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Dolphins
Kinds of Dolphins Terms modified by Dolphins Selected AbstractsSEXUAL DIMORPHISM AND BODY SCARRING IN THE BOTO (AMAZON RIVER DOLPHIN) INIA GEOFFRENSISMARINE MAMMAL SCIENCE, Issue 1 2006A. R. Martin Abstract Measurements and quantitative descriptions of a large sample of live adult botos (Inia geoffrensis) were obtained from the Mamirauá Reserve in the central Amazon. Males were on average 16% longer and weighed 55% more than females, demonstrating that this species is one of the most sexually dimorphic of all cetaceans for size. Males were also pinker than females, more heavily scarred by intraspecific tooth rakes, and had more life-threatening injuries. Some larger males had areas of modified skin that may simply be scar tissue, but may also be a heritable characteristic used as a shield or weapon. As in sperm whales, sexual size dimorphism and male-male aggression appear to be linked in botos, suggesting fierce competition for a resource,probably mating opportunities. The boto is unique among river dolphins in that males are larger than females. This distinction implies long evolutionary separation and fundamental differences in social behavior. [source] NON-LETHAL SHARK ATTACK ON A BOTTLENOSE DOLPHIN (TURSIOPS SP.) CALFMARINE MAMMAL SCIENCE, Issue 1 2006Quincy Anne Gibson First page of article [source] GEOGRAPHIC GENETIC STRUCTURE IN THE FRANCISCANA DOLPHIN (PONTOPORIA BLAINVILLEI)MARINE MAMMAL SCIENCE, Issue 2 2004Marila Lázaro Abstract The franciscana, Pontoporia blainvillei, is endemic to the South Atlantic coast of South America. The species is of conservation concern because it suffers elevated mortality rates due to incidental captures in fishing nets, and perhaps it is one of the most threatened small cetaceans in this region. Previous morphological and genetic studies have suggested the existence of at least two distinct stocks to the north and south of Santa Catarina Island in Brazil. Fixed differences were found between a sample from Rio de Janeiro and one from Rio Grande do Sul, in southern Brazil. Using 94 sequences of the control region of mitochondrial DNA, we examined the genetic structure of the species. We found no shared haplotypes between Rio de Janeiro and samples from the southern range of the species distribution. However, a phylogenetic analysis suggests that the former population is diphyletic with respect to the southern samples. This suggests that the populations have not been isolated long enough to reach reciprocal monophyly. Furthermore, genetic differentiation is broadly consistent with a simple model of isolation by distance, that therefore appears as an alternative to a model of strict isolation of two stocks. The estimated levels of gene flow are higher among neighboring populations, and decrease as more distant localities are compared. Finally, the molecular data suggest that franciscanas have expanded in Rio de Janeiro. [source] DUSKY DOLPHIN (LAGENORHYNCHUS OBSCURUS) FORAGING IN TWO DIFFERENT HABITATS: ACTIVE ACOUSTIC DETECTION OF DOLPHINS AND THEIR PREYMARINE MAMMAL SCIENCE, Issue 2 2004Kelly J. Benoit-Bird Abstract Active-acoustic surveys were used to determine the distribution of dusky dolphins and potential prey in two different New Zealand locations. During seven survey days off Kaikoura Canyon, dusky dolphins were found within the DeepScattering Layer (DSL) at 2000 when it rose to within 125 m of the surface. As the DSL rose to 30 m at 0100, the observed depth of dolphins decreased, presumably as the dolphins followed the vertical migration of their prey. Acoustically identified subgroups of coordinated animals ranged from one to five dolphins. Time, depth of layer, and layer variance contributed significantly to predicting foraging dusky dolphin subgroup size. In the much shallower and more enclosed Admiralty Bay, dolphins noted at the surface as foraging were always detected with the sonar, but were never observed in coordinated subgroups during the brief (two-day) study there. In Admiralty Bay dolphin abundance was correlated with mean volume scattering from potential prey in the water column; and when volume scattering, an index of prey density, was low, dolphins were rarely present. Ecological differences between the deep waters of Kaikoura Canyon and the shallow nearshore waters of Admiralty Bay may result in differences in how, when, and in what social groupings dusky dolphins forage. [source] SEXUAL ECOLOGY OF THE SPINNER DOLPHIN, STENELLA LONGIROSTRIS: GEOGRAPHIC VARIATION IN MATING