Immunology of marine mammals is a relatively understudied field and its monitoring plays an important role in the individual and group management of these animals, along with an increasing value as ...an environmental health indicator. This study was aimed at implementing the knowledge on the immune response in cetaceans stranded along the Italian coastline to provide a baseline useful for assessing the immune status of bottlenose (
) and striped (
) dolphins. In particular, since the Mediterranean Sea is considered a heavily polluted basin, a comparison with animals living in open waters such as the Atlantic Ocean was made. Formalin-fixed, paraffin-embedded spleen, thymus, and lymph node tissues from 16 animals stranded along Italian and 11 cetaceans from the Canary Island shores were sampled within 48 h from death. Information regarding stranding sites, gender, and age as well as virologic, microbiological, and parasitological investigations, and the cause and/or the death mechanism were also collected in order to carry out statistical analyses. Selected tissues were routinely stained with hematoxylin-eosin (H&E) and with immunohistochemical techniques (IHC). For IHC analysis, anti-human CD5 monoclonal mouse antibody to identify T lymphocytes, CD20 monoclonal mouse antibody for the identification of mature B lymphocytes and HLA-DR antigen (alpha-chain) monoclonal mouse antibody for the identification of the major histocompatibility complex type II were previously validated for both species by Western-blotting technique.
-test method applied to quantitative evaluation of IHC positive cells showed a significant relationship between the number of (expression) of CD20 stained lymphocytes and normal and hypoplastic lymph nodes, respectively. No other significant correlations were noticed. Analyses for organochlorines (OC) compounds were performed in animals (n°5) having frozen blubber tissue available. A simple linear regression was calculated to predict if the amount of OCs could influence the number of inflammatory cell subpopulations and a moderate negative correlation was found between the presence of high quantity of contaminants and the number of T lymphocytes. Future analysis should be aimed to understand the effect of the major immunomodulatory pathogens on sub-populations of B and T cells.
Common bottlenose dolphins (Tursiops truncatus) inhabit bays, sounds and estuaries across the Gulf of Mexico. Following the Deepwater Horizon oil spill, studies were initiated to assess potential ...effects on these ecologically important apex predators. A previous study reported disease conditions, including lung disease and impaired stress response, for 32 dolphins that were temporarily captured and given health assessments in Barataria Bay, Louisiana, USA. Ten of the sampled dolphins were determined to be pregnant, with expected due dates the following spring or summer. Here, we report findings after 47 months of follow-up monitoring of those sampled dolphins. Only 20% (95% CI: 2.50–55.6%) of the pregnant dolphins produced viable calves, as compared with a previously reported pregnancy success rate of 83% in a reference population. Fifty-seven per cent of pregnant females that did not successfully produce a calf had been previously diagnosed with moderate–severe lung disease. In addition, the estimated annual survival rate of the sampled cohort was low (86.8%, 95% CI: 80.0–92.7%) as compared with survival rates of 95.1% and 96.2% from two other previously studied bottlenose dolphin populations. Our findings confirm low reproductive success and high mortality in dolphins from a heavily oiled estuary when compared with other populations. Follow-up studies are needed to better understand the potential recovery of dolphins in Barataria Bay and, by extension, other Gulf coastal regions impacted by the spill.
There are few cetacean tissue-specific polycyclic aromatic hydrocarbon (PAH) concentration studies in the Mediterranean, despite this region is among the most subjected to chemical contamination. PAH ...analyses were conducted in different tissues of striped dolphins (Stenella coeruleoalba, N = 64) and bottlenose dolphins (Tursiops truncatus, N = 9) stranded along the French Mediterranean coastline from 2010 to 2016. Comparable levels were measured in S. coeruleoalba and T. trucantus (1020 and 981 ng g−1 lipid weight in blubber, 228 and 238 ng g−1 dry weight in muscle, respectively). The results suggested a slight effect of maternal transfer. The greatest levels were recorded by urban and industrial centers, and decreasing temporal trends were observed in males muscle and kidney, but not in other tissues. As a conclusion, the elevated levels measured could represent a serious threat to dolphins populations in this region, particularly by urban and industrial centers.
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•PAH were elevated in Stenella coeruleoalba and Tursiops truncatus.•Lower levels in S. coeruleoalba females suggest little maternal transfer.•Naphthalene, fluorene, 5- and 6-rings PAHs dominated in all tissues.•Highest levels were localized by urban and industrial areas.•Constant time trends in blubber and liver, possibly decreasing in muscle and kidney.
The bottlenose dolphin, genus Tursiops is one of the best studied of all the Cetacea with a minimum of two species widely recognised. Common bottlenose dolphins (T. truncatus), are the cetacean ...species most frequently held in captivity and are known to hybridize with species from at least 6 different genera. In this study, we document several intra-generic hybridization events between T. truncatus and T. aduncus held in captivity. We demonstrate that the F.sub.1 hybrids are fertile and can backcross producing apparently healthy offspring, thereby showing introgressive inter-specific hybridization within the genus. We document that female F.sub.1 hybrids can reach sexual maturity at 4 yr and 3 mo of age, and can become pregnant and give birth before being fully weaned. The information presented has implications for understanding hybrid reticulation among cetacean species and practical implications for captive facilities housing either Tursiops species or hybrids thereof.
