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The First Confirmed Successful Refloat of a Stranded Bottlenose Dolphin (Tursiops truncatus) in Ireland and Subsequent Resighting with a Neonate
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... We determined age class through individual size and body length (Smith, Pollock, Waples, Bradley, & Bejder, 2013), reproductive state, and/or knowledge of long-term life history (Baker et al., 2018a). Adults were fully grown animals (about 4 m in length) and well-known from long-term photoidentification studies in the Shannon Estuary (e.g., Berrow, Holmes, & Kiely, 1996;Berrow et al., 2012;Ingram, 2000;O'Brien et al., 2014). Juveniles were less than two-thirds the size of adults and were not dependent on their mothers. ...
omplex mammalian societies. In this study, we analyzed the fine‐scale sociality of wild bottlenose dolphins in the Shannon Estuary, Ireland, by examining associations between members of the whole population and between specific female and male dolphins. We carried out 51 boat‐based individual focal follows on 18 identifiable bottlenose dolphins over 90.8 hr (39 days) between 2014 and 2016. Additionally, we conducted 353 boat‐based surveys (with 607 sightings) between 2012 and 2015, and identified 121 distinct adult/juvenile dolphins. The mean group size of focal dolphin groups was 7.2 ± 4.1 (range = 1–20) and the mean fission‐fusion rate was 3.06 ± 1.35 changes/hr. The most frequent composition of within‐group affiliate pairs was female–male. Focal males spent more time with female nearest‐neighbors than male nearest‐neighbors (p = .013). Differences between female and male activity budgets were not strongly supported (p = .13). There was no evidence for male alliance formation in the Shannon Estuary population, and all of the known‐sex top‐ranked associates (7) of known males (n = 10) were females. This research reveals a distinct bottlenose dolphin society with female–male affiliations and an absence of male alliances.
... Long-term photo-identification studies of bottlenose dolphins in the Shannon Estuary have been ongoing since the early 1990s (Berrow et al. 1996(Berrow et al. , 2012Ingram 2000;O'Brien et al. 2014). Additionally, over this time period, a dolphin-watching tourism industry has been established in which two main companies operate dolphin-watching tour boats and provide opportunistic platforms for research (Berrow and Holmes 1999). ...
Social and network analyses that incorporate information on individuals within a population enhance our knowledge of complex species. In this study, the social structure of wild bottlenose dolphins in the Shannon Estuary, Ireland, was analyzed by examining the dynamics of the whole population and then of individuals classed by sex, age, and area. One hundred and twenty-one dolphins were identified during 522 sightings between 2012 and 2015. The mean half-weight association index (HWI) of the population was 0.07 ± 0.02. The highest HWIs for individuals of known sex were for female-male pairs. Mean within-class HWI was significantly higher than mean between-class HWI for both age and area classes. Ordinations and sociograms were used to visualize social networks. Permutation tests revealed nonrandom associations for the population overall and both between and within classes. Temporal analyses showed associations persisting for >1,000 d. The whole population's best fit model was for two levels of casual acquaintances. Movement analyses demonstrated the use of the inner estuary by only 25% of the population revealing a potential community division by area. The difference between mean HWI when socializing (0.09 ± 0.03) compared to foraging (0.06 ± 0.03) was significant. These results highlight the importance of localized research, reflecting the complexity found in bottlenose dolphin societies globally.
A description of the social structure of a species is a first step toward understanding its social organization and, ultimately, the evolutionary processes that shaped its social system. Since the mid-1960s the rapid accumulation of information from field studies of terrestrial mammals has made it possible to propose models to explain the evolution of mammalian social systems. These models have examined the species distribution of characteristics such as group size, group compositions, spatial patterns of individuals, and social interactions in relation to environmental variables (for example, Crook and Gartlan, 1966; Eisenberg et al., 1972; Clutton-Brock, 1974; Jarman, 1974; Emlen and Oring, 1977; Wrangham, 1980). Predictable patterns of organization have been found which provide insights into the adaptive significance of the social systems. Until recently, available information for cetaceans has been inadequate to allow construction of comparable models. A surge of systematic field studies of the behavior and ecology of cetaceans is beginning to provide the requisite information for examination of cetacean societies within a general mammalian context. To this end, this chapter presents the results of one study of the social structure of the bottlenose dolphin, Tursiops truncatus.
Group size, site fidelity and abundance of bottlenose dolphins, Tursiops truncatus, were assessed during 392 photo-identification surveys conducted during 1997-1999 in the Drowned Cayes region, near Belize City, Belize, Central America. During this study 2155 dolphins were sighted across 736 groups. Mean group size was 2.9 (SD = 2.32) which is one of the smallest reported for bottlenose dolphins. One hundred and fifteen individual dolphin were photographically identified, with sighting frequencies ranging from one to fifty
(X¯ = 8.1, SD = 9.05). Thirty percent of identified dolphins were judged to be residents, while 23% were
photographed only once. Chao’s Mth model for closed populations was used to derive an abundance
estimate of 122 dolphins (95% CI = 114 -140). This low abundance estimate and a leveling trend in the
rate of newly identified individuals, indicates that the Drowned Cayes dolphin population is both
small and finite. Group size, abundance, and site fidelity comparisons were made with a 4-yr photoidentification study conducted at nearby Turneffe Atoll. Both the Drowned Cayes and Turneffe Atoll
studies had similarly small group sizes, low and variable levels of site fidelity and low abundance
estimates, but there was no overlap between individual sightings in the two areas. The observed behavioral
patterns and similarities between the two studies raise concerns that increasing pressures on Belize’s marine resources may pose a threat to its bottlenose dolphins.