SYSTEMMARINE MAMMAL SCIENCE, Issue 3 2003William F. Perrin Abstract We offer the first report for a cetacean of geographical variation in mating system based in morphology. Analysis of samples from 1,678 male spinner dolphins from the eastern Pacific revealed that testis + epididymis weight was greater (to 1,354 g) in the whitebelly form of the species than in the eastern form (to 843 g). Sexual dimorphism in dorsal-fin shape is greater in the eastern form. The difference in testis size was strongly linked with shape of the dorsal fin on an individual basis. Only a few eastern males (0.6%) reached testis + epididymis weight at which all epididymides contain sperm, while a much larger proportion of whitebelly spinners (15.2%) reached this level, suggesting that a smaller proportion of eastern spinner males may participate in reproductive activity. This, and the fact that increased dimorphism and decreased testis size are indicative of increased polygyny in a wide variety of other mammal species, leads to the conclusion that the mating system varies geographically in the species, with a gradient from a more polygynous mating system in the eastern form to a more open or polygynandrous mating system in the whitebelly form. Differences in ovulation rate in the two forms are consistent with this conclusion. [source] CRANIAL SEXUAL DIMORPHISM AND GEOGRAPHIC VARIATION IN ERASER'S DOLPHIN, LAGENODELPHIS HOSEIMARINE MAMMAL SCIENCE, Issue 3 2003William F. Perrin Abstract Knowledge of geographic variation is important to questions of population assessment and management. Fraser's dolphins have been exploited in two regions in the western Pacific. Analysis of 137 skulls from the Philippines, Japan, Taiwan, Australia, Indonesia, Malaysia, South Africa, France, the U.S., St. Vincent and the Grenadines, and the eastern tropical Pacific revealed sexual dimorphism in 5 of 26 measurements (difference of 1.9%-5.8% between males and females), similar to levels of cranial dimorphism in other small pelagic delphinids. Males had a larger braincase and temporal fossae and smaller external nares than females. Sexually dimorphic characters were excluded, and male and females samples were pooled to examine geographic differences in the remaining characters. Multivariate analyses yielded significant differences between the Philippine and Japanese series within the North Pacific and between a pooled North Pacific series and a North Atlantic series. The Japanese skulls were on average broader and had a wider rostrum, larger orbit, larger internal nares, and longer braincase than the Philippine skulls. These differences suggest that Fraser's dolphins exploited in Japanese and Philippine waters in directed fisheries or as by catch belong to different populations and should be assessed and managed separately. [source] INTERACTIONS BETWEEN THE INDIAN RIVER LAGOON BLUE CRAB FISHERY AND THE BOTTLENOSE DOLPHIN, TURSIOPS TRUNCATUSMARINE MAMMAL SCIENCE, Issue 4 2002Wendy D. Noke Abstract Anecdotal reports from blue crab fishermen in the Indian River Lagoon (IRL), Florida suggested that bottlenose dolphins (Tursiops truncatus) followed their boats, and stole bait fish from crab pots soon after they were deployed. To investigate these reports, we made biweekly observations from IRL commercial crab boats from January 1998 to January 1999 (670 h). Only 2.8% of the 18,891 crab pots surveyed revealed evidence of dolphin/crab pot interaction. Dolphin interactions included: (1) begging at boats, (2) feeding on discarded bait fish, (3) engaging in crab pot tipping behavior, and (4) dolphin mortality from crab pot float line entanglement. Overall, 16.6% of the 1,296 dolphins sighted interacted with fishing boats. Seasonal trends were evident, with fishery interactions peaking in the summer. Crab pot interactions ranged from 0% to 36% of the traps checked daily. Different methods of securing the bait-well door and the role of trap locality were tested using a replicated experimental design. Results showed significant differences in successful bait removal by dolphins, among the degrees of door security (P < 0.001) and between trap location (P < 0.01). Thus, increased door security may help to reduce the negative impacts to the fishery and dolphins involved. [source] HISTOLOGY OF THE OVARIES OF A BOTTLENOSE DOLPHIN, TURSIOPS ADUNCUS, OF KNOWN REPRODUCTIVE HISTORYMARINE MAMMAL SCIENCE, Issue 2 2002F. M. Brook [source] A PRELIMINARY EXAMINATION OF SEX DIFFERENCES IN TACTILE INTERACTIONS AMONG JUVENILE ATLANTIC SPOTTED DOLPHINS (STENELLA FRONTALIS)MARINE MAMMAL