Individuals and groups within the same population may differ in their use of resources. Also referred to as niche specialization, such differences can be documented through direct or indirect ...observation of resource or habitat use. Here, we examined selective habitat use in alliance-forming male Indo-Pacific bottlenose dolphins, Tursiops aduncus, in Shark Bay, Western Australia. Using 6 years of sighting data (2001–2006), we calculated the home ranges of 17 male alliances (comprising 3–14 individuals each). We defined five habitat types in the study area and measured the proportion of each habitat type in the home range of each alliance. Habitat selectivity was examined using selection ratios of used and available habitat within alliance home ranges. Since home range is also a form of habitat selection, we also examined selection ratios of alliances within defined subareas within the study area. Subareas were the combined home ranges of subsets of alliances that were linked by general location, distinctive habitat features and seasonal movement patterns. During each sighting, the predominant group behaviour was recorded. We analysed data from all sightings (which included all behavioural types: resting, travelling, socializing and foraging), as well as a restricted set of foraging groups only. For all sightings, alliances were selective of habitat within each of three subareas (northern, central, southern), and 14 alliances were selective of habitat within their home range. For foraging sightings, alliances within all three subareas were selective with respect to foraging habitat, and seven alliances showed significant selection of foraging habitat within their respective home ranges. Some alliances with broadly overlapping ranges foraged in different habitats. Alliance-specific habitat use may be influenced by ecological and social factors. Our results raise the possibility that the considerable variation in alliance size within this population may be influenced by the distribution of food as well as the distribution of females.
•Niche specialization can occur among individuals and groups within populations.•Male dolphin alliances (each of 3–14 members) cooperate to secure oestrous females.•Alliances inhabit overlapping ranges with similar proportions of available habitats.•Alliances with overlapping ranges and similar habitats forage in different habitats.•Thus food, as well as females, may explain marked differences in alliance tactics.
Human caregivers interacting with children typically modify their speech in ways that promote attention, bonding, and language acquisition. Although this "motherese," or child-directed communication ...(CDC), occurs in a variety of human cultures, evidence among nonhuman species is very rare. We looked for its occurrence in a nonhuman mammalian species with long-term mother-offspring bonds that is capable of vocal production learning, the bottlenose dolphin (
). Dolphin signature whistles provide a unique opportunity to test for CDC in nonhuman animals, because we are able to quantify changes in the same vocalizations produced in the presence or absence of calves. We analyzed recordings made during brief catch-and-release events of wild bottlenose dolphins in waters near Sarasota Bay, Florida, United States, and found that females produced signature whistles with significantly higher maximum frequencies and wider frequency ranges when they were recorded with their own dependent calves vs. not with them. These differences align with the higher fundamental frequencies and wider pitch ranges seen in human CDC. Our results provide evidence in a nonhuman mammal for changes in the same vocalizations when produced in the presence vs. absence of offspring, and thus strongly support convergent evolution of motherese, or CDC, in bottlenose dolphins. CDC may function to enhance attention, bonding, and vocal learning in dolphin calves, as it does in human children. Our data add to the growing body of evidence that dolphins provide a powerful animal model for studying the evolution of vocal learning and language.
Historically, the taxonomic status of the bottlenose dolphins, Tursiops, has been confusing. Over 20 nominal species have been described in, or transferred to, the genus, but most them have been ...synonymized under T. truncatus, the type species of the genus. Here, we review the taxonomic status of Tursiops gephyreusLahille, 1908, from the southwestern Atlantic Ocean (SWA), a taxon long considered as either synonym or subspecies of T. truncatus. We examined a total of 280 bottlenose dolphin skulls, including the lectotype of T. gephyreus. We examined all specimens for morphological (14 characters) and morphometric (29 measurements) differences. Univariate and multivariate analyses were conducted to test differences between groups. Based on qualitative and quantitative analyses of skulls as well as the vertebrae number of Tursiops specimens from SWA, we recognized 2 distinct morphological forms of bottlenose dolphins in the region, consistent with treatment of 2 species under the “diagnosable version of the Phylogenetic Species Concept.” Six qualitative characters are reliable for the identification of both species in the SWA, but the shape of the nasal process of the right premaxilla alone is sufficient to separate the species. Furthermore, the total number of vertebrae is higher in T. truncatus (62–64) than in T. gephyreus (57–59). Based on these results, we propose the revalidation of T. gephyreus. Since T. gephyreus was recognized as inhabiting the estuaries and the surf zone alongside the Rio Grande do Sul in Brazil, Uruguay, and Argentina coasts, the conservation efforts must take into account that this region presents similar threats to the species.
