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1
Wright, Katherine A. "Decreased ability to acquire food of a captive deaf dolphin (Tursiops truncatus): Slower reaction times and lower success rates." SURG Journal 4, no. 2 (March 11, 2011): 63–70. http://dx.doi.org/10.21083/surg.v4i2.1253.
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Oceanic anthropogenic noise, such as naval sonar, can cause temporary hearing loss in cetaceans, but it is not known to what extent hearing loss affects cetacean behaviours such as feeding. This study used a captive deaf Atlantic bottlenose dolphin (Tursiops truncatus) to test the hypothesis that hearing loss would decrease a dolphin’s ability to acquire food by preventing echolocation (using echoes to locate fish). Reaction time (time to acquire dropped fish) and success rate (percentage of successfully acquired fish) were measured for the deaf dolphin and for two dolphins with no known hearing disabilities at Dolphins Plus in Florida in May 2009. The deaf dolphin had a significantly slower mean reaction time and a significantly lower mean success rate than those of the two other dolphins. A hydrophone suggested that the deaf dolphin could not echolocate, and thus relied mainly on vision. The results illustrate that hearing loss can negatively affect a dolphin’s ability to acquire food. Therefore, sources and effects of dolphin hearing loss require further investigation in order to provide targets for anthropogenic noise levels.
2
Rossbach, Kelly A., and Denise L. Herzing. "Inshore and offshore bottlenose dolphin (Tursiops truncatus) communities distinguished by association patterns near Grand Bahama Island, Bahamas." Canadian Journal of Zoology 77, no. 4 (September 15, 1999): 581–92. http://dx.doi.org/10.1139/z99-018.
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Little is known about the behavior of offshore dolphin populations. Our purpose was to distinguish and describe stable social groups of bottlenose dolphins (Tursiops truncatus) between inshore and offshore West End, Grand Bahama Island (26°42'N, 79°00'W). Photoidentification was conducted from May to September, 1994 to 1996. A simple ratio index described association patterns between dolphins. Multidimensional scaling of association indices (n = 1711 dolphin pairs) distinguished two dolphin communities consisting of 28 dolphins (19 of known sex) found inshore and 15 dolphins (12 of known sex) found greater than or equal to 27 km offshore. Eight of the 15 offshore dolphins were opportunistically photographed in the same region between 1986 and 1990. The two communities were found at different water depths (Mann-Whitney U test, p < 0.01), over distinct bottom types (Kruskal-Wallis test, p < 0.01), and used different bottom-foraging strategies. Long-term site fidelity of up to 10 years and repeated dolphin associations of up to 8 years occurred greater than or equal to 27 km from shore. Dolphins sighted greater than or equal to 15 times averaged 48 associates (SD = 11, n = 28). A dolphin's closest associate was of the same gender 74% of the time. This study is the first to report long-term site fidelity and association patterns of bottlenose dolphins found far from shore.
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Platto, Sara, and Agathe Serres. "A Quantitative Assessment of Trainers-Dolphins’ Interactions in the Absence of Food Reward." Animals 13, no. 10 (May 16, 2023): 1651. http://dx.doi.org/10.3390/ani13101651.
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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.
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Rossi-Santos, Marcos R., Leonardo L. Wedekin, and Emygdio L. A. Monteiro-Filho. "Residence and site fidelity of Sotalia guianensis in the Caravelas River Estuary, eastern Brazil." Journal of the Marine Biological Association of the United Kingdom 87, no. 1 (February 2007): 207–12. http://dx.doi.org/10.1017/s0025315407055683.
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Between April 2002 and April 2005, 210 estuarine dolphin groups were sighted, with 58 animals individually identified. Fifteen dolphins were photo-identified just once, while only two animals were sighted in 15 different months. Some individuals showed long-term residence (more than 3 y). Residence rates showed heterogeneity in the dolphin's permanence of the estuary, with 60% of the individuals with low numbers (<10) and only 7% showing high values for residence (maximum=45.9). Continued resightings of some dolphins support the regular use of the study area by the animals, despite some individuals that, after a long time without resightings were registered again. Individual range analysis showed that dolphins shared the same common area, the Caravelas River Estuary. A marked fluctuation in the number of photo-identified dolphins was observed in the study area, revealed by the high number of individuals with just a few resightings. The majority of the dolphins (60%) present a yearly residence pattern, as observed in other areas, suggesting that a few individuals show high fidelity for the area, while many other dolphins move constantly between different areas for unknown reasons.
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Degrati, Mariana, Silvana L. Dans, Griselda V. Garaffo, and Enrique A. Crespo. "Seabird and dolphin associations: do seabirds benefit from feeding in association with dusky dolphins in Patagonia?" Journal of the Marine Biological Association of the United Kingdom 94, no. 6 (August 7, 2013): 1147–53. http://dx.doi.org/10.1017/s0025315413000945.
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The objective of this study was to describe associations between several species of seabirds and dusky dolphins. We investigated during what dolphin activities seabirds were most commonly associated, and the size of flock in relation to the number of dolphins in a group. Since both seabirds and dolphins may display different feeding strategies, we also investigated if benefits differed among seabird species. Data were collected in Golfo Nuevo (42°20′S65°00′W) on-board a research vessel between 2001 and 2008. A total of 224 mixed groups of seabirds were encountered during this study. The seabird–dolphin associations were mainly observed during dusky dolphin surface feeding. Shearwaters and kelp gulls were mainly observed in flocks that were associated with dolphins, while Magellanic penguins and cormorants were mainly observed without dolphins. Seabirds may be conditioned to the foraging strategy of dolphins, since birds are associated with dolphins only during dolphin surface feeding. This association probably helped seabirds to find prey, but there were no obvious benefits to dolphins.
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Park, Nam Kyu, and Yohan An. "Estimation of LNG Dolphin Capacity: Dolphins of Different Size in Republic of Korea." Journal of Marine Science and Engineering 10, no. 12 (December 19, 2022): 2031. http://dx.doi.org/10.3390/jmse10122031.
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The LNG terminals are characterized by a large number of ships entering the port during the winter season due to the seasonality of rapidly increasing demand for heating. In winter, there is a shortage of dolphin jetty wharf (dolphins), which increases the waiting rate for ships. Therefore, there is a practical argument that dolphins should be additionally built to solve the ship standby problem. This study proposes the proper LNG handling capacity of a terminal with multiple dolphins of different size. Studies on calculating the LNG handling capacity of LNG terminal dolphins have been proposed by UNCTAD and Ministry of Transport of China (MTC). The formula-based calculation of LNG handling capacity has the advantage of being simple, but it has the disadvantage of not reflecting the actual operation. In this study, the proper LNG handling capacity is measured using a simulation method to overcome the limitations of formula-based calculation for Incheon port in South Korea. In order to check whether the method by simulation is justified, it is compared with the unloading capacity by the calculation formula. This study finds that the proper (or optimal) LNG handling capacity of Incheon port is determined by a dolphin occupancy of 49%, where the dolphin’s profits are maximized. As the results of simulation model, the proper (or optimal) loading capacity is 38.5 million m3 when dolphin occupancy is 49%. The capacity of individual dolphin is estimated at 17.0 million m3 for 70,000 DWT dolphin and 21.2 million m3 for 120,000 DWT dolphin, respectively. The main points of this study to use simulation model are as follows: First, the number of non-working days should be considered. Second, the optimal dolphin occupancy should be determined by finding the maximum profit point of using the pier. Third, if the size of the dolphin is different, an appropriate simulation will be implemented. Fourth, the data of the peak season should be analyzed. Finally, it should be checked whether the ship waiting rate is acceptable level or not.
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Martha Purwahita, Anak Agung Ayu Ribeka, Anak Agung Sagung Srikandi, I. Gusti Agung Budiasih, and I. Wayan Arka. "WISATA LUMBA-LUMBA DI PANTAI LOVINA DESA KALIBUKBUK, KABUPATEN BULELENG (STUDI KASUS ATRAKSI LUMBA-LUMBA DI HOTEL MELKA)." Forum Manajemen 20, no. 2 (August 23, 2022): 99–107. http://dx.doi.org/10.61938/fm.v20i2.481.
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Dolphin tourist attraction at Lovina Beach is one of the attractions to see dolphins on the high seas which is able to attract tourists to visit, as well as being a tourist attraction in North Bali. The development of dolphin tourism attractions has been shown in the swimming pool, but the survival of the dolphins is threatened. This case study discusses the exploitation of dolphins at the Melka Excelsior Hotel. This study aims to identify and analyze problems related to the exploitation of dolphins. Dolphin tourism attractions have positive and negative impacts and follow-up is needed to enjoy safe and comfortable dolphin tourism, especially dolphin conservation. The research method used is the field observation method and literature study obtained from journals and the internet. The placement of dolphins in the pond due to conditions that are not in accordance with their natural habitat will have a direct impact on these mammals. The activity of this dolphin attraction is more directed towards exploitation so that the need for dolphin conservation for commercial purposes does not have a positive effect on the dolphins themselves and lacks attention to these mammals.
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Mujiyanto, Mujiyanto, Riswanto Riswanto, Dharmadi Dharmadi, and Wildan Ghiffary. "COMPOSITION AND DISTRIBUTION OF DOLPHIN IN SAVU SEA NATIONAL MARINE PARK, EAST NUSA TENGGARA." Indonesian Fisheries Research Journal 23, no. 2 (February 12, 2018): 55. http://dx.doi.org/10.15578/ifrj.23.2.2017.55-67.
