First confirmed reports of the isolation of Brucella ceti from a Risso's dolphin Grampus griseus and a killer whale Orcinus orca.

Brucella ceti has been recovered from a number species of cetaceans worldwide over the last 25 yr. Here we report, for the first time, the recovery of B. ceti from a Risso's dolphin Grampus griseus and a killer whale Orcinus orca. Recovery from an abdominal mass in the dolphin provides further evidence of the systemic pathogenic potential for B. ceti infection in cetaceans. The isolation of B. ceti ST23 (porpoise cluster) from a killer whale from a group known to eat other marine mammals raises the possibility of infection via ingestion. This report takes the number of cetacean species in UK coastal waters from which B. ceti has been isolated to 11 and highlights the value of routine, comprehensive and specific screening for significant pathogens such as Brucella sp. by strandings networks.

Risso's dolphins plan foraging dives.

Humans remember the past and use that information to plan future actions. Lab experiments that test memory for the location of food show that animals have a similar capability to act in anticipation of future needs, but less work has been done on animals foraging in the wild. We hypothesized that planning abilities are critical and common in breath-hold divers who adjust each dive to forage on prey varying in quality, location and predictability within constraints of limited oxygen availability. We equipped Risso's dolphins with sound-and-motion recording tags to reveal where they focus their attention through their externally observable echolocation and how they fine tune search strategies in response to expected and observed prey distribution. The information from the dolphins was integrated with synoptic prey data obtained from echosounders on an underwater vehicle. At the start of the dives, whales adjusted their echolocation inspection ranges in ways that suggest planning to forage at a particular depth. Once entering a productive prey layer, dolphins reduced their search range comparable to the scale of patches within the layer, suggesting that they were using echolocation to select prey within the patch. On ascent, their search range increased, indicating that they decided to stop foraging within that layer and started searching for prey in shallower layers. Information about prey, learned throughout the dive, was used to plan foraging in the next dive. Our results demonstrate that planning for future dives is modulated by spatial memory derived from multi-modal prey sampling (echoic, visual and capture) during earlier dives.

Manganese Concentrations in Tissues and Skin of Three Dolphin Species Stranded in the Croatian Waters of the Adriatic Sea from 1995 to 2013.

Manganese concentrations were determined in muscle, kidney, liver, spleen, lung and fat tissues and skin of three cetacean species, the bottlenose (Tursiops truncatus), striped (Stenella coeruleoalba) and Risso's (Grampus griseus) dolphins, stranded along the Croatian Adriatic coast between 1995 and 2013. Mean ranges determined in tissues were (mg/kg, ww): muscle 0.23-0.27, liver 2.87-4.00, kidney 0.66-1.26, spleen 0.37-0.79, lung 0.18-0.57, skin 0.11-0.97, fat 0.06-0.42. The highest Mn mean levels in tissues were measured in species (mg/kg, ww): T. truncates lung 0.41, skin 0.97, fat 0.42; S. coeruleoalba muscle 0.26; G. griseus kidney 1.26, liver 4.00, spleen 0.64. Significant differences of Mn concentrations in the liver (p = 0.034), spleen (p = 0.037) and skin (p = 0.013) were found among the three dolphin species. Significant differences in Mn levels were found between young and adult T. truncates in kidney (p = 0.042), lung (p = 0.0040) and skin (p = 0.0034).

Evidence suggests vocal production learning in a cross-fostered Risso's dolphin (Grampus griseus).

Vocal learning is a rare skill in mammals, and we have limited information about the contexts in which they use it. Previous studies suggested that cetaceans in general are skilled at imitating sounds, but only few species have been studied to date. To expand this investigation to another species and to investigate the possible influence of the social environment on vocal learning, we studied the whistle repertoire of a female Risso's dolphin (Grampus griseus) that was stranded at an early age and was subsequently raised in a group of bottlenose dolphins (Tursiops truncatus). We show that this cross-fostered animal produced vocal signals more akin to those of its Tursiops poolmates than those of Risso's dolphins in the wild. This is one of very few systematic cross-fostering studies in cetaceans and the first to suggest vocal production learning in the Risso's dolphin. Our findings also suggest that social experience is a major factor in the development of the vocal repertoire in this species.

Risso's Dolphin, Grampus griseus, in the Western Ligurian Sea: Trends in Population Size and Habitat Use.