SCIENCE, Issue 4 2007J. Daisy Kaplan First page of article [source] THE SHORT-TERM BEHAVIORAL REACTIONS OF BOTTLENOSE DOLPHINS TO INTERACTIONS WITH BOATS IN DOUBTFUL SOUND, NEW ZEALANDMARINE MAMMAL SCIENCE, Issue 4 2006David Lusseau Abstract Doubtful Sound is home to one of the southernmost resident populations of bottlenose dolphins (Tursiops sp.). This population regularly interacts with scenic cruises. During these interactions, dolphins tend to horizontally and vertically avoid vessels, especially when the behavior of these vessels is intrusive. This study aimed at understanding the behavioral reactions of individuals to these interactions that lead to the disruption of the school's behavioral state. Observing the behavioral events performed by individuals during an interaction can help define the short-term reactions elicited by the boat presence. I recorded the behavioral events performed by all individuals of focal schools. The frequency of occurrence of all events was compared depending on the presence of vessels, their behavior, and the behavioral state of the focal school. Dolphins tended to perform more side flops while interacting with powerboats, a behavior which may be used as a non-vocal communication tool. Moreover, the movement of dolphins became more erratic during interactions with all types of vessels. These effects increased when the boats were more intrusive while interacting. This study shows that the impact of interaction with boats can be minimized if the vessels respect the guidelines in place. [source] FLIPPER RUBBING BEHAVIORS IN WILD BOTTLENOSE DOLPHINS (TURSIOPS ADUNCUS)MARINE MAMMAL SCIENCE, Issue 4 2006Mai Sakai Abstract "Flipper rubbing" behavior was quantitatively analyzed in wild Indo-Pacific bottlenose dolphins (Tursiops aduncus) around Mikura Island, Tokyo, Japan. We observed two types of flipper rubbing: (1) F-B rubbing; one dolphin (Rubber) rubbed its flipper over various parts of a partner's (Rubbee) body, and (2) F-F rubbing; both dolphins rubbed each other's anterior flipper edge in alternating shifts. F-B rubbings tended to be initiated by the Rubbee and were terminated by the Rubber. The Rubbee often moved actively its body part that was in contact with the Rubber's flipper, and assumed side-up, upside-down, or other postures while the Rubber remained horizontal in most cases. These facts suggest that the Rubbee engaged in F-B rubbing more actively than the Rubber, and might receive some benefit from the frictional contact during F-B rubbing. Dolphins often switched their roles as Rubber and Rubbee between episodes of flipper rubbing bout. Adults and sub-adults exchanged F-B rubbing and F-F rubbing most often with individuals of the same sex in the same age class. F-B rubbing was frequent in mother-and-calf dyads. Our results suggest that flipper rubbing is an affiliative behavior which could be a quantitative measure of social relationships among individuals of this species in future studies. [source] ABUNDANCE OF IRRAWADDY DOLPHINS (ORCAELLA BREVIROSTRIS) AND GANGES RIVER DOLPHINS (PLATANISTA GANGETICA GANGETICA) ESTIMATED USING CONCURRENT COUNTS MADE BY INDEPENDENT TEAMS IN WATERWAYS OF THE SUNDARBANS MANGROVE FOREST IN BANGLADESHMARINE MAMMAL SCIENCE, Issue 3 2006Brian D. Smith Abstract Independent observer teams made concurrent counts of Irrawaddy dolphins Orcaella brevirostris and Ganges River dolphins Platanista gangetica gangetica in mangrove channels of the Sundarbans Delta in Bangladesh. These counts were corrected for missed groups using mark-recapture models. For Irrawaddy dolphins, a stratified Lincoln-Petersen model, which incorporated group size and sighting conditions as covariates, and a Huggins conditional likelihood model, which averaged models that individually incorporated group size, sighting conditions, and channel width as covariates, generated abundance estimates of 397 individuals (CV = 10.2%) and 451 individuals (CV = 9.6%), respectively. For Ganges River dolphins, a stratified Lincoln-Petersen model, which incorporated group size as a covariate, and a Huggins conditional likelihood model, which averaged the same models described above, generated abundance estimates of 196 individuals (CV = 12.7%) and 225 individuals (CV = 12.6%), respectively. Although the estimates for both models were relatively close, the analytical advantages of the Huggins models probably outweigh those of the Lincoln-Petersen models. However, the latter should be considered appropriate when simplicity is a priority. This study found that waterways of the