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Dolphins are one of the most interesting cetacean types included in family Delphinidae or known as the oceanic dolphins from genus Stenella sp. and Tursiops sp. Migration and abundance of dolphins are affected by the presence of food and oceanographic conditions. The purpose of this research is to determine the composition and distribution of dolphins in relation to the water quality parameters. Benefits of this research are expected to provide information on the relationship between distributions of the family Delphinidae cetacean (oceanic dolphins) and oceanographic conditions. The method for this research is descriptive exploratory, with models onboard tracking survey. Field observations were done in November 2015 and period of March-April 2016 outside and inside Savu Sea National Marine Park waters. The sighting of dolphin in November and March-April found as much seven species: bottlenose dolphin, fraser’s dolphin, pantropical spotted dolphin, risso’s dolphin, rough-toothed dolphin, spinner dolphin and stripped dolphin. The highest species distribution noted in the Savu Sea is spinner dolphin, pantropical spotted dolphin, rough-toothed dolphin and frazer’s dolphin. The existence of dolphins in Savu Sea is more related with sea surface temperature than others oceanographic parameters. This condition is suspected due to the influence of sea surface temperature to body temperature of dolphin especially for foraging activities. The habit of dolphin is more active around Sumba Island and Daratan Timor waters while in the evening the animal is usually going to Manggarai and Rote Ndao Islands waters to rest.
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Branstetter, Brian K., Rachel Brietenstein, Gavin Goya, Megan Tormey, Teri Wu, and James J. Finneran. "Spatial acuity of the bottlenose dolphin (Tursiops truncatus) biosonar system with a bat and human comparison." Journal of the Acoustical Society of America 151, no. 6 (June 2022): 3847–57. http://dx.doi.org/10.1121/10.0011676.
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Horizontal angular resolution was measured in two bottlenose dolphins using a two-alternative forced-choice, biosonar target discrimination paradigm. The task required a stationary dolphin positioned in a hoop to discriminate two physical targets at a range of 4 m. The angle separating the targets was manipulated to estimate an angular discrimination threshold of 1.5°. In a second experiment, a similar two-target biosonar discrimination task was conducted with one free-swimming dolphin, to test whether its emission beam was a critical factor in discriminating the targets. The spatial separation between two targets was manipulated to measure a discrimination threshold of 6.7 cm. There was a relationship between differences in acoustic signals received at each target and the dolphin's performance. The results of the angular resolution experiment were in good agreement with measures of the minimum audible angle of both dolphins and humans and remarkably similar to measures of angular difference discrimination in echolocating dolphins, bats, and humans. The results suggest that horizontal auditory spatial acuity may be a common feature of the mammalian auditory system rather than a specialized feature exclusive to echolocating auditory predators.
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Avila, Isabel Cristina, Carolina Garcia, and Juan Carlos Bastidas. "A note on the use of dolphins as bait in the artisanal fisheries off Bahía Solano, Chocó, Colombia." J. Cetacean Res. Manage. 10, no. 2 (February 15, 2023): 179–82. http://dx.doi.org/10.47536/jcrm.v10i2.652.
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Dolphin hunting for fishing bait in Bahía Solano, Chocó, Colombia, was evaluated during eight months, between July 2005 and April 2006. Interviews were conducted with 122 fishermen (18.2% of the registered fishermen in the zone), who cover at most 890km2 when fishing (approximately 2.3% of the Pacific Territorial Sea of Colombia), and data obtained from landings at a fishing company. Only fishermen using longlines (37.3%) confirmed using dolphins as bait. It was not possible to obtain additional information about date, specific location or dolphin species, but the most probable captured species were common bottlenose dolphin and pantropical spotted dolphin. Nine dolphins were killed during the study period (1.1 dolphins/month) and extrapolating these numbers to all fishermen using longlines in the region (250), 24 dolphins might have been taken during the study period (3 dolphins/month). Fish species caught using dolphin bait include Pacific bearded brotula, groupers and smooth-hound.
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Kreiviniene, Brigita, Laura Lupeikaitė, Aelita Bredelytė, and Žilvinas Kleiva. "DOLPHIN ASSISTED THERAPY: WELFARE OF BOTH PATIENTS WITH DEPRESSION AND PARTICIPATING DOLPHINS." SOCIETY. INTEGRATION. EDUCATION. Proceedings of the International Scientific Conference 2 (May 22, 2024): 575–92. http://dx.doi.org/10.17770/sie2024vol2.7829.
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The main aim of this research was to measure the effect of dolphin assisted therapy on both patients and participating dolphins. The research measured welfare of patients with depression and situational welfare of dolphins which participated in the dolphin assisted therapy programme. Patients with organic depression took part in two-week dolphin assisted therapy sessions. When measuring situational welfare of dolphins, the study sample consisted of nine individual dolphins (Tursiops truncatus ponticus, Lat.): three males and six females ranging from five to twenty years. The main research results revealed that psychosocial characteristics of patients with organic depression disorder as well as patients’ self-evaluation changed statistically significantly, the symptoms of depression decreased. The research revealed that patients were much more physically active during the period of participation in the dolphin assisted therapy process than before. The analysis of dolphin behaviour brought to the light that most of the therapy time dolphins behaved positively. There were noticed no therapy sessions where the dolphin behaviour would be evaluated as more negative than positive or just negative.
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Ryabov, V. A. "Hydroacoustical regularities of food behavior of dolphins." Marine Biological Journal 3, no. 2 (June 29, 2018): 81–97. http://dx.doi.org/10.21072/mbj.2018.03.2.07.
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Hydroacoustic regularities of food behavior of dolphins are determined by characteristics and functionality of their acoustic signals. All the acoustic signals of dolphins are classified depending on their physical characteristics by the theory of signals and echolocation as follows: sequences of ultrashort ultrawideband coherent pulses – ‘clicks’, frequency-modulated (FM) simultones with uniformly distributed tones – ‘whistles’, packets of mutually coherent pulses (CI), packets of mutually noncoherent pulses (NI) and packets of versatile pulses (VI). They play the role of probing signals of six dolphin sonars optimized for solving various echolocation tasks. The possibilities of using the signals by dolphins in searching and classifying food objects by echolocation have been studied in this work on the basis of both experimental data obtained by the researcher and those available in literature. The dolphins can use sequences of ‘clicks’ to detect food objects (individual fish at the distance up to 70–110 m, a school of fish at the distance up to 450–600 m) and conspecifics (dolphins) (at the distance up to 450–600 m) and to classify food objects. The dolphins can use ‘whistles’ to detect food objects (individual fish at the distance up to 2 km, a school of fish at the distance up to 9–13 km) and conspecifics (dolphins) (at the distance up to 9–13 km) and to determine their range and relative radial velocity. ‘Whistles’ provide higher accuracy and the range of echolocation of food objects and conspecifics compared to ‘clicks’ (by more than an order of magnitude). Furthermore, the FM sonar provides the measure of the radial velocity of approaching or distance removing of underwater object to or from a dolphin. However, an acute analysis of the amplitude-time regularities of the fish echo for the purpose of their classification is the advantage of sonar using ‘clicks’. The dolphins can use the packs of CI at the distances shorter than 2.5 m for tracing the position dynamics of the prey aiming at accurate capture. The high hearing resolution of the dolphin in time is about 0.02 ms; it allows processing the subtle temporal dynamics of the echoes. Packs of NI (signals of spoken language) can be used by dolphins to organize various types of association and complex cooperation between themselves when hunting and catching fish. Packets of VI can be used by dolphins to expand the echolocation of the survey area around the dolphin in order to improve the quality of food objects monitoring, regardless of the position of the dolphin’s head, as well as to determine the range, relative radial velocity and class of food objects, at short distances. Evolution and perfection of various types of acoustic signals, sonars and various methods of processing echo signals in dolphins is caused, first of all, by optimization of hydroacoustic regularities of their food behavior, along with the need for orientation in three-dimensional space. One can assume the presence of similar hydroacoustic regularities of food behavior in Odontoceti based on the similarity of their acoustic signals and morphology. The acoustic regularities of food behavior of dolphins and bats are similar, despite the fact that they have different habitats (water and terrestrial-air), and these mammals belong to different orders of the animal kingdom (Сetacea and Chiroptera).
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Ridgway, Sam, Dianna Samuelson Dibble, and Mark Baird. "Sights and sounds dolphins, Tursiops truncatus preying on native fish of San Diego Bay and offshore in the Pacific Ocean." PLOS ONE 17, no. 8 (August 17, 2022): e0265382. http://dx.doi.org/10.1371/journal.pone.0265382.
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For the first time, dolphins wearing video cameras were observed capturing and eating live native fish. While freely swimming in San Diego Bay, one dolphin caught 69 resident fish, 64 demersal, 5 near surface, while the other caught 40, 36 demersal and 4 near the surface. Two other dolphins were observed capturing 135 live native fish in a sea water pool. Two additional dolphins were observed feeding opportunistically during open water sessions in the Pacific Ocean. Notably, one of these dolphins was observed to consume 8 yellow-bellied sea snakes (Hydrophis platurus). Searching dolphins clicked at intervals of 20 to 50 ms. On approaching prey, click intervals shorten into a terminal buzz and then a squeal. Squeals were bursts of clicks that varied in duration, peak frequency, and amplitude. Squeals continued as the dolphin seized, manipulated and swallowed the prey. If fish escaped, the dolphin continued the chase and sonar clicks were heard less often than the continuous terminal buzz and squeal. During captures, the dolphins’ lips flared to reveal nearly all of the teeth. The throat expanded outward. Fish continued escape swimming even as they entered the dolphins’ mouth, yet the dolphin appeared to suck the fish right down.