This paper provides a summary of 25 years of research on Risso's dolphins (Grampus griseus) in the western Ligurian Sea. Seasonal variations in abundance, distribution and habitat use were observed. Photographic mark-recapture methods provided a population size estimate for the period from 1998 to 2012, of about 100 individuals (95% CI of 60-220 individuals). The same methods detected a decline in population size from an average of about 120-150 from 2000 to 2005, to an average of 70-100 during 2010 to 2014. Species occurrence appeared to be significantly decreasing in coastal and continental slope areas, while it seemed to be stable in the most pelagic area. In addition, a dramatic change was observed in the local primary production, which was analysed based on time series of sea surface temperature and chlorophyll data from 1990 to 2014. Based on fisheries landings, there may have been a general decrease in fishery productivity, both in the western Ligurian Sea and in adjacent regions. Environmental variability, depletion of resources by fisheries and possibly interspecies competition may all have contributed to cause changes in Risso's dolphin habitat use and occurrence in the western Ligurian Sea.

Dolphins in a Scaled-Down Mediterranean: The Gulf of Corinth's Odontocetes.

The Gulf of Corinth is a 2400-km2 semi-enclosed inland system (a mediterraneus) in central Greece. Its continental shelf areas, steep bottom relief, and waters up to 500-900m deep offer suitable habitat to neritic and pelagic species. We used photographic capture-recapture, distribution modelling, and direct observations to investigate the abundance, status, habitat preferences, movements, and group size of four odontocete species regularly observed in the Gulf, based on five years (2011-2015) of survey effort from small boats. Striped dolphins (Stenella coeruleoalba) are more abundant (1324 individuals, 95%CI 1158-1515) than was determined from previous estimates. Striped dolphins appear to be confined to the Gulf, where they favour deep and oligotrophic waters, and were encountered in single-species and mixed-species groups. Short-beaked common dolphins (Delphinus delphis) (22 individuals, 95%CI 16-31), individuals with intermediate pigmentation (possibly striped/common dolphin hybrids) (55, 95%CI 36-83), and a single Risso's dolphin (Grampus griseus) were only encountered in mixed-species groups with striped dolphins. Short-beaked common dolphins constitute a discrete conservation unit (subpopulation), and based on the current estimate, would qualify as Critically Endangered according to International Union for the Conservation of Nature (IUCN) Red List criteria. Common bottlenose dolphins (Tursiops truncatus) (39 animals, 95%CI 33-47) occur in single-species groups; they prefer continental shelf waters and areas near fish farms in the northern sector, and several animals appear to move into and out of the Gulf. Additionally, we contribute records of marine fauna and an assessment of the fishing fleet operating in the Gulf. Our study shows that the importance of this vulnerable marine environment has been underestimated, and management action must be taken to mitigate human impact and ensure long-term protection.

Context-driven communication during deep-sea foraging in a social toothed whale.

Social deep-diving odontocetes face the challenge of balancing near-surface proximity to oxygen and group members with foraging in the deep sea. Individuals rely on conspecifics for critical life functions, such as predator defence, but disperse during foraging to feed individually. To understand the role of social acoustic mediation during foraging in deep-diving toothed whales, we investigated the context of social burst-pulse call production in Risso's dolphin (Grampus griseus) using biologgers. Dolphins produced context-specific burst pulses predominantly during daytime foraging, preceding or following foraging dives and in the early descent of daytime deep dives. Individuals applied differential short and long burst-pulse calls intended for either near-surface receivers (horizontal transmission) or deep-foraging receivers (vertical transmission). Our results show that deep-diving toothed whales are reliant on acoustic communication during certain foraging contexts, to relay information including foraging conditions or an individual's location. Moreover, they accentuate the importance of maintaining acoustic contact with conspecifics, specifically when dispersed during deeper foraging. It also signifies that our oceanic top predators may be specifically vulnerable to the current strong increase in anthropogenic noise. Potential masking of the signals from group members communicating at a distance could undermine their social cohesion, and hence their capacity to maintain vital life functions.

Comparative Study of the Gastric Mucosa of Risso's Dolphin (Grampus griseus) and Bottlenose Dolphin (Tursiops truncatus): A Key to Manage the Diet in Captive Conditions.

To histologically evaluate the gastric compartments of Risso's (Grampus griseus) and bottlenose dolphins (Tursiops truncatus) and provide suggestions for the diet of Risso's dolphins in captivity, we examined 12 stomachs from both species. While slight differences in keratinization were observed in the forestomach, significant differences came to light in the second stomach's mucosa. At this level, in Risso's dolphin, the principal cells are markedly reduced in size and located externally to the parietal cells, not interspersed between them, compared to bottlenose dolphins; differences were also observed in the structure and concentration of the parietal and principal cells of the gastric body glands (p < 0.0001). The quantitative results of G- and D-cell counts in the gastric mucosa show a clear difference, with a higher concentration of G cells in the mucosa of Risso's dolphin (t = 7.334; p < 0.0001) and a higher level of D cells in bottlenose dolphin mucosa (t = 3.123; p = 0.0049). These results suggest that parietal cells undergo greater stimulation by gastrin produced by G cells, with greater acid secretion in G. griseus. Further studies are needed to understand whether an inappropriate diet could lead to severe clinical signs due to gastric acidity in Risso's dolphin.

