Laterality of Eye Use by Bottlenose (Tursiops truncatus) and Rough-Toothed (Steno bredanensis) Dolphins While Viewing Predictable and Unpredictable Stimuli

Laterality of eye use has been increasingly studied in cetaceans. Research supports that many cetacean species keep prey on the right side while feeding and preferentially view unfamiliar objects with the right eye. In contrast, the left eye has been used more by calves while in close proximity to their mothers. Despite some discrepancies across and within species, laterality of eye use generally indicates functional specialization of brain hemispheres in cetaceans. The present study aimed to examine laterality of eye use in bottlenose dolphins (Tursiops truncatus) and rough-toothed dolphins (Steno bredanensis) under managed care. Subjects were video-recorded through an underwater window while viewing two different stimuli, one predictable and static and the other unpredictable and moving. Bottlenose dolphins displayed an overall right-eye preference, especially while viewing the unpredictable, moving stimulus. Rough-toothed dolphins did not display eye preference while viewing stimuli. No significant correlations between degree of laterality and behavioral interest in the stimuli were found. Only for bottlenose dolphins were the degree of laterality and curiosity ratings correlated. This study extends research on cetacean lateralization to a species not extensively examined and to stimuli that varied in movement and degree of predictability. Further research is needed to make conclusions regarding lateralization in cetaceans.

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Lateralized visual behavior in bottlenose dolphins (Tursiops truncatus) performing audio–visual tasks: The right visual field advantage

Behavioural Processes ◽

10.1016/j.beproc.2005.09.005 ◽

2006 ◽

Vol 71 (1) ◽

pp. 41-50 ◽

Cited By ~ 16

Author(s):

F. Delfour ◽

K. Marten

Keyword(s):

Visual Field ◽

Tursiops Truncatus ◽

Bottlenose Dolphins ◽

Right Visual Field ◽

Visual Behavior ◽

Visual Tasks ◽

The Right

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Behaviour reactions of bottlenose dolphins (Tursiops truncatus) to multirotor Unmanned Aerial Vehicles (UAVs)

Scientific Reports ◽

10.1038/s41598-019-44976-9 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 16

Author(s):

Ticiana Fettermann ◽

Lorenzo Fiori ◽

Martin Bader ◽

Ashray Doshi ◽

Dan Breen ◽

...

Keyword(s):

Unmanned Aerial Vehicles ◽

Tursiops Truncatus ◽

Bottlenose Dolphins ◽

Cost Effective ◽

Aerial Survey ◽

Cetacean Species ◽

Age Class ◽

Aerial Vehicles ◽

Vtol Uav ◽

Aerial Observation

Abstract Unmanned aerial vehicles (UAVs) represent a novel and cost effective research tool to investigate cetacean behaviour, as conventional aircraft are expensive, limited in the altitude they can fly at and potentially disturb sensitive wildlife. In addition, the aerial observation from the UAVs allows assessment of cetacean behaviour from an advantageous perspective and can collect high spatial and temporal resolution data, providing the opportunity to gather accurate data about group size, age class and subsurface behaviour. However, concerns have been raised about the potential risks of disturbance to animals caused by the UAV’s visual and acoustic stimuli. Boat-based surveys were conducted to assess the short-term behavioural responses of resting bottlenose dolphins (Tursiops truncatus) to a lightweight Vertical take-off and landing (VTOL) UAV flown at 10, 25, and 40 m altitude. Changes in group swim direction and frequencies of surface and aerial behavioural events were recorded from an anchored research vessel before (control) and during the aerial survey. The number of reorientation and tail slap events increased significantly between controls and flights when the UAV was flown at 10 m over the animals. In contrast, no significant differences were detected when the aircraft was flown at 25 and 40 m altitude. However, a precautionary approach is recommended for research applications requiring lower flight altitudes, with further research recommended to assess how different cetacean species and age class may respond to the UAV presence.

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Indication of lethal interactions between a solitary bottlenose dolphin (Tursiops truncatus) and harbor porpoises (Phocoena phocoena) in the German Baltic Sea

BMC Zoology ◽

10.1186/s40850-020-00061-7 ◽

2020 ◽

Vol 5 (1) ◽

Author(s):

Stephanie Gross ◽

Philip Claus ◽

Peter Wohlsein ◽

Tina Kesselring ◽

Jan Lakemeyer ◽

...