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Mills, Eliza M. M., Sarah Piwetz, and Dara N. Orbach. "Vessels Disturb Bottlenose Dolphin Behavior and Movement in an Active Ship Channel." Animals 13, no. 22 (November 8, 2023): 3441. http://dx.doi.org/10.3390/ani13223441.
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Although the Port of Corpus Christi, Texas, has become a top oil exporter, it is unknown if local dolphins are disturbed by high year-round vessel traffic. A shore-based digital theodolite and automatic identification system receiver were used to record data to assess common bottlenose dolphin (Tursiops truncatus) behavioral states and movement patterns in the Corpus Christi Ship Channel (CCSC) in relation to vessel traffic. Multinomial logistic regression and generalized additive models were applied to analyze the data. Vessels were present within 300 m of dolphins during 80% of dolphin observations. Dolphins frequently foraged (40%), traveled (24%), socialized (15%), and milled (14%), but rarely oriented against the current (7%) or rested (1% of observations). Season, time of day, group size, vessel type, vessel size, and number of vessels were significant predictors of dolphin behavioral state. Significant predictors of dolphin movement patterns included season, time of day, group size, calf presence, vessel type, and vessel numbers. The CCSC is an important foraging area for dolphins, yet the high level of industrial activity puts the dolphins at risk of human-related disturbance and injury. There is a crucial need to monitor the impact of increased anthropogenic influences on federally protected dolphins in the active CCSC, with broad application to dolphins in other ports.
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Cuvertoret-Sanz, M., C. López-Figueroa, A. O’Byrne, A. Canturri, B. Martí-Garcia, E. Pintado, L. Pérez, et al. "Causes of cetacean stranding and death on the Catalonian coast (western Mediterranean Sea), 2012-2019." Diseases of Aquatic Organisms 142 (December 17, 2020): 239–53. http://dx.doi.org/10.3354/dao03550.
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The causes of cetacean stranding and death along the Catalan coast between 2012 and 2019 were systematically investigated. Necropsies and detailed pathological investigations were performed on 89 well-preserved stranded cetaceans, including 72 striped dolphins Stenella coeruleoalba, 9 Risso’s dolphins Grampus griseus, 5 bottlenose dolphins Tursiops truncatus, 1 common dolphin Delphinus delphis, 1 Cuvier’s beaked whale Ziphius cavirostris and 1 fin whale Balaenoptera physalus. The cause of death was determined for 89.9% of the stranded cetaceans. Fisheries interaction was the most frequent cause of death in striped dolphins (27.8%) and bottlenose dolphins (60%). Cetacean morbillivirus (CeMV) was detected on the Catalan coast from 2016 to 2017, causing systemic disease and death in 8 of the 72 (11.1%) striped dolphins. Chronic CeMV infection of the central nervous system was observed from 2018-2019 in a further 5 striped dolphins. Thus, acute and chronic CeMV disease caused mortality in 18% of striped dolphins and 14.6% of all 89 cetaceans. Brucella ceti was isolated in 6 striped dolphins and 1 bottlenose dolphin with typical brucellosis lesions and in 1 striped dolphin with systemic CeMV. Sinusitis due to severe infestation by the nematode parasite Crassicauda grampicola caused the death of 4 out of 6 adult Risso’s dolphins. Maternal separation, in some cases complicated with septicemia, was a frequent cause of death in 13 of 14 calves. Other less common causes of death were encephalomalacia of unknown origin, septicemia, peritonitis due to gastric perforation by parasites and hepatitis caused by Sarcocystis spp.
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Finn, Hugh, Rebecca Donaldson, and Michael Calver. "Feeding Flipper: a case study of a humandolphin interaction." Pacific Conservation Biology 14, no. 3 (2008): 215. http://dx.doi.org/10.1071/pc080215.
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We document a human-dolphin interaction involving the illegal feeding of wild Bottlenose Dolphins (Tursiops sp.) in Cockburn Sound, Western Australia from 1993-2003. In 1993 only one dolphin was considered conditioned to human interaction through food reinforcement. By 2001, 16% (n = 12) of the resident community of 74 adult dolphins were conditioned, and at least 14 dolphins were conditioned by 2003. Of the 13 conditioned dolphins of known sex, 11 (85%) were males. We observed conditioned dolphins initiating interactions by approaching recreational fishing boats and by residing for several hours at boat ramps and shore-based fishing sites. We only observed recreational fishers feeding dolphins, although anecdotal reports indicated additional feeding sources. We used belt transects to determine the densities of recreational boats and encounter rates for conditioned dolphins across habitats within Cockburn Sound. Encounter rates and boat densities were positively correlated, suggesting an association between recreational boat density and the ranging patterns of conditioned dolphins. This study demonstrates how illegal feeding interactions can intensify over time to affect a potentially biologically significant proportion of a local dolphin population. This emphasizes the need for early and pro-active intervention and demonstrates the value of longitudinal, individual-specific wildlife studies.
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Bonsembiante, Federico, Carlo Guglielmini, Michele Berlanda, Pietro Fiocco, Barbara Biancani, Carla Genovese, Silvia Bedin, and Maria Elena Gelain. "Biological Variation and Reference Change Value of Routine Hematology Measurands in a Population of Managed Bottlenose Dolphins (Tursiops truncatus)." Animals 13, no. 8 (April 11, 2023): 1313. http://dx.doi.org/10.3390/ani13081313.
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Hematological analyses are particularly useful in assessing a dolphin’s health status. However, the creation of appropriate reference intervals for this species is difficult due to the low number of reference individuals. The implementation of individual reference intervals (iRIs) allows researchers to overcome this limitation and, moreover, also consider the within-individual variability. The aims of this study were (1) to evaluate the biological variations in some hematological measurands, including erythrocytes (RBC), hematocrit (Hct), mean cellular volume and hemoglobin content (MCV and MCHC, respectively), RBC distribution width (RDW), leukocytes (WBC), and platelets (PLT); and (2) to calculate the index of individuality (IoI) and reference change value (RCV), which enable the production of iRIs, in healthy managed bottlenose dolphins. Seven dolphins were included, and the results of six hematological exams were analyzed for each animal. Analytical imprecision (CVa), within-dolphin variation (CVi), and between-dolphins variations (CVg) were calculated, and the IoI and RCV were derived for each measurand. All the hematological measurands had intermediate IoI except WBC, for which Iol was low. The calculated RCV ranged from 10.33% (MCV) to 186.51% (WBC). The results reveal that the majority of hematological measurands have an intermediate level of individuality in dolphins, and thus the application of iRIs is appropriate. The calculated RCV can also be applied to other managed dolphins and could be useful in interpreting serial CBC exams.
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Colbert, A., M. Stoskopf, C. Brownie, G. I. Scott, and J. Levine. "Anatomic site and interanimal variability in morphologic characteristics of bottlenose dolphin (Tursiops truncatus) skin likely to affect dermal absorption studies." American Journal of Veterinary Research 59, no. 11 (November 1, 1998): 1398. http://dx.doi.org/10.2460/ajvr.1998.59.11.1398.
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Abstract Objective To investigate anatomic site and interanimal variability in dolphin skin for use in development of models for cutaneous absorption studies. Sample Population Skin from 30 healthy free-ranging bottlenose dolphins (17 males and 13 females grouped by age) and 10 captive males between 13 and 19 years old. Procedure Biopsy specimens were collected from the 10 male dolphins at 3 anatomic sites and from the 30 dolphins at 1 site; specimens were evaluated by light microscopy. Stratum externum thickness, minimal depth to the vasculature, and maximal epidermal depth were measured at 4 locations on 4 sequential sections. Comparisons of replicate measurements for 3 skin characteristics were made within and among anatomic sites, between dolphins of the same sex and approximate age, and across males and females of various ages. Results The stratum externum in male dolphins was thicker. Differences attributable to age and anatomic site were not significant. Variation attributable to differences in stratum externum thickness between dolphins was significant. Differences among body sites within the same dolphin were significant but were not consistent from dolphin to dolphin. Mean stratum externum thickness was not different between males of the 2 cohorts, but mean maximal epidermal depth and mean minimal depth to the vasculature were different. Variances within the 2 male cohorts were not significantly different. Conclusions Studies affected by stratum externum thickness should eliminate the effect attributable to sex difference by using dolphins of the same sex or grouping analytical data by sex. Precision could be improved without increasing the total number of dolphins by collecting more than 1 sample/dolphin. (Am J Vet Res 1998;59:1398–1403)
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Bazúa-Durán, Carmen. "Differences in the whistle characteristics and repertoire of Bottlenose and Spinner Dolphins." Anais da Academia Brasileira de Ciências 76, no. 2 (June 2004): 386–92. http://dx.doi.org/10.1590/s0001-37652004000200030.
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Several methods have been used to compare the whistles produced by dolphins. The two methods used in this study are: (1) a classification of whistle contours in six categories (i.e. constant frequency, upsweep, downsweep, concave, convex, and sine) and (2) the extraction of frequency and time parameters from each whistle contour. Bottlenose Dolphin Tursiops truncatus whistles are described in the same way when comparing whistle contour distributions in each of the six categories and whistle frequency and time parameters using Discriminant Function Analysis. For Spinner Dolphin Stenella longirostris whistles, each method describes whistles differently. Several facts may explain these differences in describing dolphin whistles, such as a greater fluidity of Spinner Dolphin groups when compared to Bottlenose Dolphin groups, greater geographic variation in the whistles of Bottlenose Dolphins than in those of Spinner Dolphins, an average beginning frequency 16% lower than the average ending frequency in Spinner Dolphin whistles compared to a varied relationship for Bottlenose Dolphins, and stricter criteria used to define whistle contour categories in the study of Spinner Dolphin whistles than in the Bottlenose Dolphin whistle study.