Risso's dolphins perform spin dives to target deep-dwelling prey.

Foraging decisions of deep-diving cetaceans can provide fundamental insight into food web dynamics of the deep pelagic ocean. Cetacean optimal foraging entails a tight balance between oxygen-conserving dive strategies and access to deep-dwelling prey of sufficient energetic reward. Risso's dolphins (Grampus griseus) displayed a thus far unknown dive strategy, which we termed the spin dive. Dives started with intense stroking and right-sided lateral rotation. This remarkable behaviour resulted in a rapid descent. By tracking the fine-scale foraging behaviour of seven tagged individuals, matched with prey layer recordings, we tested the hypothesis that spin dives are foraging dives targeting deep-dwelling prey. Hunting depth traced the diel movement of the deep scattering layer, a dense aggregation of prey, that resides deep during the day and near-surface at night. Individuals shifted their foraging strategy from deep spin dives to shallow non-spin dives around dusk. Spin dives were significantly faster, steeper and deeper than non-spin dives, effectively minimizing transit time to bountiful mesopelagic prey, and were focused on periods when the migratory prey might be easier to catch. Hence, whereas Risso's dolphins were mostly shallow, nocturnal foragers, their spin dives enabled extended and rewarding diurnal foraging on deep-dwelling prey.

Endoscopic Study of the Oral and Pharyngeal Cavities in the Common Dolphin, Striped Dolphin, Risso's Dolphin, Harbour Porpoise and Pilot Whale: Reinforced with Other Diagnostic and Anatomic Techniques.

In this work, the fetal and newborn anatomical structures of the dolphin oropharyngeal cavities were studied. The main technique used was endoscopy, as these cavities are narrow tubular spaces and the oral cavity is difficult to photograph without moving the specimen. The endoscope was used to study the mucosal features of the oral and pharyngeal cavities. Two pharyngeal diverticula of the auditory tubes were discovered on either side of the choanae and larynx. These spaces begin close to the musculotubaric channel of the middle ear, are linked to the pterygopalatine recesses (pterygoid sinus) and they extend to the maxillopalatine fossa. Magnetic Resonance Imaging (MRI), osteological analysis, sectional anatomy, dissections, and histology were also used to better understand the function of the pharyngeal diverticula of the auditory tubes. These data were then compared with the horse's pharyngeal diverticula of the auditory tubes. The histology revealed that a vascular plexus inside these diverticula could help to expel the air from this space to the nasopharynx. In the oral cavity, teeth remain inside the alveolus and covered by gums. The marginal papillae of the tongue differ in extension depending on the fetal specimen studied. The histology reveals that the incisive papilla is vestigial and contain abundant innervation. No ducts were observed inside lateral sublingual folds in the oral cavity proper and caruncles were not seen in the prefrenular space.

Dolphins Stranded along the Tuscan Coastline (Central Italy) of the "Pelagos Sanctuary": A Parasitological Investigation.

Parasite monitoring is considered a necessary step for cetacean management and conservation. Between February 2013 and July 2015, 26 dolphins (15 Stenella coeruleoalba, 10 Tursiops truncatus, and one Grampus griseus) stranded along the Tuscan coastline of the protected marine area "Pelagos Sanctuary", were examined. Organs, tissues, and faecal and blood samples taken from all animals were analysed by parasitological, immunological, and molecular techniques. Twenty-one out of 26 dolphins (80.77%) tested positive for at least one parasite species, and 13/15 (86.7%) S. coeruleoalba, 7/10 (70%) T. truncatus, and the single G. griseus were found positive. Identified parasites included the nematodes Skrjabinalius guevarai (7.69%, 2/26), Halocercus lagenorhynchi (3.85%, 1/26), Halocercus delphini (7.69%, 2/26), Stenurus ovatus (7.69%, 2/26), Crassicauda spp. (7.69%, 2/26); the trematodes Pholeter gastrophilus (26.92%, 7/26), Campula palliata (3.85%, 1/26); the cestodes Phyllobothrium delphini (42.31%, 11/26), Monorygma grimaldii (23.08%, 6/26), Tetrabothrium forsteri (7.69%, 2/26), Strobilocephalus triangularis (7.69%, 2/26), and the acanthocephalan Bolbosoma vasculosum (7.69%, 2/26). Moreover, 6/26 (23%) animals scored positive to Toxoplasma gondii at serology, but PCR confirmed the infection (T. gondii Type II genotype) in a single animal. In examined dolphins, obtained results showed a high prevalence of endoparasites, which included species considered as a cause of severe debilitation or death.