Keyword(s):

Baltic Sea ◽

Bottlenose Dolphin ◽

Tursiops Truncatus ◽

Bottlenose Dolphins ◽

Temporal Correlation ◽

First Record ◽

Phocoena Phocoena ◽

Cetacean Species ◽

The Baltic ◽

Harbor Porpoises

Abstract Background Aggressive interactions between bottlenose dolphins (Tursiops truncatus) and harbor porpoises (Phocoena phocoena) have been reported in different parts of the world since the late 1990s. In the Baltic Sea, harbor porpoises are the only native cetacean species, while bottlenose dolphins may appear there temporarily. In the fall of 2016, a solitary male photo-identified bottlenose dolphin stayed in the German Baltic Sea of Schleswig-Holstein for 3 months. During that time, the necropsies of the stranded harbor porpoises revealed types of trauma of varying degrees in six animals, which is unusual in this area. The purpose of this study was to determine if the appearance of the bottlenose dolphin could be linked to the trauma of the harbor porpoise carcasses. Results Pathological findings in these animals included subcutaneous, thoracic and abdominal hemorrhages, multiple, mainly bilateral, rib fractures, and one instance of lung laceration. These findings correspond with the previously reported dolphin-caused injuries in other regions. Moreover, public sighting reports showed a spatial and temporal correlation between the appearance of the dolphin and the stranding of fatally injured harbor porpoises. Conclusion Despite the fact that no attack has been witnessed in German waters to date, our findings indicate the first record of lethal interactions between a bottlenose dolphin and harbor porpoises in the German Baltic Sea. Furthermore, to our knowledge, this is the first report of porpoise aggression by a socially isolated bottlenose dolphin.

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Saliva and Blood Cortisol Measurement in Bottlenose Dolphins (Tursiops truncatus): Methodology, Application, and Limitations

Animals ◽

10.3390/ani12010022 ◽

2021 ◽

Vol 12 (1) ◽

pp. 22

Author(s):

Daniela Rickert ◽

Ralph Simon ◽

Lorenzo von Fersen ◽

Katrin Baumgartner ◽

Thomas Bertsch ◽

...

Keyword(s):

Animal Welfare ◽

Tursiops Truncatus ◽

Medical Training ◽

Bottlenose Dolphins ◽

Laboratory Method ◽

Blood Samples ◽

Saliva Cortisol ◽

Hair Samples ◽

Cortisol Levels ◽

The Right

A central task of zoos and aquaria is the frequent and accurate assessment of their animals’ welfare. Recently, important steps have been made, such as the introduction of animal welfare evaluation tools and welfare decision trees. To determine animal welfare, it is not only important to collect life history data, such as longevity and reproductive success, but also for experienced observers or caretakers to conduct behavioral observations on a regular basis to assess animals’ emotional state. To physiologically validate welfare observations, glucocorticoid levels are usually assessed, as they are a common indicator of stress. While, for many animals, these levels can be easily determined via fecal or hair samples, for cetaceans, the levels are usually determined via blood samples. As blood samples cannot be taken very frequently and the process may cause stress to the animals (if the samples are not taken following medical training), other techniques, such as the measurement of health biomarkers (especially cortisol, which can be measured in saliva), have become the focus of cetacean stress research. However, there are two problems associated with saliva measurements in cetaceans: saliva might either be diluted with pool water or be contaminated by fodder fish, as frozen fish usually contains high levels of cortisol. In our study, we investigated how saliva cortisol levels are connected to blood cortisol levels and how saliva cortisol can be influenced by fodder fish. We examined saliva and blood samples in eleven bottlenose dolphins (Tursiops truncatus) kept in an outdoor and indoor facility in Germany. Furthermore, we assessed the cortisol levels of different kinds of fodder fish. Our data show that, although saliva cortisol values are elevated under stress and arousal, they seem not to be correlated with blood cortisol values. We also show that, after feeding, saliva cortisol values are increased up to 100-fold. Our results suggest that saliva cortisol measurements in dolphins have to be conducted and considered with care, as they can easily be contaminated. Moreover, it is important to use the right laboratory method in order to specifically detect cortisol; in our study, we conducted reliable tests, using LC-MS/MS.

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Lateralized Behavior of Bottlenose Dolphins Using an Underwater Maze

International Journal of Comparative Psychology ◽

10.46867/ijcp.2016.29.00.19 ◽

2016 ◽

Vol 29 ◽

Cited By ~ 2

Author(s):

Fay E. Clark ◽

Stan A. Kuczaj II

Keyword(s):

Task Complexity ◽

Bottlenose Dolphins ◽

The Body ◽

Left Brain ◽

Wide Range ◽

Novel Objects ◽

Eye Preference ◽

The Right ◽

Familiar Stimuli ◽

The Brain

Behavior is lateralized when it is performed preferentially by one side of the body, and this phenomenon is seen across a wide range of vertebrate taxa. Furthermore the brain and body are contralateral in many animals, meaning that the left brain hemisphere most dominantly controls the right side of the body and vice versa. Lateralized behavior in humans and nonhuman primates reveals a population right-hand bias. Recent studies in primates have also begun to link differences in lateralized behavior to task complexity, and responses to novel versus familiar stimuli. Parallel research on cetaceans is sparse although evidence accrued over the last decade suggests captive dolphins have a preference for swimming counter-clockwise, a right-eye advantage in spatio-cognitive tasks and a right-eye preference for viewing novel objects, although this is the reverse of the general vertebrate pattern. Lateralized behavior was examined in a group of six male bottlenose dolphins (Tursiops truncatus) in response to a novel underwater maze, and compared to behavior during a baseline condition (no maze present). Dolphins were significantly more likely to swim counter-clockwise round their pool during both the baseline and maze condition, interpreted as a right eye bias. Swimming rotation was also weaker in dolphins during the maze condition, suggesting that the maze may have disrupted routine circular swimming behavior. There was no clear preference for using the left or right side of the maze, except in two high- using subjects with a strong right preference. Modifications and extensions to the methods are discussed.