The feasibility of developing commercial whale-watching in the Shannon Estuary was investigated by determining the distribution and abundance of bottle-nosed dolphins in the estuary. A variety of field techniques were employed, including photo-identification, fixed boat transects, scan sampling, minimum number estimates and the collection of incidental sightings over an eighteen-month period. Land-based observations showed that the presence of dolphins was influenced by the state of the tide, with a peak in sightings recorded three hours after high water. Dolphins were observed on 25 (61%) of 41 boat transects surveyed, of which sixteen turned into encounters, with dolphins sometimes present for many hours. A minimum number estimate conducted on 16 October 1994 showed that at least 56-68 animals were present, and photo-identification has recognised 25 animals individually. Dolphins were often recorded in discrete areas, especially off Kilcredaun Head, Beal Bar and off Leek Point. Sighting records from the Tarbert to Killimer ferry showed that dolphins were regularly seen especially in the spring and summer (May to August), being recorded on up to 88% of days in the month. Photo-identification showed that the same dolphins were present in the estuary throughout the study period, suggesting that they were resident. This is the first known resident population of bottle-nosed dolphins in Ireland. The implications of this work for the development of commercial dolphin-watching in the estuary are discussed.
An abundance assessment of bottlenose dolphins (Tursiops truncatus) in the Lower River Shannon candidate Special Area of Conservation (cSAC) was undertaken between July and October 2010 using photo-identification. European Union Member States are obliged to designate SACs for bottlenose dolphins to protect important habitats. The Lower River Shannon is the only cSAC in Ireland for this species. A cumulative total of 273 bottlenose dolphins were photographed during the 12 transects, and from these a total of 116 individual animals were identified. They were categorized as follows: 71 with Severity Grade 1 marks, 21 with Severity Grade 2 marks, and 24 with Severity Grade 3 marks. There were 50 dol-phins with permanent marks (Severity Grade 1) recorded on both sides of the dorsal fin, 64 on the left hand side only, and 57 on the right hand side only. There was an overlap, with some dolphins occurring in more than one category. Estimates of abundance were calculated using left side, right side, and both side identifications. The proportion of dolphins with re-identifiable marks (Severity Grade 1 only) ranged from 0.60 to 0.63. The estimated abundance of marked individuals was elevated depending on the estimated proportion of marked individuals in the population to give a final estimate of 107 ± 12, CV = 0.12 (95% CI = 83 to 131). Previous abundance estimates for bottlenose dolphins in the Lower River Shannon cSAC ranged from 114 in 2008 to 140 in 2006; the present estimate was within this range and also within the 95% Confidence Intervals for all sur-veys carried out to date. This suggests that, within the power of the survey technique, the population of bottlenose dolphins in the Lower River Shannon cSAC is relatively stable.
The bottlenose dolphins in Cork Harbour were studied using photo-identification to monitor individual dolphins and to assess whether they were resident in the area or transients. Landbased observations were carried out, to examine how the occurrence of dolphins varied over time and were influenced by the tidal cycle.
Images of 120 individual bottlenose dolphins from around the Irish coast were obtained from three photo-identification catalogues. Twenty three individuals were subsequently re-sighted, which is a re-sighting rate of 19%. The distance between re-sightings ranged from 130 to 650km and the duration from 26 to 760 days. Images were also compared to a catalogue of resident dolphins from the Shannon Estuary candidate Special Area of Conservation and from Wales but no matches were found. This short study provides strong evidence that bottlenose dolphins in Irish coastal waters are regularly undertaking large movements around the entire Irish coast and must be considered highly mobile and transient. These results have important implications for the conservation and management of this species.
"This excellent introduction on the biology of the bottlenose dolphin also provides a review of conservation issues and outlines current knowledge of dolphins in general. . . . for students, professionals, and anyone interested in the bottlenose dolphin."--Charles W. Potter, National Museum of Natural History"The Bottlenose Dolphin"presents for the first time a comprehensive, colorfully illustrated, and concise overview of a species that has fascinated humans for at least 3,000 years.After reviewing historical myths and legends of the dolphin back to the ancient Greeks and discussing current human attitudes and interactions, the author replaces myths with facts--up-to-date scientific assessment of dolphin evolution, behavior, ecology, morphology, reproduction, and genetics--while also tackling the difficult issues of dolphin conservation and management.Although comprehensive enough to be of great value to professionals, educators, and students, the book is written in a manner that all dolphin lovers will enjoy. Randall Wells s anecdotes interspersed throughout the work offer a first-hand view of dolphin encounters and research based on three decades working with them. Color photographs and nearly 100 black and white illustrations, including many by "National Geographic"photographer Flip Nicklin, beautifully enhance the text. Readers of "The Bottlenose Dolphin"will better appreciate what dolphins truly are and do, as well as understand some of the controversies surrounding them. While raising compelling questions, the book provides a wealth of information on a legendary species that is loved and admired by many people.John E. Reynolds, professor of marine science at Eckerd College, St. Petersburg, Florida, is chair of the U.S. Marine Mammal Commission. He has written over 100 articles on marine mammal biology and conservation and is coauthor with Daniel K. Odell of "Manatees and Dugongs"and coeditor of "Biology of Marine Mammals."Randall S. Wells is a behavioral ecologist with the Conservation Biology Department of the Chicago Zoological Society and adjunct associate professor of ocean sciences at the University of California, Santa Cruz. He also serves as director of the Center for Marine Mammal and Sea Turtle Research at Mote Marine Laboratory, Sarasota, Florida, where he conducts the world s longest running study of wild dolphins.Samantha D. Eide, a graduate student at the University of South Florida, is field leader for the Eckerd College Dolphin Project, St. Petersburg, Florida."