Sundarbans support significant numbers of Irrawaddy and Ganges River dolphins, especially compared to other areas where the species have been surveyed. [source] THE SOCIAL STRUCTURE OF BOTTLENOSE DOLPHINS, TURSIOPS TRUNCATUS, IN THE BAHAMASMARINE MAMMAL SCIENCE, Issue 4 2004Cindy A. Rogers Abstract The social structure of coastal ecotype bottlenose dolphins, Tursiops truncatus, is largely unknown as they inhabit regions far from shore. This study reports on a community of bottlenose dolphins , 27 km from Grand Bahama Island (May-September, 1993,2002). Resident and non-resident dolphins occurred in the area. Some dolphins traveled over 320 km between communities; others showed long- term site fidelity up to 17 yr. Average group size was 3,5, and was significantly larger with calves present and significantly smaller when traveling. The half-weight index was used to determine coefficients of association (COA) for individuals of known sex annually and for pooled years. Permutation tests revealed non-random associations and presence of preferred/avoided companions in all data sets. Annual COAs were low: female-female ,= 0.31, male-male ,= 0.30, and mixed-sex ,= 0.26. Mother-calf associations showed the highest values. Some males formed strong, long-term bonds. Female COAs fluctuated with reproductive status. Using pooled data, COAs were lower and the same basic trends were evident. However, strong associations seen in the annual data were not evident in pooled data. Bottlenose dolphins that inhabit offshore, shallow water show many of the same social structure characteristics as in well-studied coastal populations. [source] EFFECTS OF WATERCRAFT NOISE ON THE ACOUSTIC BEHAVIOR OF BOTTLENOSE DOLPHINS, TURSIOPS TRUNCATUS, IN SARASOTA BAY, FLORIDAMARINE MAMMAL SCIENCE, Issue 4 2004Kara C. Buckstaff Abstract Watercraft may provide the greatest source of anthropogenic noise for bottlenose dolphins living in coastal waters. A resident community of about 140 individuals near Sarasota, Florida, are exposed to a vessel passing within 100 m approximately every six minutes during daylight hours. I investigated the circumstances under which watercraft traffic may impact the acoustic behavior of this community, specifically looking for short-term changes in whistle frequency range, duration, and rate of production. To analyze whistles and received watercraft noise levels, acoustic recordings were made using two hydrophones towed from an observation vessel during focal animal follows of 14 individual dolphins. The duration and frequency range of signature whistles did not change significantly relative to vessel approaches. However, dolphins whistled significantly more often at the onset of approaches compared to during and after vessel approaches. Whistle rate was also significantly greater at the onset of a vessel approach than when no vessels were present. Increased whistle repetition as watercraft approach may simply reflect heightened arousal, an increased motivation for animals to come closer together, with whistles functioning to promote reunions. It may also be an effective way to compensate for signal masking, maintaining communication in a noisy environment. [source] DUSKY DOLPHIN (LAGENORHYNCHUS OBSCURUS) FORAGING IN TWO DIFFERENT HABITATS: ACTIVE ACOUSTIC DETECTION OF DOLPHINS AND THEIR PREYMARINE MAMMAL SCIENCE, Issue 2 2004Kelly J. Benoit-Bird Abstract Active-acoustic surveys were used to determine the distribution of dusky dolphins and potential prey in two different New Zealand locations. During seven survey days off Kaikoura Canyon, dusky dolphins were found within the DeepScattering Layer (DSL) at 2000 when it rose to within 125 m of the surface. As the DSL rose to 30 m at 0100, the observed depth of dolphins decreased, presumably as the dolphins followed the vertical migration of their prey. Acoustically identified subgroups of coordinated animals ranged from one to five dolphins. Time, depth of layer, and layer variance contributed significantly to predicting foraging dusky dolphin subgroup size. In the much shallower and more enclosed Admiralty Bay, dolphins noted at the surface as foraging were always detected with the sonar, but were never observed in coordinated subgroups during the brief (two-day) study there. In Admiralty Bay dolphin abundance was correlated with mean volume scattering from potential prey in the water column; and when volume scattering, an index of prey density, was low, dolphins were rarely present. Ecological differences between the deep waters of Kaikoura Canyon and the shallow