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Donnelly, Roarke E., Alex Prots, and Christl A. Donnelly. "Better educational signage could reduce disturbance of resting dolphins." PLOS ONE 16, no. 4 (April 2, 2021): e0248732. http://dx.doi.org/10.1371/journal.pone.0248732.
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Spinner dolphins on Hawai‘i Island’s west coast (Stenella longirostris longirostris) rest by day in protected bays that are increasingly popular for recreation. Because more frequent interactions of people with these dolphins is likely to reduce rest for dolphins and to explain recent decline in dolphin abundance, the National Oceanic and Atmospheric Administration (NOAA) proposed stricter rules regarding interactions with spinner dolphins near the main Hawaiian Islands and plans to increase enforcement. Simultaneous investment in public education about both interaction rules and their biological rationale has been and is likely to be relatively low. To test the hypothesis that more educational signage will reduce human-generated disturbance of dolphins, a paper questionnaire was distributed to 351 land-based, mostly unguided visitors at three dolphin resting bays on Hawai‘i Island’s west coast. Responses indicated that visitors wanted to see dolphins, were ignorant of interaction rules, were likely to read signs explaining rules and their biological rationales, and were likely to follow known rules. Therefore, investment in effective educational signage at dolphin resting bays is recommended as one way to support conservation of spinner dolphins on Hawai‘i Island’s west coast and similar sites in the Hawaiian archipelago.
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Miller, LJ, J. Mellen, T. Greer, and SA Kuczaj II. "The effects of education programmes on Atlantic bottlenose dolphin (Tursiops truncatus) behaviour." Animal Welfare 20, no. 2 (May 2011): 159–72. http://dx.doi.org/10.1017/s0962728600002645.
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AbstractAtlantic bottlenose dolphins (Tursiops trucatus) are found in zoos and aquaria throughout the world. As the number of facilities with dolphin shows and interaction programmes increases, it becomes more important to understand the effects of such programmes on dolphin behaviour. The present study examined the short-term effects of dolphin shows and interaction programmes on the behaviour of Atlantic bottlenose dolphins at six facilities. Rates of affiliative behaviour, aggressive behaviour, repetitive behaviour and percentage of time spent socialising were found to be unrelated to dolphin shows or interaction programmes. Additionally, dolphins exhibited higher rates of behavioural diversity, diversity of swimming style, and play behaviour following shows and interaction programmes. These results suggest that dolphin shows and interaction programmes can be an important part of an enrichment programme for dolphins in zoological institutions. However, individual differences should be considered when animals participate in these types of programmes.
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Alam, Shayer Mahmood Ibney, Md Muzammel Hossain, Mohammad Abdul Baki, and Naser Ahmed Bhouiyan. "Status of ganges dolphin, Platanista gangetica gangetica (Roxburgh, 1801) in the river Buriganga, Dhaka." Bangladesh Journal of Zoology 43, no. 1 (December 29, 2015): 109–20. http://dx.doi.org/10.3329/bjz.v43i1.26143.
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Population abundance and density of the Ganges River Dolphin Platanista gangetica gangetica (Roxburgh, 1801) was studied in the Buriganga River from December 2012 to November 2013.The survey was conducted twice a month. The dolphins were counted directly and applied in transect length of 10.5 km within 15 km stretches of the river. A total of 34 sightings of dolphins were recorded both in individuals and groups. We encountered the dolphins at the rate of 0.48 dolphins per km in the Buriganga River. Highest best-high-low estimate of 12-14-10 individuals were recorded in November 2013. The mean density was 0.38 (SD ±0.37) dolphins/km² with the highest density of dolphin observed also in the month of November, which was 1.14 dolphin/km². Pollution and water traffic were observed to be the major threats to the dolphins.Bangladesh J. Zool. 43(1): 109-120, 2015
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Christman, Katie A., James J. Finneran, Jason Mulsow, Dorian S. Houser, and Timothy Q. Gentner. "The effects of range and echo-phase on range resolution in bottlenose dolphins (Tursiops truncatus) performing a successive comparison task." Journal of the Acoustical Society of America 155, no. 1 (January 1, 2024): 274–83. http://dx.doi.org/10.1121/10.0024342.
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Echolocating bats and dolphins use biosonar to determine target range, but differences in range discrimination thresholds have been reported for the two species. Whether these differences represent a true difference in their sensory system capability is unknown. Here, the dolphin's range discrimination threshold as a function of absolute range and echo-phase was investigated. Using phantom echoes, the dolphins were trained to echo-inspect two simulated targets and indicate the closer target by pressing a paddle. One target was presented at a time, requiring the dolphin to hold the initial range in memory as they compared it to the second target. Range was simulated by manipulating echo-delay while the received echo levels, relative to the dolphins' clicks, were held constant. Range discrimination thresholds were determined at seven different ranges from 1.75 to 20 m. In contrast to bats, range discrimination thresholds increased from 4 to 75 cm, across the entire ranges tested. To investigate the acoustic features used more directly, discrimination thresholds were determined when the echo was given a random phase shift (±180°). Results for the constant-phase versus the random-phase echo were quantitatively similar, suggesting that dolphins used the envelope of the echo waveform to determine the difference in range.
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Olson, Grace L., Stephanie H. Stack, Abigail F. Machernis, Florence A. Sullivan, and Jens J. Currie. "Mapping the Exposure of Pantropical Spotted Dolphins and Common Bottlenose Dolphins to Different Categories of Vessel Traffic in Maui Nui, Hawai‘i." Aquatic Mammals 48, no. 2 (March 15, 2022): 167–81. http://dx.doi.org/10.1578/am.48.2.2022.167.
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The increase and diversification of vessel traffic worldwide has resulted in a variety of known disturbances to dolphins. As a remote island chain, the Hawaiian Islands rely heavily on the marine environment for transportation, recreation, and fishing that aggregates into significant levels of vessel traffic. Given the known presence of dolphins in this region, there is a gap in knowledge regarding the relative exposure risk that vessel traffic poses to island-associated dolphin populations in Hawai‘i. This research identified the spatial distribution of pantropical spotted dolphins (Stenella attenuata) and common bottlenose dolphins (Tursiops truncatus) and determined the extent of their overlap with various categories of vessel traffic in Maui Nui, Hawai‘i. Species distribution was determined using kernel density estimates based on sighting data from 50 spotted dolphin sightings and 75 bottlenose dolphin sightings collected from 2013 to 2018. A combination of vessel GPS and Automatic Identification Systems (AIS) vessel tracks were used to quantify vessel traffic within the study area, resulting in 22,464 vessel tracks that were subsequently compiled into categories for analysis from 2014 to 2017. Risk of vessel exposure between vessels and dolphins, or co-occurrence, was determined by calculating the product of predicted dolphin density and predicted vessel density. Both species were exposed to vessel traffic risk over 100% of their distribution, but their highest exposure risk varied spatially, with high risk defined as > 0.25 on a normalized scale of low (0) to high (1) risk. The highest vessel exposure risk for spotted dolphins occurred in deeper, offshore waters, while the highest risk for bottlenose dolphins was in shallow, coastal waters. The vessel categories with the largest area of high risk to spotted dolphins were tour vessel and commercial fishing vessel traffic, while commercial transportation traffic had the highest exposure risk for bottlenose dolphins. This article provides baseline information for understanding the vulnerability of two island-associated dolphin populations to the threat of vessel traffic and highlights the differences in relative exposure risk based on species and vessel categories.
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Borges Costa, Ana Paula, Pedro Fruet, Fábio Gonçalves Daura-Jorge, Paulo César Simões-Lopes, Paulo Henrique Ott, Victor Hugo Valiati, and Larissa Rosa de Oliveira. "Bottlenose dolphin communities from the southern Brazilian coast: do they exchange genes or are they just neighbours?" Marine and Freshwater Research 66, no. 12 (2015): 1201. http://dx.doi.org/10.1071/mf14007.
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The genetic structure of bottlenose dolphin communities found along the southern Brazilian coast is reported in this study. Genetic structure analysis using biopsy samples from free ranging dolphins and tissue samples from stranded dolphins revealed a fine-scale population structure among three distinct groups. The first genetically distinct group was composed of resident dolphins of Laguna with a high degree of site fidelity. The second group was composed of one photo-identified dolphin, previously recognised by its interaction with fishermen, and dolphins that stranded near the mouth of Tramandaí Lagoon. Moderate nuclear and low mitochondrial gene diversity was found in dolphins of those coastal communities, whereas most of the dolphins stranded along the coast showed markedly higher levels of gene diversity at both markers. These stranded dolphins of unknown origin formed the third distinct group, which may be part of a larger offshore community. These results demonstrate the presence of at least three bottlenose dolphin clusters along this portion of the Brazilian coast, with the coastal specimens appearing to be only neighbours of a larger offshore community that eventually strands along the coast, highlighting the importance of the establishment of management and conservation measures for the species at a local scale.
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Hawkins, Elizabeth R., Mia Gustavsson, Lara Pogson-Manning, Heather Pheloung, and Christian Jaehnichen. "Prevalence of Skin Lesions and Injuries in Australian Humpback Dolphins (Sousa sahulensis) and Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) in Moreton Bay, Queensland." Aquatic Mammals 48, no. 4 (July 15, 2022): 297–313. http://dx.doi.org/10.1578/am.48.4.2022.297.