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Nitrergic and Substance P Immunoreactive Neurons in the Enteric Nervous System of the Bottlenose Dolphin (Tursiops truncatus) Intestine

Animals ◽

10.3390/ani11041057 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1057

Author(s):

Cristiano Bombardi ◽

Anna Maria Rambaldi ◽

Giorgia Galiazzo ◽

Fiorella Giancola ◽

Jean-Marie Graïc ◽

...

Keyword(s):

Nervous System ◽

Substance P ◽

Enteric Nervous System ◽

Bottlenose Dolphin ◽

Tursiops Truncatus ◽

Bottlenose Dolphins ◽

Enteric Neurons ◽

Cetacean Species ◽

Intestinal Functions ◽

Oxide Synthase

Compared with other mammals, the digestive system of cetaceans presents some remarkable anatomical and physiological differences. However, the neurochemical features of the enteric nervous system (ENS) in these animals have only been described in part. The present study gives a description of the nitrergic and selected peptidergic systems in the myenteric plexus (MP) and submucosal plexus (SMP) of the intestine of the bottlenose dolphin (Tursiops truncatus). The distribution and morphology of neurons immunoreactive (IR) for the neuronal nitric oxide synthase (nNOS) and Substance P (SP) were immunohistochemically studied in formalin-fixed specimens from the healthy intestine of three animals, and the data were compared with those described in the literature on other mammals (human and non-human). In bottlenose dolphins, the percentages of nitrergic neurons (expressed as median and interquartile range—IQR) were 28% (IQR = 19–29) in the MP and 1% (IQR = 0–2) in the SMP, while the percentages of SP-IR neurons were 31% (IQR = 22–37) in the MP and 41% (IQR = 24–63) in the SMP. Although morphological features of nNOS- and SP-IR neurons were similar to those reported in other mammals, we found some noticeable differences in the percentages of enteric neurons. In fact, we detected a lower proportion of nNOS-IR neurons in the SMP and a higher proportion of SP-IR neurons in the MP compared to other mammals. To the best of the authors’ knowledge, this study represents the first description and quantification of nNOS-IR neurons and the first quantification of SP-IR neurons in the intestine of a cetacean species. As nNOS and SP are important mediators of intestinal functions and the nitrergic population is an important target for many neuroenteropathies, data obtained from a healthy intestine provide a necessary basis to further investigate and understand possible functional differences and motor intestinal dysfunctions/alterations in these special mammals.

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Biology and ecology of bottlenose dolphins (Tursiops truncatus) stranded and sighted at 25°S in the south-western Atlantic Ocean during 1989–2016

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315418000425 ◽

2018 ◽

Vol 98 (5) ◽

pp. 1129-1140

Author(s):

Camila Domit ◽

Isabela G. Domiciano ◽

Matt K. Broadhurst ◽

Ana Paula F. R. Bracarense ◽

Liana Rosa ◽

...

Keyword(s):

Atlantic Ocean ◽

Tursiops Truncatus ◽

Bottlenose Dolphins ◽

The South ◽

Cetacean Species ◽

Western Atlantic ◽

Western Atlantic Ocean ◽

Advanced Stages ◽

Spatio Temporal ◽

Future Work

Historical strandings and sightings (1989–2016) of Tursiops truncatus at 25oS in the south-western Atlantic Ocean (Paraná, Brazil) were assessed to (1) investigate temporal fluctuations; and (2) quantify biological, ecological and health parameters of regional populations. In total, 57 T. truncatus carcasses in mostly advanced stages of decomposition (~80% of all specimens) were recorded. Standardized temporal strandings (per observational effort) varied considerably and with no clear annual relationship beyond a peak in 2007, but there were consistently more strandings in winter/spring (74%) than summer/autumn (26%). While there was uncertainty over age estimation (i.e. not available for the population), individuals classified as juveniles/subadults were more frequent (80%) than calves (14%) and adults (6%). Of 28 carcasses assessed, 27 showed a positive linear relationship between TL and condyle-basal length, while one specimen had a clear southern skull morphotype. Suggestive lesions of Crassicauda sp. were recorded in 77% of assessed skulls and four types of tooth pathologies were observed. Nine individuals were more closely investigated for gross and histopathological alterations and had clear evidence of fishery interactions and various health issues associated with disease and oedema accompanied by alveolar fibrosis. While the regional frequency of T. truncatus strandings was lower than other more vulnerable cetaceans, the absolute numbers (e.g. 15 individuals in 2016) and some uncertainty concerning regional taxonomy are noteworthy, and justify ongoing spatio-temporal monitoring. Further, given the evidence of disease in some specimens, future work should not only encompass rigorous taxonomic assessments, but also health to comprehensively evaluate regional stocks. Small cetacean species are sentinels and their condition could inform ongoing environmental assessments.

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