nearshore waters of Admiralty Bay may result in differences in how, when, and in what social groupings dusky dolphins forage. [source] POPULATION STRUCTURE IN AN INSHORE CETACEAN REVEALED BY MICROSATELLITE AND mtDNA ANALYSIS: BOTTLENOSE DOLPHINS (TURSIOPS SP.) IN SHARK BAY, WESTERN AUSTRALIAMARINE MAMMAL SCIENCE, Issue 1 2004Michael Krützen Abstract We examined population substructure of bottlenose dolphins (Tursiops sp). in Shark Bay, Western Australia, using 10 highly polymorphic microsatellite loci, and mitochondrial DNA (mtDNA). For microsatellite analysis, 302 different animals were sampled from seven localities throughout the bay. Analysis of genetic differentiation between sampling localities showed a significant correlation between the number of migrants (Nm) calculated from FST, RST and private alleles, and distance between localities,a pattern of isolation-by-distance. For mtDNA, 220 individuals from all seven localities were sequenced for a 351 base pair fragment of the control region, resulting in eight haplotypes, with two distinct clusters of haplotypes. Values of FST and (,)ST for mtDNA yielded statistically significant differences, mostly between localities that were not adjacent to each other, suggesting female gene flow over a scale larger than the sampled localities. We also observed a significant correlation between the number of female migrants calculated from FST and ,ST and the distance of sampling localities. Our results indicate that dispersal in female dolphins in Shark Bay is more restricted than that of males. [source] A MODEL LIFE TABLE FOR BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) FROM THE INDIAN RIVER LAGOON SYSTEM, FLORIDA, U.S.A.MARINE MAMMAL SCIENCE, Issue 4 2003Megan K. Stolen Abstract Data gathered from 220 stranded bottlenose dolphins (Tursiops truncatus) in the Indian River Lagoon system, Florida, were used to derive a life table. Survivorship curves were fit to the data using Siler's competing-risk model and a maximum likelihood approach. Population growth was estimated to be between r= 0.0 and 0.046 based on the observed numbers of stranded dolphins. Variance in survival rates was estimated using an individual-based, age-structured population projection model. We estimate that the overall annual mortality rate for this population was 9.8% per year. Sex-specific differences in survivorship were apparent with females outliving males. The overall mortality curve resembles that of other large mammals, with high calf mortality and an exponentially increasing risk of senescent mortality. The inclusion of live-capture removals of individuals from this population did not significantly affect the estimation of survival parameters for most age classes. [source] FEEDING PREFERENCES OF THE MONKEY MIA DOLPHINS: RESULTS FROM A SIMULTANEOUS CHOICE PROTOCOLMARINE MAMMAL SCIENCE, Issue 4 2003Lawrence M. Dill Abstract The semiwild beach-feeding bottlenose dolphins (Tursiops aduncus) of Monkey Mia, Western Australia, provide an unparalleled opportunity to examine prey preference of this species. In a series of binary-choice feeding experiments, we took advantage of the animals' willingness to be fed by hand, to explore their preferences for fish species, size, and state (freshly caught or previously frozen). At the end of each beach visit, each dolphin was provided with a pair of fish but allowed to eat only the first one chosen. The dolphins appeared indifferent among the three species of fish offered to them (yellowtail trumpeter, Amniataba caudovittatus; striped trumpeter, Pelates sexlineatus; and western butterfish, Pentapodus vitta), which were of similar body form and matched for mass. Overall, the dolphins showed a slight preference for the larger of two yellowtail trumpeter offered, suggesting the capability for rational choice when there was a basis for it (most likely energy in this case), although there was considerable individual variation. The dolphins did not distinguish between freshly caught and previously frozen yellowtail. The methodology we describe can be used to generate data of potential value for understanding food and habitat selection of wild dolphins, and for modifying management practices for semiwild dolphins at Monkey Mia and elsewhere. [source] Notes: FOOD AND PARASITES FROM TWO HOURGLASS DOLPHINS, LAGENORHYNCHUS CRUCIGER (QUOY AND GAIMARD, 1824), FROM PATAGONIAN WATERSMARINE MAMMAL SCIENCE, Issue 4 2003Mercedes Fernández [source] ABUNDANCE OF BOTTLENOSE DOLPHINS IN THE BAYS, SOUNDS, AND ESTUARIES OF NORTH CAROLINAMARINE MAMMAL SCIENCE, Issue 