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Coastal dolphin populations are highly vulnerable due to their proximity to major urban centres and exposure to cumulative threats from anthropogenic activities. As bioindicators of environmental condition, it is crucial to understand and monitor the health of these coastal dolphin populations. Visual assessments of skin lesions on dolphins can provide useful insights into the health of these populations and exposure to environmental stressors. We examined the prevalence of skin lesions in Australian humpback dolphins (Sousa sahulensis) and Indo-Pacific bottlenose dolphins (Tursiops aduncus) of different age classes inhabiting the near-urban embayment of Moreton Bay, Queensland. The prevalence and extent of nontraumatic and traumatic skin lesions on individual dolphins were assessed using photographs taken during 103 boat-based surveys completed between 2014 and 2016. A total of 15 primary skin lesion categories were identified from 126 humpback and 100 bottlenose dolphins. Differences in the prevalence of skin lesions were evident between age classes and species. Nontraumatic skin lesions were prevalent in 48.4% of the humpback and 61.0% of the bottlenose dolphins. Comparatively, traumatic lesions were evident in almost all humpback (92.3%) and bottlenose (99.0%) dolphins. Anthropogenic-related injuries from entanglement in fishing gear and vessel strikes were substantial and significantly differed between species (p < 0.05). Injuries from fishing and vessel activities affected 11.0% of humpback dolphins and 30.0% of bottlenose dolphins, suggesting that these activities pose a major threat to these populations. Findings from this study provide an important baseline to inform ongoing health monitoring and conservation efforts of these vulnerable dolphin populations inhabiting a near-urban embayment.
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Le-Bert, Carolina R., Cynthia R. Smith, John Poindexter, Amanda Ardente, Jenny Meegan, Randall S. Wells, Stephanie Venn-Watson, Eric D. Jensen, and Khashayar Sakhaee. "Comparison of potential dietary and urinary risk factors for ammonium urate nephrolithiasis in two bottlenose dolphin (Tursiops truncatus) populations." American Journal of Physiology-Renal Physiology 315, no. 2 (August 1, 2018): F231—F237. http://dx.doi.org/10.1152/ajprenal.00606.2017.
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Dietary and urinary risk factors have been implicated in conditions favoring ammonium urate nephrolithiasis in managed dolphins compared with free-ranging dolphins. In this study, urine samples were collected from 16 dolphins (8 cases, 8 controls) from the U.S. Navy Marine Mammal Program for the purposes of assessing changes in urinary biomarkers after a large meal. Urinary biomarkers and nephrolithiasis presence were assessed opportunistically in 15 long-term resident free-ranging dolphins living in Sarasota Bay, Florida. Additionally, the total purine contents of fish commonly consumed by each dolphin population were measured to evaluate potential dietary risk factors. Populations were compared for total dietary purine composition, recently fed status, nephrolithiasis presence, and differences in urinary biochemical, acid-base, and physicochemical parameters via Wilcoxon rank sum analysis and least square means. Managed dolphins had higher urinary pH and ammonium ([Formula: see text]) in both pre- and postprandial conditions and higher urinary uric acid and saturation indices of NH4U in the postprandial condition compared with free-ranging dolphins ( P < 0.05). The purine content was greater ( P < 0.0001) in the diet consumed by managed dolphins [7 mmol/Mcal metabolizable energy (ME)] than in the free-ranging dolphin diet (4 mmol/Mcal ME). Free-ranging dolphins did not show evidence of nephrolithiasis. Observed differences in urinary biomarkers and dietary purine content in these two dolphin populations suggest a pathophysiologic basis for the role of fish types on the risk of NH4U stone formation. Future research should investigate fish type and feeding frequency, inhibitors and promoters, and alkalinizing therapy for reducing NH4U nephrolithiasis in dolphins.
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Fury, Christine A., and Peter L. Harrison. "Abundance, site fidelity and range patterns of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in two Australian subtropical estuaries." Marine and Freshwater Research 59, no. 11 (2008): 1015. http://dx.doi.org/10.1071/mf08109.
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Bottlenose dolphins are widely studied in marine habitats, but information on estuarine populations is very limited. The present study provides the first published data on bottlenose dolphins in Australian estuaries. Abundance estimates, site fidelity and individual ranging patterns were examined over a 3-year period for Indo-Pacific bottlenose dolphins (Tursiops aduncus) inhabiting the Clarence River (CR) and Richmond River (RR) estuaries in northern New South Wales, Australia. Mark–recapture analyses estimated 71 (62–81 95% CI) dolphins utilised the CR whereas 34 (19–49 95% CI) used the RR. Differences in site fidelity were observed between the estuaries, with 60% and 37% of identified dolphins determined as residents, 26% and 21% as occasional visitors and 14% and 42% as transients for the CR and RR respectively. Resource partitioning was apparent in both estuaries with the mean distance resident dolphins were found upstream from the river mouth being greater than occasional visitors and transients. The Clarence River sustains a larger, predominantly resident dolphin community compared with the Richmond River, which supports a relatively small dolphin community with lower site fidelity. Management of future increased anthropogenic disturbances is needed to ensure the long-term survival of these dolphin populations.
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Bouveroux, T., R. B. Tyson, and D. P. Nowacek. "Abundance and site fidelity of bottlenose dolphins in coastal waters near Panama City, Florida." J. Cetacean Res. Manage. 14, no. 1 (February 1, 2023): 37–42. http://dx.doi.org/10.47536/jcrm.v14i1.521.
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Dolphin watching and swim-with programmes are popular tourist attractions in Panama City, Florida, USA. Despite this, little is known about the population of dolphins that utilise this area, specifically St. Andrew Bay. To learn more about this population, photo-identification mark-recapture surveys were conducted between March 2004 and July 2007. The main objectives were to estimate the abundance of bottlenose dolphins inhabiting this region during this time period and to examine their patterns of site fidelity. Robust design population models were used to calculate seasonal abundance estimates, which ranged from 89 (CI 95% = 71–161) to 183 (CI 95% = 169–208) dolphins, even though 263 distinctive dolphins were identified during the study. Only 7% of dolphins (n = 18) observed were seen regularly in the study region. In addition, only 12% of dolphins (n = 30) observed had high site fidelity for the study region, while 58% (n = 153) were considered to be transient to the area. This study provides baseline information regarding dolphin abundance and site fidelity in and around St. Andrew Bay that may be used for the conservation and management of this dolphin population.
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McCormick, James G., and Sam H. Ridgway. "History of the Development of Anesthesia for the Dolphin." Anesthesiology 129, no. 1 (July 1, 2018): 11–21. http://dx.doi.org/10.1097/aln.0000000000002213.
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Abstract It is important for academic-minded human anesthesiologists to have an interdisciplinary perspective when engaging in cutting-edge research as well as the practice of human anesthesiology. This was a philosophy promoted by Dr. Robert Dripps, former pioneering Chairman of the Anesthesiology Department at the University of Pennsylvania (Philadelphia, Pennsylvania). Many human and veterinary anesthesiologists as well as biomedical engineers and neuroscientists benefited from Dr. Dripps’s constructive outlook personified in the quest to develop dolphin anesthesiology. The motivation to anesthetize dolphins came from the fact that scientists and physicians wanted to study the brain of the dolphin, a brain as large as man’s. Also, investigators wanted to develop anesthesia for the dolphin in order to study the electrophysiology of the dolphin’s highly sophisticated auditory system, which facilitates the dolphin’s amazing echolocation capability. Dolphin anesthesia involves a complex matter of unique neural control, airway anatomy, neuromuscular control of respiration, and sleep behavior.
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Baird, Ian G., and Isabel L. Beasley. "Irrawaddy dolphin Orcaella brevirostris in the Cambodian Mekong River: an initial survey." Oryx 39, no. 3 (July 2005): 301–10. http://dx.doi.org/10.1017/s003060530500089x.
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Irrawaddy dolphins Orcaella brevirostiris are found in coastal waters from the Bay of Bengal east to Palawan, Philippines and south to northern Australia. They also occur in three large tropical river systems in South-east Asia: the Mekong, Mahakam and Ayeyarwady. In March and May 1997 approximately 350 km of riverine habitat in parts of north-east Cambodia were surveyed, discussions took place with local people, and reported dry season dolphin habitat was mapped. Our objectives were to investigate the status, habitat and distribution of dolphins in north-east Cambodia and identify threats to the continued survival of dolphins in the Mekong River Basin. Nine groups of dolphins were observed in the Mekong River. A ‘best’ estimate of 40 animals were seen. Irrawaddy dolphins were generally confined to sections of the river with water levels >8–10 m during the dry season. It appears that the Mekong River dolphin population is rapidly declining. In 1997 there were probably no more than 100¨C150 dolphins left in north-east Cambodia (including southern Laos) and no more than 200 within the entire Mekong River Basin, although these numbers remain tentative. Anthropogenic mortality is high, albeit largely unintentional, and there is considerable risk that the dolphin population will become locally extinct in the Mekong River in the near future. The establishment of community-managed deep water Fish Conservation Zones with government support may represent the best opportunity for reducing dry season dolphin mortality from large-meshed gillnet entanglement. Efforts to establish protected areas for dolphins are currently underway.
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Aliaga- Rossel, Enzo, and Mariana Escobar-ww. "Translocation of trapped Bolivian river dolphins (Inia boliviensis)." IWC Journal of Cetacean Research and Management 21, no. 1 (September 10, 2020): 17–23. http://dx.doi.org/10.47536/jcrm.v21i1.96.
