—behavior suggesting distress in captive dolphins (Ridgway et al.) and the assumption that dolphins swim to a distance at which the sound is tolerated (Goold and Fish), is the most likely explanation for the difference in the published figures.

Microsatellite diversity in captive bottlenose dolphins (Tursiops truncatus).

The utility of microsatellites for managing captive Tursiops truncatus was investigated. Specifically the level of genetic diversity among the loci examined and their usefulness for resolving paternity was assessed. Overall a relatively low level of genetic variation was found among captive dolphins. In addition, a high percentage of common alleles was found among dolphins belonging to different morphotypes (inshore versus offshore). The implications of these findings are discussed and suggestions are given for the use of genetic markers in captive propagation programs for T. truncatus.

Space and Behavior IN Captive Dolphins

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Haematological findings in captive dolphins and whales

To examine haematological features in five species of healthy, captive marine mammals. Twenty bottlenose dolphins (Tursips truncatus), seven Pacific white-sided dolphins (Lagenorhynchus obliquidens), five Risso dolphins (Grampus griseus) and five false killer whales (Pseudorca crassidens). The red blood cell count was 4.21 x 10(12)/L in bottlenose dolphins, 5.32 x 10(12)/L in Pacific white-sided dolphins, 4.35 x 10(12)/L in Risso dolphins and 4.43 x 10(12)/L in false killer whales. The haemoglobin concentration was 1.51 g/L and packed cell volume 44.7% in bottlenose dolphins; the corresponding values were 1.71 g/L and 48.9% in Pacific white-sided dolphins, 1.72 g/L and 49.4% in Risso dolphins, and 1.52 g/L and 47.8% in false killer whales. The white blood cell count was 7.097 x 10(9)/L in bottlenose dolphins, 5.928 x 10(9)/L in Pacific white-sided dolphins, 5.001 x 10(9)/L in Risso dolphins and 7.921 x 10(9)/L in false killer whales. There were no significant differences in these values among bottlenose dolphins and Pacific white-sided dolphins. The proportion of eosinophils in the differential leukocyte count ranged from 10.3% to 11.5% in bottlenose dolphins, Pacific white-sided dolphins and false killer whales, but was only 0.4% in Risso dolphins. The eosinophilic granules were larger in Risso dolphins and false killer whales than in bottlenose and Pacific white-sided dolphins.

Effect of Pool Features on the Behavior of Captive Dolphins

Marine Mammal ScienceVolume 13, Issue 3 p. 533-534 Effect of Pool Features on the Behavior of Captive Dolphins Kim Bassos-Hull, Kim Bassos-Hull Chicago Zoological Society, Conservation Biology Department, % Mote Marine Laboratory, 1600 Thompson Parkway, Sarasota, Florida 34236, U.S.A.Search for more papers by this authorRandall S. Wells, Randall S. Wells Chicago Zoological Society, Conservation Biology Department, % Mote Marine Laboratory, 1600 Thompson Parkway, Sarasota, Florida 34236, U.S.A.Search for more papers by this author Kim Bassos-Hull, Kim Bassos-Hull Chicago Zoological Society, Conservation Biology Department, % Mote Marine Laboratory, 1600 Thompson Parkway, Sarasota, Florida 34236, U.S.A.Search for more papers by this authorRandall S. Wells, Randall S. Wells Chicago Zoological Society, Conservation Biology Department, % Mote Marine Laboratory, 1600 Thompson Parkway, Sarasota, Florida 34236, U.S.A.Search for more papers by this author First published: 26 August 2006 https://doi.org/10.1111/j.1748-7692.1997.tb00665.xCitations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume13, Issue3July 1997Pages 533-534 RelatedInformation