1 2003Andrew J. Read We conducted a mark-recapture survey of bottlenose dolphins Tursiops truncatus in the bays, sounds, and estuaries of North Carolina during July 2000, using photographic identification techniques. During this survey we took 7,682 photographs of dolphins and, of these, 3,457 images were of sufficient quality for analysis. We identified 306 dolphins from distinctive nicks and notches on their dorsal fins. Eighry-six dolphins were photographed on more than one occasion during the course of the survey; one dolphin was photographed on four separate days. We then applied the results of our photographic analyses to several mark-recapture models and examined potential violations of the assumptions of these models, including an unexpected correlation between photo quality and mark distinctiveness. Our analysis suggests that our results are robusr to possible violations of these assumptions. The resulting estimates were then scaled to account for the proportion (0.46) of unmarked dolphins in the population. Our best estimate of the number of dolphins present in the inshore waters of North Carolina during July 2000 is 1,033 with a 95% Confidence Interval of 860,1,266 (CV = 0.099). Most dolphins were found in the northern part of the study area, which includes the second largest estuarine system in the United States. [source] GROWTH OF BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) FROM THE INDIAN RIVER LAGOON SYSTEM, FLORIDA, U. S. A.MARINE MAMMAL SCIENCE, Issue 2 2002Megan K. Stolen Abstract Gompertz growth models were fitted to total lengths and ages from tooth sections of 199 stranded bottlenose dolphins (Tursiops truncatus) from the Indian River Lagoon system, eastern Florida. Based on the model, dolphins from this population are estimated to be born at 119 cm and reach asymptotic length at 250 cm. No apparent pubescent growth acceleration was noted for either sex. Males appeared to grow to slightly longer lengths than females. There were small size differences between Indian River dolphins and those in Texas and Sarasota, indicating general size similarities between North Atlantic and Gulf of Mexico bottlenose dolphins stocks. [source] MOLECULAR SYSTEMATICS OF RIVER DOLPHINS INFERRED FROM COMPLETE MITOCHONDRIAL CYTOCHROME- B GENE SEQUENCESMARINE MAMMAL SCIENCE, Issue 1 2002Guang Yang Abstract 1,140 bp of the complete mitochondrial cytochrome- b gene sequences of baiji (Lipotes vexillifer), franciscana (Pontoporia blainvillei), and Ganges river dolphin (Platanista gangetica gangetica) were determined to address the systematic position and phylogeny of extant river dolphins with combination of homologous sequences of other cetaceans. The neighbor-joining (NJ), maximum parsimony (MP), and maximum likelihood (ML) phylogenetic analyses all identified the river dolphins into three lineages, i. e., Platanista, Lipotes, and Inia+Pontoporia. The Lipotes did not have sister relationship with either Platanista or Inia+Pontoporia, which strongly supported the referral of Lipotes to a separate family, i. e., Lipotidae. There were very high sequence divergences between all river dolphin genera, suggesting a relatively longer period of separation time than those among other odontocete families. [source] A RESIDENT POPULATION OF INDO-PACIFIC BOTTLENOSE DOLPHINS (TURSIOPS ADUNCUS) IN AMAKUSA, WESTERN KYUSHU, JAPANMARINE MAMMAL SCIENCE, Issue 1 2002Miki Shirakihara Abstract Residency patterns and population size were examined for Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the coastal waters of Amakusa-Shimoshima Island, western Kyushu, Japan, from summer 1994 to fall 1998. A total of 203 individuals were identified. The number of newly identified individuals barely increased after the first 1.5 yr. The identified individuals in one season were frequently resighted with percentages of mostly over 60% during the subsequent seasons. Most of the dolphins off Amakusa were yearround residents, although the total range of their habitat was unknown. The population size estimated by the mark-recapture technique was 218 individuals with a CV of 5.41% in 1995,1997. The group commonly consisted of more than 100 individuals. The large group size was thought to be a response to feeding on schooling fishes. [source] INCREASED AVOIDANCE OF SWIMMERS BY WILD BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) DUE TO LONG-TERM EXPOSURE TO SWIM-WITH-DOLPHIN TOURISMMARINE MAMMAL SCIENCE, Issue 4 2001Rochelle Constantine Abstract The responses of wild, non-provisioned bottlenose dolphins (Tursiops