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The Bolivian river dolphin (Inia boliviensis), locally known as bufeo is an endemic species and categorized as Vulnerable in the Red Book of Vertebrates of Bolivia. Despite the fact that the Bolivian river dolphin is the only cetacean in land-locked Bolivia, knowledge about its conservation status and vulnerability to anthropogenic actions is extremely deficient. We report on the rescue and translocation of Bolivian river dolphins trapped in a shrinking segment of the Pailas River, Santa Cruz, Bolivia. Anthropogenic activities to alter the landscape and create agricultural land in the area include significant deforestation and irrigation channel construction and are likely to be a contributory factor causing the entrapment of these Bolivian River dolphins. The dolphins were trapped in shallow water in a 1 km section of river. Dry season water levels were rapidly falling and this section of river dried up completely. We collaborated with several institutions, authorities, and volunteers to translocate 26 Bolivian river dolphins, including calves, juveniles, and pregnant females. The dolphins were captured and transported using well-padded boats and vehicles and released into the Rio Grande. Each dolphin was accompanied by biologists who assured their welfare. No dolphins were injured or died during this process. If habitat degradation continue, it is likely that events in which river dolphins become trapped in South America may happen more frequently in the future.
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Leslie, Matthew S., and Phillip A. Morin. "Structure and phylogeography of two tropical predators, spinner ( Stenella longirostris ) and pantropical spotted ( S. attenuata ) dolphins, from SNP data." Royal Society Open Science 5, no. 4 (April 2018): 171615. http://dx.doi.org/10.1098/rsos.171615.
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Little is known about global patterns of genetic connectivity in pelagic dolphins, including how circumtropical pelagic dolphins spread globally following the rapid and recent radiation of the subfamily delphininae. In this study, we tested phylogeographic hypotheses for two circumtropical species, the spinner dolphin ( Stenella longirostris ) and the pantropical spotted dolphin ( Stenella attenuata ), using more than 3000 nuclear DNA single nucleotide polymorphisms (SNPs) in each species. Analyses for population structure indicated significant genetic differentiation between almost all subspecies and populations in both species. Bayesian phylogeographic analyses of spinner dolphins showed deep divergence between Indo-Pacific, Atlantic and eastern tropical Pacific Ocean (ETP) lineages. Despite high morphological variation, our results show very close relationships between endemic ETP spinner subspecies in relation to global diversity. The dwarf spinner dolphin is a monophyletic subspecies nested within a major clade of pantropical spinner dolphins from the Indian and western Pacific Ocean populations. Population-level division among the dwarf spinner dolphins was detected—with the northern Australia population being very different from that in Indonesia. In contrast to spinner dolphins, the major boundary for spotted dolphins is between offshore and coastal habitats in the ETP, supporting the current subspecies-level taxonomy. Comparing these species underscores the different scale at which population structure can arise, even in species that are similar in habitat (i.e. pelagic) and distribution.
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Pabst, D. A., A. S. Friedlaender, and W. A. McLellan. "Characterising an interaction between coastal bottlenose dolphins (Tursiops truncatus) and the spot gillnet fishery in southeastern North Carolina, USA." J. Cetacean Res. Manage. 3, no. 3 (May 24, 2023): 293–303. http://dx.doi.org/10.47536/jcrm.v3i3.880.
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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.
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Mateu, P., J. A. Raga, and F. J. Aznar. "Host specificity ofOschmarinella rochebruniandBrachycladium atlanticum(Digenea: Brachycladiidae) in five cetacean species from western Mediterranean waters." Journal of Helminthology 85, no. 1 (April 1, 2010): 12–19. http://dx.doi.org/10.1017/s0022149x10000180.
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AbstractWe investigated patterns of specificity of liver flukes (fam. Brachycladiidae) in a community of cetaceans from the western Mediterranean. The liver and pancreas of 103 striped dolphins,Stenella coeruleoalba, 18 Risso's dolphins,Grampus griseus, 14 bottlenose dolphins,Tursiops truncatus, 8 common dolphins,Delphinus delphis, and 5 long-finned pilot whales,Globicephala melas, were analysed for brachycladiid species. Two species were found:Oschmarinella rochebruniin striped dolphins (prevalence (P): 61.2%; mean intensity (MI) (95% CI): 34.2 (25.7–45.6)), andBrachycladium atlanticumin striped dolphins (P: 39.8%; MI: 7.1 (4.8–13.1)) and a single individual of common dolphin (P: 12.5%; intensity: 19), which represents a new host record. A molecular analysis using the internal transcribed spacer 2 (ITS2) region of the rDNA gene confirmed that specimens ofB. atlanticumwere conspecific regardless of host species. Available dietary data suggest that Risso's dolphins, bottlenose dolphins and long-finned pilot whales would contact rarely, if at all, the infective stages ofO. rochebruniandB. atlanticum. Neither the prevalence nor the mean abundance ofB. atlanticumdiffered significantly between striped and common dolphins, but a principal component analysis using seven morphometric variables indicated that specimens collected from the common dolphin were stunted. These worms also had fewer eggs compared with specimens typically found in striped dolphins, although the size of the eggs was similar in both host species. Dwarfism and low fecundity have typically been found in helminths infecting unusual host species, and might reflect the lower compatibility ofB. atlanticumfor common dolphins. In summary, bothO. rochebruniandB. atlanticumappear to exhibit a narrow specificity for striped dolphins in the western Mediterranean.
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Nollens, Hendrik H., Linda G. Green, Diane Duke, Michael T. Walsh, Beth Chittick, Scott Gearhart, Paul A. Klein, and Elliott R. Jacobson. "Development and Validation of Monoclonal and Polyclonal Antibodies for the Detection of Immunoglobulin G of Bottlenose Dolphins (Tursiops Truncatus)." Journal of Veterinary Diagnostic Investigation 19, no. 5 (September 2007): 465–70. http://dx.doi.org/10.1177/104063870701900502.
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Antibodies directed against species-specific immunoglobulin G (IgG) have a broad range of applications in serologic and immunologic research and in the development of clinical assays. Validated anti-IgG antibodies for marine mammal species are in short supply. The objective of this study was to produce and validate antibodies with specificity for IgG of the common bottlenose dolphin ( Tursiops truncatus). Bottlenose dolphin IgG was purified using protein G. Two mouse monoclonal antibodies and a rabbit polyclonal antibody were developed from mice and rabbits immunized with bottlenose dolphin IgG. The specificity of the monoclonal antibodies and the polyclonal antibody for bottlenose dolphin IgG was first verified by Western blot analysis and enzyme-linked immunosorbent assay (ELISA). For further validation, both monoclonal antibodies and the polyclonal antibody were incorporated in an indirect ELISA for the detection of the immune response of bottlenose dolphins to a vaccine antigen. Three bottlenose dolphins were immunized with a commercial Erysipelothrix rhusiopathiae vaccine, and serial blood samples were collected from all dolphins for measurement of levels of circulating antibodies. Seroconversion was observed in all 3 dolphins by use of both monoclonal antibodies and the polyclonal antibody. Circulating antibodies were detectable as early as 6 days after immunization in 1 dolphin. Peak antibody levels were detected 14 days after the immunization. The ability to detect seroconversion in all 3 immunized bottlenose dolphins firmly establishes the specificity of the monoclonal antibodies and the polyclonal antibody for IgG of the common bottlenose dolphin.
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Mason, Suzanne, Chandra Salgado Kent, David Donnelly, Jeffrey Weir, and Kerstin Bilgmann. "Atypical residency of short-beaked common dolphins ( Delphinus delphis ) to a shallow, urbanized embayment in south-eastern Australia." Royal Society Open Science 3, no. 9 (September 2016): 160478. http://dx.doi.org/10.1098/rsos.160478.
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Short-beaked common dolphins ( Delphinus delphis ) are typically considered highly mobile, offshore delphinids. This study assessed the residency of a small community of short-beaked common dolphins in the shallow, urbanized Port Phillip Bay, south-eastern Australia. The ability to identify common dolphins by their dorsal fin markings and coloration using photo-identification was also investigated. Systematic and non-systematic boat surveys were undertaken between 2007 and 2014. Results showed that 13 adult common dolphins and their offspring inhabit Port Phillip Bay, of which 10 adults exhibit residency to the bay. The majority of these adults are reproductively active females, suggesting that female philopatry may occur in the community. Systematic surveys conducted between 2012 and 2014 revealed that the dolphins were found in a median water depth of 16 m and median distance of 2.2 km from the coast. The shallow, urbanized habitat of this resident common dolphin community is atypical for this species. As a result, these common dolphins face threats usually associated with inshore bottlenose dolphin communities. We suggest that the Port Phillip Bay common dolphin community is considered and managed separate to those outside the embayment and offshore to ensure the community's long-term viability and residency in the bay.
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Coscarella, Mariano A., Silvana L. Dans, Enrique A. Crespo, and Susana N. Pedraza. "Potential impact of unregulated dolphin watching activities in Patagonia." J. Cetacean Res. Manage. 5, no. 1 (April 12, 2023): 77–84. http://dx.doi.org/10.47536/jcrm.v5i1.829.
Full textAbstract:
Since 1997, dolphin watching activities have increased in Patagonia, with dusky and Commerson’s dolphins as the target species. To assess the impact of this activity, dolphin watching tours were monitored. For dusky dolphins, the number of tourists increased from 1,393 in 1997 to 1,840 in 2000. The encounter rate grew from 25% during 1999 to 90% in 2001. Most of the groups observed ranged from 50-100 animals. Data were recorded from both a commercial and a research boat. Dusky dolphins showed a short-term reaction to boats and feeding was the most affected behaviour. For Commerson’s dolphins, the number of tourists increased from 532 in 1999 to 2,113 in 2001. The encounter rate averaged 95.58%. There is seasonality in the abundance of Commerson’s dolphins in the area during the colder months (May-December), when schools are larger, than in the warmer months. Dolphins showed a short-term reaction to the presence of the boat, performing aerial displays which are otherwise rarely seen. The direct gross estimated income for the companies carrying out dolphin watching is around US$60,000 per year. The activity has great potential to become an industry of its own. Nevertheless, the activity is at present undertaken on an irregular basis.