Understanding to what extent the living world will be affected by climate change is still to be achieved, especially in the sea. Thus, exploring in marine species the direction and timing of shifts ...in space use and movements related to climate changes should be considered a priority. In the present study, through a correlative approach, we investigated the influence of temperature and marine heat waves (MHWs) on the spatial traits (local occurrence and home range) of a small common bottlenose dolphin population in the Mediterranean Sea by analyzing 560 sightings from 2013 to 2020. The increase in sea surface temperature (SST) negatively influenced both dolphin occurrence and group size in the study area. Furthermore, regardless of the sex and social unit to which the animals belong, in July–September 2017–2020 individual home range size increased threefold (on average from 5 to 15 km2) compared to 2013–2016, when SST was on average 1.34 °C lower and MHWs shorter of 29 days/year. These results can help forecasting the range of consequences of warming effects and to assist local management efforts, in terms of marine protected areas design and management, suggesting that an integrated multi-level approach that examines the influence of warming on dolphin spatial traits together with the abundance and distribution of prey populations and ecological status of foraging habitats (such as the seagrass beds) could be useful in mitigating the effects of climate change on coastal dolphins.
•High sea surface temperature influences dolphin occurrence and group size.•Warming and long marine heat waves are related to the increase of home range size.•Evidence on dolphin spatial traits may assist management efforts.
Citizen science projects are an advantageous method to carry out research in the marine environmental field, especially concerning high mobile and often elusive species like cetaceans, allowing the ...collection of data in wide spatial-temporal scale. This project aims to validate the feasibility and accuracy of cetacean monitoring program through the citizen science approach and to test the efficiency of this method to large scale study area. In this work data obtained by researchers monitoring were compared with data coming from citizen, which followed specifically developed protocol. Data collected were used to investigate the presence and distribution of bottlenose dolphins (Tursiops truncatus) in the Sicilian Channel and to evaluate the contribution of citizen scientist to improve knowledge about species, in this case for bottlenose dolphin a vulnerable species listed in the Annex II of Habitat Directive (92/43 CE). The results show that citizen dataset contributes to increase the distribution map of the 22% more than only research data were considered. Citizen science programme results useful to gain information in small areas not monitored by scientific programs, such as in this study, and they would be very useful if applied at large-scale. The promotion of citizen science programs in specified small areas could be helpful to cover unmonitored zones, to gain preliminary results and bridge the gap of knowledge about species occurrence and distribution. For this reason, citizen support might help competent authorities to answer to the environmental policies as Habitat Directive and Marine Strategy Framework Directive. This study is a demonstration of how citizen can encourage scientists to start long-term research project in not regularly monitored areas.
•18 cetacean sightings were reported by citizen and 7 by research monitoring.•Recreational fishermen and pleasure boaters were the most participative.•Research dataset results in 1 dolphin core-area of 356 km 2 at 30–40 m depths.•Citizen dataset results in 3 dolphin core-areas of 98 km 2 inshore, at 20 m depths.•Citizen contributes to increase knowledge on dolphin distribution of the 22%.
Understanding the impact of human disturbance on wildlife populations is of societal importance,1 with anthropogenic noise known to impact a range of taxa, including mammals,2 birds,3 fish,4 and ...invertebrates.5 While animals are known to use acoustic and other behavioral mechanisms to compensate for increasing noise at the individual level, our understanding of how noise impacts social animals working together remains limited. Here, we investigated the effect of noise on coordination between two bottlenose dolphins performing a cooperative task. We previously demonstrated that the dolphin dyad can use whistles to coordinate their behavior, working together with extreme precision.6 By equipping each dolphin with a sound-and-movement recording tag (DTAG-37) and exposing them to increasing levels of anthropogenic noise, we show that both dolphins nearly doubled their whistle durations and increased whistle amplitude in response to increasing noise. While these acoustic compensatory mechanisms are the same as those frequently used by wild cetaceans,8,9,10,11,12,13 they were insufficient to overcome the effect of noise on behavioral coordination. Indeed, cooperative task success decreased in the presence of noise, dropping from 85% during ambient noise control trials to 62.5% during the highest noise exposure. This is the first study to demonstrate in any non-human species that noise impairs communication between conspecifics performing a cooperative task. Cooperation facilitates vital functions across many taxa and our findings highlight the need to account for the impact of disturbance on functionally important group tasks in wild animal populations.
•Anthropogenic noise impairs behavioral coordination in a cooperative context•Dolphins modified their vocal signals to facilitate cooperative success•Acoustic compensatory mechanisms are insufficient for overcoming noise impacts•Critical to account for noise impacts on collective tasks in wild animals
Anthropogenic noise impairs cooperative success in bottlenose dolphins. Sørensen et al. show that acoustic and other behavioral compensatory mechanisms are insufficient for overcoming the effects of noise on communication. This highlights the need to account for noise disturbance on functionally important group tasks in wild animal populations.
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