truncatus) to swim attempts from commercial swim-with-dolphin tour boats were systematically observed during two research periods: 1994,1995 and 1997,1998. A total of 255 groups of dolphins was encountered during boat-based surveys and 36% (n= 93) were exposed to at least one swim attempt. The operators' success with swim attempts, defined as at least one dolphin milling within 5 m of at least one swimmer, decreased from 48% in 1994,1995 to 34% in 1997,1998, and avoidance responses to swimmers increased from 22% to 31%. Dolphin response was found to vary according to swimmer placement. The greatest increase in avoidance occurred when swimmers were placed in the dolphins' path of travel. Based on sighting records of 266 individually identified dolphins, it was estimated that an average dolphin was exposed to 31 swim attempts per year. This level of exposure suggests that individual dolphins have, with cumulative experience, become sensitized to swim attempts. When a swim attempt was successful, on average it involved 19% of the group. Age-class differences in interaction rates showed that juveniles were significantly more likely to interact with swimmers than adults. This study highlights the importance of longitudinal studies in evaluating human impact and suggests the urgent need for similar studies of potential human impact on other toothed cetaceans. [source] COASTAL BOTTLENOSE DOLPHINS FROM SOUTHEASTERN AUSTRALIA ARE TURSIOPS ADUNCUS ACCORDING TO SEQUENCES OF THE MITOCHONDRIAL DNA CONTROL REGIONMARINE MAMMAL SCIENCE, Issue 2 2001Luciana M. Möller Abstract Sequence analysis of the mitochondrial DNA control region was used to clarify the taxonomic status of two coastal bottlenose dolphin populations from southeastern Australia currently classified as Tursiops truncatus. A 368-bp segment of the control region of 57 biopsy-sampled, photo-identified dolphins of Jervis Bay and Port Stephens was compared to published sequences of T. truncatus and T. aduncus from different oceanic regions. Sequence divergence between haplotypes from southeastern Australia and T. aduncus was much lower than that from T. truncatus. Analyses using two different methods of phylogenetic reconstruction unambiguously placed all haplotypes from southeastern Australia in a group composed exclusively of T. aduncus. The results strongly indicated that these two bottlenose dolphin populations belong to T. aduncus, extending the range of the species to subtropical waters of the Western South Pacific Ocean. [source] Conservation Focus: Baiji, Freshwater DolphinCONSERVATION BIOLOGY, Issue 3 2006Devra G. Kleiman No abstract is available for this article. [source] Neuroanatomy of the Subadult and Fetal Brain of the Atlantic White-sided Dolphin (Lagenorhynchus acutus) from in Situ Magnetic Resonance ImagesTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 12 2007Eric W. Montie Abstract This article provides the first anatomically labeled, magnetic resonance imaging (MRI) -based atlas of the subadult and fetal Atlantic white-sided dolphin (Lagenorhynchus acutus) brain. It differs from previous MRI-based atlases of cetaceans in that it was created from images of fresh, postmortem brains in situ rather than extracted, formalin-fixed brains. The in situ images displayed the classic hallmarks of odontocete brains: fore-shortened orbital lobes and pronounced temporal width. Olfactory structures were absent and auditory regions (e.g., temporal lobes and inferior colliculi) were enlarged. In the subadult and fetal postmortem MRI scans, the hippocampus was identifiable, despite the relatively small size of this structure in cetaceans. The white matter tracts of the fetal hindbrain and cerebellum were pronounced, but in the telencephalon, the white matter tracts were much less distinct, consistent with less myelin. The white matter tracts of the auditory pathways in the fetal brains were myelinated, as shown by the T2 hypointensity signals for the inferior colliculus, cochlear nuclei, and trapezoid bodies. This finding is consistent with hearing and auditory processing regions maturing in utero in L. acutus, as has been observed for most mammals. In situ MRI scanning of fresh, postmortem specimens can be used not only to study the evolution and developmental patterns of cetacean brains but also to investigate the impacts of natural toxins (such as domoic acid), anthropogenic chemicals (such as polychlorinated biphenyls, polybrominated diphenyl ethers, and their hydroxylated metabolites), biological agents (parasites), and noise on the central nervous