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Dans, Silvana Laura, Elvio Agustin Luzenti, Mariano Alberto Coscarella, Rocio Joo, Mariana Degrati, and Nadia Soledad Curcio. "Seasonal variation and group size affect movement patterns of two pelagic dolphin species (Lagenorhynchus obscurus and Delphinus delphis)." PLOS ONE 17, no. 11 (November 9, 2022): e0276623. http://dx.doi.org/10.1371/journal.pone.0276623.
Full textAbstract:
Movement is a key factor in the survival and reproduction of most organisms with important links to bioenergetics and population dynamics. Animals use movement strategies that minimize the costs of locating resources, maximizing energy gains. Effectiveness of these strategies depends on the spatial distribution, variability and predictability of resources. The study of fine-scale movement of small cetaceans in the pelagic domain is limited, in part because of the logistical difficulties associated with tagging and tracking them. Here we describe and model the fine-scale movement patterns of two pelagic dolphin species using georeferenced movement and behavioral data obtained by tracking dolphin groups on board small vessels. Movement patterns differed by species, group sizes and seasons. Dusky dolphin groups moved shorter distances when feeding and longer distances when traveling whereas the common dolphin did the same only when they moved in large groups. In summer, both dolphins cover longer distances in a more linear path, while in winter the movement is more erratic and moving shorter distances. Both species of dolphins prey on small pelagic fishes, which are patchily distributed and show seasonal variability in school sizes and distribution. However, dusky dolphins rely on anchovy to a larger extent than common dolphins. In Nuevo Gulf, anchovy shoals are smaller and separated by shorter distances in winter and dusky dolphins´ movement pattern is consistent with this. Dusky and common dolphins are impacted by tourism and fisheries. Further modelling of movement could be inform spatial based management tools.
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Dawson, Stephen M., and Elisabeth Slooten. "Management of gillnet bycatch of cetaceans in New Zealand." J. Cetacean Res. Manage. 7, no. 1 (March 15, 2023): 59–64. http://dx.doi.org/10.47536/jcrm.v7i1.758.
Full textAbstract:
Bycatch of dolphins in inshore gillnets first attracted scientific and management attention in New Zealand in the 1980s. During 1984-88, 50-150 dusky dolphins were killed each year at Kaikoura in gillnets set at the surface to catch bait for rock lobster. At the same time, annual catches of 20-100 Hector’s dolphins occurred in Canterbury waters in bottom-set commercial and recreational gillnets. These catches resulted in the banning of surface-set gillnetting at Kaikoura in 1989 and in the creation of the Banks Peninsula Marine Mammal Sanctuary in 1988 to protect Hector’s dolphin. An additional gillnet closure was established to protect North Island Hector’s dolphin in 2003. A key problem is that current information on catches in these and other areas is scant. One observer programme has been successfully implemented in a commercial gillnet fishery (Canterbury area, 1997/98 fishing season). Its estimate of Hector’s dolphin bycatch (17) is clearly unsustainable by the local population. Pingers have been voluntarily used in these fisheries, but there are no data establishing their effectiveness, and it has not been possible to ensure consistency of pinger use. There are no reliable estimates of numbers taken in recreational fisheries. Area closures are used to mitigate gillnet bycatch of Hector’s dolphin, however it appears that the Banks Peninsula Marine Mammal Sanctuary is not large enough to ensure the persistence of the Canterbury population. There is a bycatch limit in place for this population, although it is unenforced. We argue that management of this species via bycatch limits is not practical, however. Hector’s dolphin’s low abundance and separation into several distinct populations means that appropriate bycatch limits would be very small, and this necessitates very comprehensive observer coverage to be confident they are not exceeded. We propose that increasing the size of protected areas is the most reliable option for conservation.
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Rosmini, Rosmini, Zainuddin Zainuddin, and Syifa Nur Aini. "Legal Protection of Mahakam Dolphins Through Water Conservation Areas in Kutai Kartanegara Regency." Substantive Justice International Journal of Law 5, no. 1 (June 21, 2022): 1. http://dx.doi.org/10.56087/substantivejustice.v5i1.170.
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Mahakam dolphins are aquatic mammals (not fish) that live in freshwater rivers in the tropics and live in groups. The Mahakam dolphins, as endemic to the Mahakam River, is already threatened with extinction and needs protection to prevent the extinction from occurring. This paper explores the problems, namely the legal protection of the Mahakam Dolphin in Kutai Kertanegara Regency and the determination of conservation of the Mahakam Dolphin habitat area in Kutai Kertanegara Regency. The research method used is normative legal research (doctrinal) with the collection of legal materials. The results showed that the government of Kutai Kartanegara Regency has tried to protect the Mahakam dolphin through the establishment of the Mahakam Dolphins Habitat Water Conservation Area. This stipulation serves as an instrument in providing guidelines for the Regional Government and stakeholders in Kutai Kartanegara Regency in the context of organizing activities for the protection and preservation of the Mahakam dolphins.
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Daura-Jorge, F. G., M. Cantor, S. N. Ingram, D. Lusseau, and P. C. Simões-Lopes. "The structure of a bottlenose dolphin society is coupled to a unique foraging cooperation with artisanal fishermen." Biology Letters 8, no. 5 (May 2, 2012): 702–5. http://dx.doi.org/10.1098/rsbl.2012.0174.
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Diverse and localized foraging behaviours have been reported in isolated populations of many animal species around the world. In Laguna, southern Brazil, a subset of resident bottlenose dolphins ( Tursiops truncatus ) uses a foraging tactic involving cooperative interactions with local, beach-casting fishermen. We used individual photo-identification data to assess whether cooperative and non-cooperative dolphins were socially segregated. The social structure of the population was found to be a fission–fusion system with few non-random associations, typical for this species. However, association values were greater among cooperative dolphins than among non-cooperative dolphins or between dolphins from different foraging classes. Furthermore, the dolphin social network was divided into three modules, clustering individuals that shared or lacked the cooperative foraging tactic. Space-use patterns were not sufficient to explain this partitioning, indicating a behavioural factor. The segregation of dolphins using different foraging tactics could result from foraging behaviour driving social structure, while the closer association between dolphins engaged in the cooperation could facilitate the transmission and learning of this behavioural trait from conspecifics. This unique case of a dolphin–human interaction represents a valuable opportunity to explore hypotheses on the role of social learning in wild cetaceans.
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Lirazan, Machir Glib, Ericson Vince Ray Yulo, Maria Therese Kathleen Martir, Regie Antonette Salvilla, Jessica Oñate-Pacalioga, and Manuel Eduardo de la Paz. "Behavioral responses of Irrawaddy dolphins, Orcaella brevirostris (Owen in Grey, 1866) to fishing boats in a globally important marine mammal area in central Philippines." Palawan Scientist 14, no. 2 (December 26, 2022): 43–53. http://dx.doi.org/10.69721/tps.j.2022.14.2.06.
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The Irrawaddy dolphins, Orcaella brevirostris (Owen in Grey 1866) of Guimaras Strait, Philippines, have been known to utilize a core habitat within a coastal area surrounding the Bago River estuary in Negros Occidental. The dolphins’ close dependence on coastal waters often makes unavoidable direct interaction with human communities. Daily human activities in the coastal areas can pose serious threats to the dolphins, including high risk of entanglement in fishing nets, pollution, and disturbances caused by fishing boats and larger vessels. This study determined the behavior of dolphins toward different kinds of boats present in Bago-Pulupandan coastal waters. Factors identified to affect dolphin behavior towards boats include boat type (motorized or not), size, and distance from dolphins. Dolphin behavior towards boats were categorized as either positive, negative, or neutral. Results showed that the dolphins mostly exhibited neutral behavior towards boats, regardless of state and boat type. The dolphins’ passive behavior around vessels may make them more vulnerable to boat strikes, especially from speeding motorized boats. Recommendations include strict regulation of boat speed and traffic within their core habitat to minimize injuries, net entanglement, and avoid mortality.
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VAN WAEREBEEK, KOEN, MICHAEL GALLAGHER, ROBERT BALDWIN, VASSILI PAPASTAVROU, and Samira Mustafa Al-Lawati. "Morphology and distribution of the spinner dolphin, Stenella longirostris, rough-toothed dolphin, Steno bredanensis and melon-headed whale, Peponocephala electra, from waters off the Sultanate of Oman." J. Cetacean Res. Manage. 1, no. 2 (September 1, 1999): 167–77. http://dx.doi.org/10.47536/jcrm.v1i2.464.
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The morphology of three tropical delphinids from the Sultanate of Oman and their occurrence in the Arabian Sea are presented. Body lengths of four physically mature spinner dolphins (three males) ranged from 154- l78.3cm (median 164.5cm), i.e. smaller than any known stock of spinner dolphins, except the dwarf forms from Thailand and Australia. Skulls of Oman spinner dolphins (11 = I0) were practically indistinguishable from those of eastern spinner dolphins (Stenella longirosrris orientalis) from the eastern tropical Pacific, but were considerably smaller than skulls of populations of pantropical (Stene/la longirostris longirostris) and Central American spinner dolphins (Stenella !ongirostris centroamericana). Two colour morphs (CM) were observed. The most common (CMI) has the typical tripartite pattern of the pantropical spinner dolphin. A small morph (CM2), so far seen mostly off Muscat, is characterised by a dark dorsal overlay obscuring most of the tripartite pattern and by a pinkish or white ventral field and supragenital patch. Two skulls were linked to a CMI colour morph, the others were undetermined. It is concluded that Oman spinner dolphins should be treated as a discrete population, morphologically distinct from all known spinner dolphin subspecies. Confirmed coastal range states off the Arabian Peninsula include the United Arab Emirates, the Sultanate of Oman, Yemen, Somalia, Djibouti, Saudi Arabia, Sudan and Egypt. The taxonomic position of two damaged dolphin calvariae from Oman has been the issue of much debate. This paper discusses the cranial characteristics that allow positive identification as rough-toothed dolphin (Steno bredanensis) and melon-headed whale (Peponoceplwla electro) respectively. The calvariae represent the first confirmed specimen records of these dolphin species for the Arabian Sea sensu lato.
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Wei, Chong, Dorian Houser, Christine Erbe, Chuang Zhang, Eszter Matrai, James J. Finneran, and Whitlow W. Au. "Does rotation during echolocation increase the acoustic field of view? Comparative numerical models based on CT data of a live versus deceased dolphin." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A107. http://dx.doi.org/10.1121/10.0010799.
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Spinning is a natural and common dolphin behavior; however, its role in echolocation is unknown. We used computed tomography (CT) data of a live and a recently deceased bottlenose dolphin together with measurements of the acoustic properties of head tissues to perform acoustic property reconstrcution. The anatomical configuration and acoustic properties of the main forehead structures between the live and deceased dolphins were compared. Finite element analysis (FEA) was applied to simulate the generation and propagation of echolocation clicks, to compute their waveforms and spectra in both near- and far-fields, and to derive echolocation beam patterns. Model results from both the live and deceased dolphins were in good agreement with click recordings from live, echolocating individuals. FEA was also used to estimate the acoustic scene experienced by a dolphin rotating 180ãabout its longitudinal axis to detect fish in the far-field at elevation angles of 0ã–20ã. The results suggest that the spinning behavior provides a wider insonification area and compensates for the dolphin’s relatively narrow biosonar beam and constraints on the pointing direction that are limited by head movement. The results also have implications for examining the accuracy of FEA in acoustic simulations using freshly deceased specimens.
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Díaz-Santana, Pablo, Antonio Fernández, Josue Díaz-Delgado, Ana Isabel Vela, Lucas Domínguez, Cristian Suárez-Santana, Raquel Puig-Lozano, Carolina Fernández-Maldonado, Eva Sierra, and Manuel Arbelo. "Nocardiosis in Free-Ranging Cetaceans from the Central-Eastern Atlantic Ocean and Contiguous Mediterranean Sea." Animals 12, no. 4 (February 11, 2022): 434. http://dx.doi.org/10.3390/ani12040434.
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We report the pathologic features of nocardiosis in five free-ranging delphinids from the Canary Islands and Andalusia, namely four striped dolphins (Stenella coerulealba) and one bottlenose dolphin (Tursiops truncatus). All animals had a multiorgan (disseminated) pattern of infection involving suppurative to pyogranulomatous and thromboembolic lesions in two or more organs. Most affected organs were (by decreasing order) lung, pulmonary lymph nodes, liver, kidney, adrenal glands, and central nervous system. Typical intralesional and intravascular branched and filamentous bacteria were highlighted by Grocott’s methenamine silver and Gram stains. Bacterial analysis including 16S rRNA gene sequencing identified Nocardia farcinica in two striped dolphins and Nocardia otitidiscaviarum in one striped dolphin and the bottlenose dolphin. All dolphins tested (n = 4) for cetacean morbillivirus were negative; one dolphin had concurrent cutaneous herpesvirosis. These results provide the first record of N. otitidiscaviarum in cetaceans, the first account of N. farcinica in free-ranging dolphins, and confirmation of nocardiosis in central eastern Atlantic Ocean. These results expand the known geographic range of nocardiosis in cetaceans.
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Guinn, Makayla A., Christina N. Toms, Carrie Sinclair, and Dara N. Orbach. "Seasonal Prevalence of Skin Lesions on Dolphins across a Natural Salinity Gradient." Sustainability 16, no. 10 (May 18, 2024): 4260. http://dx.doi.org/10.3390/su16104260.
Full textAbstract:
Bottlenose dolphins (Tursiops truncatus) inhabit waters across a broad natural salinity gradient and exhibit changes in skin condition based on the quality of their environment. Prolonged exposure to low salinities (≤10–20 ppt) degenerates the epidermal barrier and causes cutaneous lesions in dolphins, while the role of high salinity exposure (>35 ppt) in lesion development remains unknown. We assessed seasonal lesion prevalence in three free-ranging dolphin stocks inhabiting coastal Gulf of Mexico (GoM) waters of different salinities (0–30 ppt, 22–35 ppt, and 36+ ppt) using images of dolphin bodies. Lesions were documented on 44% of the dolphins photographed (n = 432), and lesion occurrence was significantly related to cold seasons and water temperatures but not salinity. Cold water temperatures may heighten dolphin susceptibility to infectious pathogens and disease and compound the effects of anthropogenic pollutants in the GoM. As dolphins are a bioindicator species of marine habitat welfare, natural studies assessing dolphin skin may reveal environmental degradation with potential impacts on marine ecosystems and human health.
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Quintana Martín-Montalvo, Belén, Ludovic Hoarau, Ophélie Deffes, Sylvain Delaspre, Fabienne Delfour, and Anne-Emmanuelle Landes. "Dolphin Watching and Compliance to Guidelines Affect Spinner Dolphins’ (Stenella longirostris) Behaviour in Reunion Island." Animals 11, no. 9 (September 12, 2021): 2674. http://dx.doi.org/10.3390/ani11092674.
Full textAbstract:
Marine wildlife tourism has rapidly developed in Reunion Island, due to a large demand for interactions with a resident population of spinner dolphins (Stenella longirostris). The presence of dolphin-watching vessels close to dolphin groups can cause short-term impacts on their behaviour; cumulative incidences likely result in deleterious long-term impacts on the population. Using scan sampling, we collected behavioural data on spinner dolphins to evaluate the short-term effects of dolphin watching on their behaviour. The dolphins were less likely to begin socialising or diving while travelling and more likely to stay travelling and milling in the presence of vessels. Additionally, activity budgets for resting and socialising decreased simultaneously with increased travelling and milling. Avoidance responses significantly increased with an increase in the number of vessels and non-compliance with the local dolphin-watching guidelines. These behavioural responses are likely to have energetic costs for the dolphins, which may lead to decreased survival and reproductive success at individual and population levels. More restrictive regulations, increased surveillance and animal-based measures are key tools to adapt the conservation efforts in Reunion Island. Further studies on the island’s resident dolphin populations are necessary to ensure the continuity of dolphin-watching activities in a sustainable manner.
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Estep, J. S., R. E. Baumgartner, F. Townsend, D. A. Pabst, W. A. Mclellan, A. Friedlaender, D. G. Dunn, and T. P. Lipscomb. "Malignant Seminoma with Metastasis, Sertoli Cell Tumor, and Pheochromocytoma in a Spotted Dolphin (Stenella frontalis) and Malignant Seminoma with Metastasis in a Bottlenose Dolphin (Tursiops truncatus)." Veterinary Pathology 42, no. 3 (May 2005): 357–59. http://dx.doi.org/10.1354/vp.42-3-357.
Full textAbstract:
Seminoma with metastasis was diagnosed in a spotted dolphin ( Stenella frontalis) and an Atlantic bottlenose dolphin ( Tursiops truncatus). Sertoli cell tumor and pheochromocytoma were also diagnosed in the spotted dolphin. The spotted and bottlenose dolphins were adult males that stranded and died on the coasts of northwest Florida and southeast North carolina, respectively. Neoplasia is infrequently reported in cetaceans. This is the first report of seminoma, Sertoli cell tumor, and pheochromocytoma in a dolphin, the first report of three distinct neoplasms in a dolphin, and one of the few reports of malignant neoplasia in dolphins.
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Bavestrello, Giorgio, Riccardo Cattaneo-Vietti, Eleonora Meliadò, and Guido Gnone. "Dolphin bounty hunting in the history of the Italian fishery." IWC Journal of Cetacean Research and Management 21, no. 1 (September 10, 2020): 25–31. http://dx.doi.org/10.47536/jcrm.v21i1.184.
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In the Mediterranean, at the end of the 19thcentury, dolphins were identified as pest species for their disruptive actions during some fishing phases. Numerous fishermen organizations asked for permission to hunt dolphins, and the killing of a dolphin was often institutionally favoured by several national laws. We provide a picture of the systematic culling campaigns for dolphins in Italy up to the absolute prohibition of capture, analysing the governmental measures implemented against dolphins, the official number of individuals killed and their value (in Italian liras) in 11 Italian Maritime Compartments from 1927 to 1937. Officially, over 6,700 dolphins were killed in 10 years along the Italian coast and rewards distributed for about 360,160 Italian liras, which, at the current exchange rate, correspond to 355,000 euros, for a contribute of about 52 euros for each dolphin. Considering that the meat was consumed both at the family level or sold, mainly as salted and dried meat, the dolphin hunting could be considered a profitable activity in those years for the fishermen. Due to the scarce information available on the size of the dolphin populations around the Italian coast, it is difficult to estimate the impact of the bounty fishing on the Italian populations during the studied period. Nevertheless,it is possible to hypothesizethat it could have affected all the local recruitment, producing an effect on the local population far from being negligible.