system of marine mammal species. Anat Rec, 2007. © 2007 Wiley-Liss, Inc. [source] A Morphological and 13C NMR Study of the Extramandibular Fat Bodies of the Striped Dolphin (Stenella coeruleoalba)THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 7 2007C. Maxia Abstract The molecular and histological structure of the fat bodies covering externally the posterolateral region of the jaw of the striped dolphin (Stenella coeruleoalba) was investigated by means of morphological and nuclear magnetic resonance techniques. The analyses of samples belonging to adult and juvenile individuals were performed with the aim of seeking the presence of age-related differences. In our study, the level of isovalerate (iso5:0) in the extramandibular fat of the juvenile individuals is comparable with those of the adult counterparts; conversely, longer isobranched fatty acids were detected in lower quantities in the juveniles together with a higher degree of unsaturation. The morphologic analyses revealed that, in both adults and juveniles, this fatty tissue is similar to univacuolar adipose tissue. However, in the juveniles, a muscular component was present, whereas only in adult subjects, enlarged and irregularly shaped cavities may be seen within the adipose tissue. These cavities, structurally organized as veins, may regulate blood flow in response to changing water temperature and stabilize thermal gradient within the jaw lipids. These data suggest that the molecular components and the histological organization can indicate a maturation of the organ with age that probably may reflect different sound reception properties. Anat Rec, 2007. © 2007 Wiley-Liss, Inc. [source] Histological Structure of the Adrenal Gland of the Bottlenose Dolphin (Tursiops truncatus) and the Striped Dolphin (Stenella coeruleoalba) from the Adriatic SeaANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 1 2010S. Vukovi Summary The structure of the adrenal gland was studied in 11 bottlenose dolphins (Tursiops truncatus), and five striped dolphins (Stenella coeruleoalba). These species are legally protected in Croatia. All examined animals died of natural causes and were found stranded along eastern Adriatic coast. In both species the adrenal gland consists of a cortex and a medulla; the cortex is divided into three zones. Whereas in the bottlenose dolphin, there is a zona arcuata which contains columnar cells arranged in the form of arches; in the striped dolphin this zone is replaced by zona glomerulosa containing rounded clusters of polygonal cells. In both species, the zona fasciculata consists of radially oriented cords of polygonal cells, whereas in zona reticularis cells are arranged in branching and anastomosing cords. The adrenal medulla in both species contains dark, epinephrine-secreting cells and light norepinephrine-secreting cells. Epinephrine-secreting cells are localized in the outer part of the medulla, whereas norepinephrine-secreting cells are found in the inner part, arranged in clusters and surrounded by septa of thin connective tissue. The gland is surrounded by a thick connective-tissue capsule, from where thick trabeculae extend towards the interior. In the bottlenose dolphin, group of cells resembling both medullar and cortical cells can be seen within the capsule; whereas only groups of cells resembling cortical cells are found within the capsule of the striped dolphin. In the bottlenose dolphin invagination of the adrenal cortex into the medulla is obvious as well as medullary protrusions extending through cortex to the connective tissue capsule. [source] Scanning Electron Microscopy of the Orbital Harderian Gland in the Male Atlantic Bottlenose Dolphin (Tursiops truncatus)ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 4 2009G. G. Ortiz Summary The ultrastructure of the Harderian gland of Atlantic bottlenose dolphin (Tursiops truncatus) was examined by scanning electron microscopy (SEM). We found the following surface features: the typical round appearance of the ascinar glandular unit with a finely granular surface, a thin cortex and immediately below two types of cells: type I cells (characterized by small lipid vacuoles) and type II cells (characterized by large lipid vacuoles). It has been suggested that different cells forms represent a single cell type in varying activity states. Additionally, a coalescent tubular complex, a small balloon-like structures and large globular structures were observed. These structures may be reservoirs of secretion products. [source] | |||||||||||||||||||||||||||||||